Jasmonates （JAs） are plant hormones with essential roles in plant defense and development. The basic- helix-loop-helix （bHLH） transcription factor （TF） MYC2 has recently emerged as a master regulator of most asp...Jasmonates （JAs） are plant hormones with essential roles in plant defense and development. The basic- helix-loop-helix （bHLH） transcription factor （TF） MYC2 has recently emerged as a master regulator of most aspects of the jasmonate （JA） signaling pathway in Arabidopsis. MYC2 coordinates JA-mediated defense responses by antagonistically regulating two different branches of the JA signaling pathway that determine resistance to pests and pathogens, respectively. MYC2 is required for induced systemic resistance （ISR） triggered by beneficial soil microbes while MYC2 function is targeted by pathogens during effector-mediated suppression of innate immunity in roots. Another notable function of MYC2 is the regulation of crosstalk between the signaling pathways of JA and those of other phytohormones such as abscisic acid （ABA）, salicylic acid （SA）, gibberellins （GAs）, and auxin （IAA）. MYC2 also regulates interactions between JA signaling and light, phytochrome signaling, and the circadian clock, MYC2 is involved in JA-regulated plant development, lateral and adventitious root formation, flowering time, and shade avoidance syndrome. Related bHLH TFs MYC3 and MYC4 also regulate both overlapping and distinct MYC2-regulated functions in Arabidopsis while MYC2 orthologs act as ＇master switches＇ that regulate JA-mediated biosynthesis of secondary metabolites. Here, we briefly review recent studies that revealed mechanistic new insights into the mode of action of this versatile TF.展开更多
The small phenolic compound salicylic acid （SA） plays an important regulatory role in multiple physiological processes including plant im- mune response. Significant progress has been made during the past two decade...The small phenolic compound salicylic acid （SA） plays an important regulatory role in multiple physiological processes including plant im- mune response. Significant progress has been made during the past two decades in understanding the SA-mediated defense signaling network. Characterization of a number of genes functioning in SA biosynthesis, conjugation, accumulation, signaling, and crosstalk with other hormones such as jasmonic acid, ethylene, abscisic acid, auxin, gibberellic acid, cytokinin, brassinosteroid, and peptide hormones has sketched the finely tuned immune response network. Full understanding of the mech- anism of plant immunity will need to take advantage of fast developing genomics tools and bioinformatics techniques. However, elucidating genetic components involved in these pathways by conventional ge- netics, biochemistry, and molecular biology approaches will continue to be a major task of the community. High-throughput method for SA quantification holds the potential for isolating additional mutants related to SA-mediated defense signaling.展开更多
Growth-defense tradeoffs are thought to occur in plants due to resource restrictions, which demand prior- itization towards either growth or defense, depending on external and internal factors. These tradeoffs have pr...Growth-defense tradeoffs are thought to occur in plants due to resource restrictions, which demand prior- itization towards either growth or defense, depending on external and internal factors. These tradeoffs have profound implications in agriculture and natural ecosystems, as both processes are vital for plant survival, reproduction, and, ulti- mately, plant fitness. While many of the molecular mechanisms underlying growth and defense tradeoffs remain to be elucidated, hormone crosstalk has emerged as a major player in regulating tradeoffs needed to achieve a balance. In this review, we cover recent advances in understanding growth-defense tradeoffs in plants as well as what is known regard- ing the underlying molecular mechanisms. Specifically, we address evidence supporting the growth-defense tradeoff concept, as well as known interactions between defense signaling and growth signaling. Understanding the molecular basis of these tradeoffs in plants should provide a foundation for the development of breeding strategies that optimize the growth-defense balance to maximize crop yield to meet rising global food and biofuel demands.展开更多
Protein folding in the endoplasmic reticulum （ER） is a fundamental process in plant cells that is vulnerable to many environmental stresses. When unfolded or misfolded proteins accumulate in the ER, the well-conserv...Protein folding in the endoplasmic reticulum （ER） is a fundamental process in plant cells that is vulnerable to many environmental stresses. When unfolded or misfolded proteins accumulate in the ER, the well-conserved unfolded protein response （UPR） is initiated to mitigate the ER stress by enhancing the protein folding capability and/or accelerating the ER-associated protein degradation. Here, we report the conservation of the activation mechanism of OsbZIP74 （also known as OsbZIP50）, an important ER stress regulator in monocot plant rice （Oryza sativa L.）. Under normal conditions, OsbZIP74 mRNA encodes a basic leucine-zipper transcription factor with a putative transmembrane domain. When treating with ER stress-inducing agents such as tunicamycin and DTT, the conserved double stem-loop structures of OsbZIP74 mRNA are spliced out. Thereafter, the resulting new OsbZIP74 mRNA produces the nucleus-localized form of OsbZIP74 protein, eliminating the hydrophobic region. The activated form of OsbZIP74 has transcriptional activation activity in both yeast cells and Arabidopsis leaf protoplasts. The induction of OsbZIP74 splicing is much suppressed in the OsIRE1 knock- down rice plants, indicating the involvement of OslRE1 in OsbZIP74 splicing. We also demonstrate that the unconventional splicing of OsbZIP74 mRNA is associated with heat stress and salicylic acid, which is an important plant hormone in systemic acquired resistance against pathogen or parasite.展开更多
Salicylic acid （SA） was an essential component of the plant resistance to pathogens and also plays an important role in mediating plant response to some abiotic stress. The possible effects of SA on the growth and H...Salicylic acid （SA） was an essential component of the plant resistance to pathogens and also plays an important role in mediating plant response to some abiotic stress. The possible effects of SA on the growth and H2O2-metabolizing enzymes in rice seedlings under lead stress were studied. When rice seedlings grown in nutrient solution containing Pb^2＋ （0, 0.05, 0.15, 0.25 mmol/L） for 18 d, the plant biomass as well as the chlorophyll content of leaves decreased with increasing Pb concentration. The pre-treatment with SA （treated with 0.1 mmol/L SA for 48 h before Pb stress） partially protected seedlings from Pb toxicity. The chlorophyll contents were significant higher in leaves of Pb-exposed with SA pre-treatment seedlings than in Pb-exposed plants at the same Pb intensity. SA pre-treated alone could significantly increase the length of shoot and root of seedlings but the vigour difference was not marked under long-term exposure to Pb toxicity. SA pre-treated influence the H2O2 level in leaves of seedlings by up-regulating the activity of superoxide dismutase （SOD）, repressing the activity of catalase （CAT） and ascorbate peroxidase （APX） depending on the concentrations of Pb^2＋ in the growth medium. The results supported the conclusion that SA played a positive role in rice seedlings against Pb toxicity.展开更多
Old leaves of wild-type rice plants （Oryza sativa L. cv. Nipponbare） are more resistant to blast fungus （Magnaporthe grisea） than new leaves. In contrast, both old and new leaves of the rice phytochrome triple mut...Old leaves of wild-type rice plants （Oryza sativa L. cv. Nipponbare） are more resistant to blast fungus （Magnaporthe grisea） than new leaves. In contrast, both old and new leaves of the rice phytochrome triple mutant （phyAphyBphyC） are susceptible to blast fungus. We demonstrate that pathogenesis-related class 1 （PR1） proteins are rapidly and strongly induced during M. grisea infection and following exogenous jasmonate （JA） or salicylic acid （SA） exposure in the old leaves, but not in the new leaves of the wild-type. In contrast, the accumulation of PR1 proteins was significantly attenuated in old and new leaves of the phyAphyBphyC mutant. These results suggest that phytochromes are required for the induction of PR1 proteins in rice. Basal transcription levels of PRla and PRlb were substantially higher in the wildtype as compared to the phyAphyBphyC mutant, suggesting that phytochromes also are required for basal expression of PR1 genes. Moreover, the transcript levels of genes known to function in SA- or JA-dependent defense pathways were regulated by leaf age and functional phytochromes. Taken together, our findings demonstrate that phytochromes are required in rice for age-related resistance to M. grisea and may indirectly increase PR1 gene expression by regulating SA- and JA-dependent defense pathways.展开更多
The possible physiological mechanism of enhancement of cold tolerance by salicylic acid (SA) in banana seedlings ( Musa acuminata cv. Williams 8188) was explored. Measurements of leakage electrolyte after 2 d of re...The possible physiological mechanism of enhancement of cold tolerance by salicylic acid (SA) in banana seedlings ( Musa acuminata cv. Williams 8188) was explored. Measurements of leakage electrolyte after 2 d of recovery at 30/22 ℃ (day/night) following 3 d of cold stress at 7 ℃ showed that pretreatment with hydroponic solution containing SA 0.3-0.9 mmol/L as foliar spray under normal growth conditions (30/22 ℃) could significantly enhance cold tolerance of banana plants. The highest enhancing effect of SA occurred at 0.5 mmol/L and it showed the lowest leakage rate of electrolyte or smaller leaf wilting area after 2 d of recovery at normal temperature from 3 d of 7 ℃ or 5 ℃ cold stress. Higher concentrations (≥2.5 mmol/L) of SA, however, caused more electrolyte leakage, indicating that they aggravated chilling damage. Enhanced cold tolerance by SA could be related to H 2O 2 metabolism. Compared with water_treated seedlings (control), SA 0.5 mmol/L treatment inhibited activities of catalase (CAT) and ascorbate peroxidase (APX), increased peroxidase (POX) activity, but did not affect the activity of superoxide dismutase (SOD) under normal growth conditions, and these changes might lead to an accumulation of H 2O 2, whereas SA pretreatment enhanced the activities of CAT and APX, and reduced the increase in productions of H 2O 2 and thiobarbituric acid_reaction substances (TBARS) during subsequent 7 ℃ cold stress and recovery periods. Exogenous H 2O 2 treatments (1.5 -2.5 mmol/L) also increased cold tolerance of banana seedlings. Furthermore, pretreatment of banana seedlings with dimethylthiourea (a trap for H 2O 2) significantly inhibited cold tolerance induced by SA. These results suggested that endogenous H 2O 2 may be required for SA_enhanced cold tolerance. The significance of the interaction of SA, H 2O 2 and H 2O 2_metabolizing enzymes during cold stress has been discussed.展开更多
Rapid and dynamic change in hydrogen peroxide （H2O2） levels can serve as an important signal to regulate various biological processes in plants. The change is realized by tilting the balance between its production a...Rapid and dynamic change in hydrogen peroxide （H2O2） levels can serve as an important signal to regulate various biological processes in plants. The change is realized by tilting the balance between its production and scavenging rates, in which membrane-associated NADPH oxidases are known to play a crucial role. Functioning independently from NADPH oxidases, glycolate oxidase （GLO） was recently demonstrated as an aitemative source for H2O2 production during both germ-for-germ and non-host resistance in plants. In this study, we show that GLO physically interacts with catalase （CAT） in rice leaves, and that the interaction can be deregulated by salicylic acid （SA）. Furthermore, the GLO-mediated H2O2 accumulation is synergistically enhanced by SA. Based on the well-known mechanism of substrate channeling in enzyme complexes, SA-induced H2O2 accumulation likely results from SA-induced GLO-CAT dissociation. In the GLO-CAT complex, GLO-mediated H2O2 production during photorespiration is very high, whereas the affinity of CAT for H2O2 （measured Km ≈ 43 raM） is extraordinarily low. This unique combination can further potentiate the increase in H2O2 when GLO is dissociated from CAT. Taken together, we propose that the physical association-dissociation of GLO and CAT, in response to environmental stress or stimuli, seems to serve as a specific mechanism to modulate H2O2 levels in rice.展开更多
Seeds of Indian mustard （Brassicajuncea （L.） Czern. et Coss.） were exposed to 0, 50, 100 and 150 mmol/L NaCI for 8 h and seeds were sown in an earthen pot. These stressed seedlings were subsequently sprayed with 1...Seeds of Indian mustard （Brassicajuncea （L.） Czern. et Coss.） were exposed to 0, 50, 100 and 150 mmol/L NaCI for 8 h and seeds were sown in an earthen pot. These stressed seedlings were subsequently sprayed with 10μmol/L salicylic acid （SA） at 30 d and were sampled at 60 d to assess the changes in growth, photosynthesis and antioxidant enzymes. The seedlings raised from the seeds treated with NaCI had significantly reduced growth and the activities of carbonic anhydrase, nitrate reductase and photosynthesis, and the decrease was proportional to the increase in NaCI concentration. However, the antioxidant enzymes （catalase, peroxidase and superoxide dismutase） and proline content was enhanced in response to NaCI and/or SA treatment, where their interaction had an additive effect. Moreover, the toxic effects generated by the lower concentration of NaCI （50 mmol/L） were completely overcome by the application of SA. It was, therefore, concluded that SA ameliorated the stress generated by NaCl through the alleviated antioxidant system.展开更多
Plants have evolved complex mechanisms to defend themselves against pathogens. It has been shown that several defense responses are influenced by light, and the red/far-red light photoreceptor phytochromes （PHY） mod...Plants have evolved complex mechanisms to defend themselves against pathogens. It has been shown that several defense responses are influenced by light, and the red/far-red light photoreceptor phytochromes （PHY） modulate plant defense responses in Arabidopsis. Blue light receptor cryptochromes （CRY） work together with PHY to regulate many light-controlled responses, including photomorphogenesis, floral induction, and entrainment of the circadian clock. We report here that the Arabidopsis blue light photoreceptor CRY1 positively regulates inducible resistance to Pseudomonas syringae under continuous light conditions. By challenging plants with R syringae pv. tomato （Pst.） DC3000 carrying avrRpt2, we demonstrate that effector-triggered local resistance is down-regulated in the cry1 mutant, leading to more pathogen multiplication. In plants overexpressing CRY1 （CRYl-ovx）, however, local resistance is significantly up-regulated. We also show that systemic acquired resistance （SAR） is positively regulated by CRY1, and that salicylic acid （SA）-induced pathogenesis-related gene PR-1 expression is reduced in the cry1 mutant, but enhanced in CRYl-ovx plants. However, our results in- dicate that CRY1 only modestly influences SA accumulation and has no effect on hypersensitive cell death. These results suggest that CRY1 may positively regulate R protein-mediated resistance to P. syringae with increased PR gene expression.展开更多
According to the chemical design, electrorheological properties of supramolecular complex from β-cyclodextrin polymer (β -CDP) were discussed. Six supramolecular complexes of β-cyclodextrin polymer with substituted...According to the chemical design, electrorheological properties of supramolecular complex from β-cyclodextrin polymer (β -CDP) were discussed. Six supramolecular complexes of β-cyclodextrin polymer with substituted salicylic acid and 3-hydroxy-2-naphthoic acid were synthesized by the solid-phase self-assembly method, and their component and structure were characterized by NMR, FT-IR, UV-vis and the fluorescence analysis. Then the electrorheological properties of their suspensions in silicone oil were investigated under DC electric fields. It was found that the yield stresses of these supramolecular complex ER fluids were 7.3–9.8 kPa at 4 kV/mm in DC electric field, which were enhanced by 34%–72% compared with that of pure β-CDP. Among them, that of β-CDP/3-hydroxy-2-naphthoic acid ER fluid was the highest. It was also found that the ER effect of supramolecular complexes can be controlled by changing different guests. When the substituted group is at phenyl ring, ER behavior can be slightly adjusted by the different substituted groups, their number as well as their position at phenyl ring. This can be proved by the measurement of dielectric properties.展开更多
The transcription factor WRKY70 was previously reported to be a common component in salicylic acid （SA） and jasmonate （JA） mediated signal pathways in Arabidopsis. Here, we present that the inactivation of the WRK...The transcription factor WRKY70 was previously reported to be a common component in salicylic acid （SA） and jasmonate （JA） mediated signal pathways in Arabidopsis. Here, we present that the inactivation of the WRKY70 gene in wrky70-1 mutant does not alter the responses of both JA and SA, and that wrky70 mutation is unable to restore the coil mutant in JA responses. However, overexpression of WRKY70 reduces JA responses such as expression of JA-induced genes and JA-inhibitory root growth, and activates expression of SA-inducible PR1. These data indicate that the WRKY70 is important but not indispensable for JA and SA signaling, and that other regulators may display the redundant role with WRKY70 in modulation of JA and SA responses in Arabidopsis. Furthermore, we showed that JA inhibits expression of WRKY70 and PR1 by both COi1-dependent and COi1-independent pathways.展开更多
Soil salinity is one of the most important problems of crop production in estuarine and coastal zones. Improvement in salt tolerance of major food crops is an important way for the economic utilization of coastal zone...Soil salinity is one of the most important problems of crop production in estuarine and coastal zones. Improvement in salt tolerance of major food crops is an important way for the economic utilization of coastal zones. This study proved that the application of salicylic acid(SA) improved the growth and yield under salt stress conditions and investigated its physiological mechanisms for salt tolerance. The investigation on the effect of SA for salt tolerance during germination showed that the decreased rates of germination and growth(in terms of shoot and root lengths) by the salt stress were significantly increased by the SA application(SA + NaCl). The treatment of SA to the high and low saline soils enhanced the growth, yield and nutrient values of rice. The effects of SA on Na^+, K^+ and Cl~– ionic accumulation were traced under salt stress condition by inductively coupled plasma optical emission spectrometry and ion chromatography. It was revealed that the increased accumulation of Na^+ and Clˉ ions by the salt stress were reduced by SA application. An increased concentration of endogenous SA level was detected from the SA-treated rice varieties(ASD16 and BR26) by liquid chromatography electrospray Ionization-tandem mass spectrometry. The activities of antioxidant enzymes such as superoxide dismutase, catalase and peroxidase were increased by salt stress whereas decreased by the SA application. The study proved that the application of SA could alleviate the adverse effects of salt stress by the regulation of physiological mechanism in rice plants. In spite of salt stress, it can be applied to the coastal and estuarine regions to increase the rice production.展开更多
This paper focused on the effect of spraying chitosan and salicylic acid to Litchi under low temperature stress conditions.The physiology and biochemistry of litchi were studied as well.Results showed that the appropr...This paper focused on the effect of spraying chitosan and salicylic acid to Litchi under low temperature stress conditions.The physiology and biochemistry of litchi were studied as well.Results showed that the appropriate concentration of chitosan and salicylic acid treatment could effectively reduce injury caused by low temperature to litchi,compared with water control,chlorophyll,proline,soluble protein content of litchi after treatment and the activity of protective enzyme increasing significantly.However,the accumulation of resistance could significantly be improved.Furthermore,when 1 000 mg/L chitosan combined with 50 mg/L salicylic acid,the litchi acquired the best cold resistance capability.展开更多
Salicylic acid(SA)is an important phytohormone mediating both local and systemic defense responses in plants.Despite over half a century of research,how plants biosynthesize SA remains unresolved.In Arabidop-sis,a maj...Salicylic acid(SA)is an important phytohormone mediating both local and systemic defense responses in plants.Despite over half a century of research,how plants biosynthesize SA remains unresolved.In Arabidop-sis,a major part of SA is derived from isochorismate,a key intermediate produced by the isochorismate syn-thase,which is reminiscent of SA biosynthesis in bacteria.Whereas bacteria employ an isochorismate pyru-vate lyase(IPL)that catalyzes the turnover of isochorismate to pyruvate and SA,plants do not contain an IPL ortholog and generate SA from isochorismate through an unknown mechanism.Combining genetic and biochemical approaches,we delineated the SA biosynthetic pathway downstream of isochorismate in Ara-bidopsis.We found that PBS3,a GH3 acyl adenylase-family enzyme important for SA accumulation,catalyzes ATP-and Mg2+-dependent conjugation of L-glutamate primarily to the 8-carboxyl of isochorismate and yields the key SA biosynthetic intermediate,isochorismoyl-glutamate A.Moreover,we discovered that EPS1,a BAHD acyltransferase-family protein with a previously implicated role in SA accumulation upon pathogen attack,harbors a noncanonical active site and an unprecedented isochorismoyl-glutamate A pyruvoyl-glutamate lyase activity that produces SA from the isochorismoyl-glutamate A substrate.Together,PBS3 and EPS1 form a two-step metabolic pathway to produce SA from isochorismate in Arabidopsis,which is distinct from how SA is biosynthesized in bacteria.This study closes a major knowledge gap in plant SA meta-bolism and would help develop new strategies for engineering disease resistance in crop plants.展开更多
The Arabidopsis accelerated cell death 6-1 （acd6-1） mutant shows constitutive defense, cell death, and ex- treme dwarf phenotypes. In a screen for acd6-1 suppressors, we identified a mutant that was disrupted by a T...The Arabidopsis accelerated cell death 6-1 （acd6-1） mutant shows constitutive defense, cell death, and ex- treme dwarf phenotypes. In a screen for acd6-1 suppressors, we identified a mutant that was disrupted by a T-DNA in the PHOSPHATE TRANSPORTER 4;1 （PHT4;1） gene. The suppressor mutant pht4;1-1 is dominant, expresses truncated PHT4;1 transcripts, and is more susceptible to virulent Pseudomonas syringae strains but not to several avirulent strains. Treat- ment with a salicylic acid （SA） agonist induced a similar level of resistance in Col-0 and pht4;1-1, suggesting that PHT4;1 acts upstream of the SA pathway. Genetic analysis further indicates that PHT4,1 contributes to SID2-dependent and -in- dependent pathways. Transgenic expression of the DNA fragment containing the PHT4;1-1 region or the full-length PHT4;1 gene in wild-type conferred enhanced susceptibility to Pseudomonas infection. Interestingly, expression of PHT4;1 is reg- ulated by the circadian clock. Together, these data suggest that the phosphate transporter PHT4;1 is critical for basal defense and also implicate a potential role of the circadian clock in regulating innate immunity of Arabidopsis.展开更多
Glutaredoxins are small heat-stable oxidoreductases that transfer electrons from glutathione （GSH） to oxi- dized cysteine residues, thereby contributing to protein integrity and regulation. In Arabidopsis thaliana, ...Glutaredoxins are small heat-stable oxidoreductases that transfer electrons from glutathione （GSH） to oxi- dized cysteine residues, thereby contributing to protein integrity and regulation. In Arabidopsis thaliana, floral glutare- doxins ROXY1 and ROXY2 and pathogen-induced ROXY19/GRX480 interact with bZIP transcription factors of the TGACG （TGA） motif-binding family. ROXY1, ROXY2, and TGA factors PERIANTHIA, TGA9, and TGA10 play essential roles in floral development. In contrast, ectopically expressed ROXY19/GRX480 negatively regulates expression of jasmonic acid （JA）/ ethylene （ET）-induced defense genes through an unknown mechanism that requires clade II transcription factors TGA2, TGA5, and/or TGA6. Here, we report that at least 17 of the 21 land plant-specific glutaredoxins encoded in the Arabidopsis genome interact with TGA2 in a yeast-two-hybrid system. To investigate their capacity to interfere with the expression of JA/ET-induced genes, we developed a transient expression system. Activation of the ORA59 （OCTADECANOID-RESPONSIVE ARABIDOPSIS AP2/ERF-domain protein 59） promoter by transcription factor EIN3 （ETHYLENE INSENSITVE 3） was sup- pressed by co-expressed ROXY19/GRX480. Suppression depended on the L＊＊LL motif in the C-terminus of ROXY19/ GRX480. This putative protein interaction domain was recently described as being essential for the TGA/ROXY interaction. Ten of the 17 tested ROXY proteins suppressed ORA59 promoter activity, which correlated with the presence of the C-terminal ALWL motif, which is essential for ROXY1 function in flower development. ROXY19/GRX480-mediated repres- sion depended on the GSH binding site, suggesting that redox modification of either TGA factors or as yet unknown target proteins is important for the suppression of ORA59 promoter activity.展开更多
花药接种前麦穗置- 20 °C、10 m in 预处理有利于出愈和绿苗分化。花药接种后37 °C、8 h 培养使出愈率由8.2%(对照) 提高到29.0% 。在诱导培养基上附加2 m g/L的水杨酸 (SA) 对愈伤组织分化有促进作用, 而不影响出愈和绿苗分...花药接种前麦穗置- 20 °C、10 m in 预处理有利于出愈和绿苗分化。花药接种后37 °C、8 h 培养使出愈率由8.2%(对照) 提高到29.0% 。在诱导培养基上附加2 m g/L的水杨酸 (SA) 对愈伤组织分化有促进作用, 而不影响出愈和绿苗分化。诱导培养基上附加0.02 m g/L表-油菜素内酯 (epi-BR) 能使绿苗分化率由25.7% (对照) 提高到47.2% , 白苗分化率由31.4% 降低到24.3% , 当epi-BR浓度提高到0.2 m g/L时, 却对绿苗和白苗分化均表现抑制作用。展开更多
Kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson cv. Bruno) was used toinvestigate the effects of acetylsalicylic acid (ASA, 1.0 mmol/L, pH 3.5) and ethylene (100 mL/L) treat-ments on changes at...Kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson cv. Bruno) was used toinvestigate the effects of acetylsalicylic acid (ASA, 1.0 mmol/L, pH 3.5) and ethylene (100 mL/L) treat-ments on changes at endogenous salicylic acid (SA) levels and other senescence-related factors duringfruit ripening and softening at 20 ℃. The level of endogenous SA in ripening fruits declined and a closerelationship was observed between the change at endogenous SA level and the rate of fruit ripening andsoftening. ASA treatment elevated SA level in the fruit, slowed down the increases in lipoxygenase (LOX)and allene oxide synthase (AOS) activities, decreased the O22-. production in the preclimacteric phase andthe early phase of ethylene climacteric rise, maintained the stability of cell membrane, inhibited ethylenebiosynthesis, postponed the onset of the ethylene climacteric, and delayed the process of fruit ripeningand softening. On the contrary, application of ethylene to ripening kiwifruit resulted at a lower SA level, anaccelerated increases in the activities of LOX and AOS and the rate of O22-. production, an elevated relativeelectric conductivity and an advanced onset of ethylene climacteric, and a quicker fruit ripening andsoftening. It is suggested that the effects of ASA on ripening kiwifruit can be attributed to its ability toscavenge O22-. and/or to maintain stability of cell membrane.展开更多
文摘Jasmonates （JAs） are plant hormones with essential roles in plant defense and development. The basic- helix-loop-helix （bHLH） transcription factor （TF） MYC2 has recently emerged as a master regulator of most aspects of the jasmonate （JA） signaling pathway in Arabidopsis. MYC2 coordinates JA-mediated defense responses by antagonistically regulating two different branches of the JA signaling pathway that determine resistance to pests and pathogens, respectively. MYC2 is required for induced systemic resistance （ISR） triggered by beneficial soil microbes while MYC2 function is targeted by pathogens during effector-mediated suppression of innate immunity in roots. Another notable function of MYC2 is the regulation of crosstalk between the signaling pathways of JA and those of other phytohormones such as abscisic acid （ABA）, salicylic acid （SA）, gibberellins （GAs）, and auxin （IAA）. MYC2 also regulates interactions between JA signaling and light, phytochrome signaling, and the circadian clock, MYC2 is involved in JA-regulated plant development, lateral and adventitious root formation, flowering time, and shade avoidance syndrome. Related bHLH TFs MYC3 and MYC4 also regulate both overlapping and distinct MYC2-regulated functions in Arabidopsis while MYC2 orthologs act as ＇master switches＇ that regulate JA-mediated biosynthesis of secondary metabolites. Here, we briefly review recent studies that revealed mechanistic new insights into the mode of action of this versatile TF.
基金supported by a grant from the National Science Foundation (IOS-0842716) to Dr.Z Mou
文摘The small phenolic compound salicylic acid （SA） plays an important regulatory role in multiple physiological processes including plant im- mune response. Significant progress has been made during the past two decades in understanding the SA-mediated defense signaling network. Characterization of a number of genes functioning in SA biosynthesis, conjugation, accumulation, signaling, and crosstalk with other hormones such as jasmonic acid, ethylene, abscisic acid, auxin, gibberellic acid, cytokinin, brassinosteroid, and peptide hormones has sketched the finely tuned immune response network. Full understanding of the mech- anism of plant immunity will need to take advantage of fast developing genomics tools and bioinformatics techniques. However, elucidating genetic components involved in these pathways by conventional ge- netics, biochemistry, and molecular biology approaches will continue to be a major task of the community. High-throughput method for SA quantification holds the potential for isolating additional mutants related to SA-mediated defense signaling.
文摘Growth-defense tradeoffs are thought to occur in plants due to resource restrictions, which demand prior- itization towards either growth or defense, depending on external and internal factors. These tradeoffs have profound implications in agriculture and natural ecosystems, as both processes are vital for plant survival, reproduction, and, ulti- mately, plant fitness. While many of the molecular mechanisms underlying growth and defense tradeoffs remain to be elucidated, hormone crosstalk has emerged as a major player in regulating tradeoffs needed to achieve a balance. In this review, we cover recent advances in understanding growth-defense tradeoffs in plants as well as what is known regard- ing the underlying molecular mechanisms. Specifically, we address evidence supporting the growth-defense tradeoff concept, as well as known interactions between defense signaling and growth signaling. Understanding the molecular basis of these tradeoffs in plants should provide a foundation for the development of breeding strategies that optimize the growth-defense balance to maximize crop yield to meet rising global food and biofuel demands.
基金This project is funded by the National Natural Science Foundation of China （31070233, 31171157）, Shanghai Pujiang Talent Program （11PJ1400700）, and partly supported by the National Basic Research Program of China （973 Program, 2012CB910500）, all granted to J.X.L. ACKNOWLEDGMENTS We would also like thank Drs Yuhya Wakasa and Fumio Takaiwa for providing the OslREI transgenic rice seeds. No conflict of interest declared.
文摘Protein folding in the endoplasmic reticulum （ER） is a fundamental process in plant cells that is vulnerable to many environmental stresses. When unfolded or misfolded proteins accumulate in the ER, the well-conserved unfolded protein response （UPR） is initiated to mitigate the ER stress by enhancing the protein folding capability and/or accelerating the ER-associated protein degradation. Here, we report the conservation of the activation mechanism of OsbZIP74 （also known as OsbZIP50）, an important ER stress regulator in monocot plant rice （Oryza sativa L.）. Under normal conditions, OsbZIP74 mRNA encodes a basic leucine-zipper transcription factor with a putative transmembrane domain. When treating with ER stress-inducing agents such as tunicamycin and DTT, the conserved double stem-loop structures of OsbZIP74 mRNA are spliced out. Thereafter, the resulting new OsbZIP74 mRNA produces the nucleus-localized form of OsbZIP74 protein, eliminating the hydrophobic region. The activated form of OsbZIP74 has transcriptional activation activity in both yeast cells and Arabidopsis leaf protoplasts. The induction of OsbZIP74 splicing is much suppressed in the OsIRE1 knock- down rice plants, indicating the involvement of OslRE1 in OsbZIP74 splicing. We also demonstrate that the unconventional splicing of OsbZIP74 mRNA is associated with heat stress and salicylic acid, which is an important plant hormone in systemic acquired resistance against pathogen or parasite.
基金Project supported by the National Key Basic Research and Development Program (No. 2002CB410804) the National Natural Science Foundation of China (No. 30671255).
文摘Salicylic acid （SA） was an essential component of the plant resistance to pathogens and also plays an important role in mediating plant response to some abiotic stress. The possible effects of SA on the growth and H2O2-metabolizing enzymes in rice seedlings under lead stress were studied. When rice seedlings grown in nutrient solution containing Pb^2＋ （0, 0.05, 0.15, 0.25 mmol/L） for 18 d, the plant biomass as well as the chlorophyll content of leaves decreased with increasing Pb concentration. The pre-treatment with SA （treated with 0.1 mmol/L SA for 48 h before Pb stress） partially protected seedlings from Pb toxicity. The chlorophyll contents were significant higher in leaves of Pb-exposed with SA pre-treatment seedlings than in Pb-exposed plants at the same Pb intensity. SA pre-treated alone could significantly increase the length of shoot and root of seedlings but the vigour difference was not marked under long-term exposure to Pb toxicity. SA pre-treated influence the H2O2 level in leaves of seedlings by up-regulating the activity of superoxide dismutase （SOD）, repressing the activity of catalase （CAT） and ascorbate peroxidase （APX） depending on the concentrations of Pb^2＋ in the growth medium. The results supported the conclusion that SA played a positive role in rice seedlings against Pb toxicity.
文摘Old leaves of wild-type rice plants （Oryza sativa L. cv. Nipponbare） are more resistant to blast fungus （Magnaporthe grisea） than new leaves. In contrast, both old and new leaves of the rice phytochrome triple mutant （phyAphyBphyC） are susceptible to blast fungus. We demonstrate that pathogenesis-related class 1 （PR1） proteins are rapidly and strongly induced during M. grisea infection and following exogenous jasmonate （JA） or salicylic acid （SA） exposure in the old leaves, but not in the new leaves of the wild-type. In contrast, the accumulation of PR1 proteins was significantly attenuated in old and new leaves of the phyAphyBphyC mutant. These results suggest that phytochromes are required for the induction of PR1 proteins in rice. Basal transcription levels of PRla and PRlb were substantially higher in the wildtype as compared to the phyAphyBphyC mutant, suggesting that phytochromes also are required for basal expression of PR1 genes. Moreover, the transcript levels of genes known to function in SA- or JA-dependent defense pathways were regulated by leaf age and functional phytochromes. Taken together, our findings demonstrate that phytochromes are required in rice for age-related resistance to M. grisea and may indirectly increase PR1 gene expression by regulating SA- and JA-dependent defense pathways.
文摘The possible physiological mechanism of enhancement of cold tolerance by salicylic acid (SA) in banana seedlings ( Musa acuminata cv. Williams 8188) was explored. Measurements of leakage electrolyte after 2 d of recovery at 30/22 ℃ (day/night) following 3 d of cold stress at 7 ℃ showed that pretreatment with hydroponic solution containing SA 0.3-0.9 mmol/L as foliar spray under normal growth conditions (30/22 ℃) could significantly enhance cold tolerance of banana plants. The highest enhancing effect of SA occurred at 0.5 mmol/L and it showed the lowest leakage rate of electrolyte or smaller leaf wilting area after 2 d of recovery at normal temperature from 3 d of 7 ℃ or 5 ℃ cold stress. Higher concentrations (≥2.5 mmol/L) of SA, however, caused more electrolyte leakage, indicating that they aggravated chilling damage. Enhanced cold tolerance by SA could be related to H 2O 2 metabolism. Compared with water_treated seedlings (control), SA 0.5 mmol/L treatment inhibited activities of catalase (CAT) and ascorbate peroxidase (APX), increased peroxidase (POX) activity, but did not affect the activity of superoxide dismutase (SOD) under normal growth conditions, and these changes might lead to an accumulation of H 2O 2, whereas SA pretreatment enhanced the activities of CAT and APX, and reduced the increase in productions of H 2O 2 and thiobarbituric acid_reaction substances (TBARS) during subsequent 7 ℃ cold stress and recovery periods. Exogenous H 2O 2 treatments (1.5 -2.5 mmol/L) also increased cold tolerance of banana seedlings. Furthermore, pretreatment of banana seedlings with dimethylthiourea (a trap for H 2O 2) significantly inhibited cold tolerance induced by SA. These results suggested that endogenous H 2O 2 may be required for SA_enhanced cold tolerance. The significance of the interaction of SA, H 2O 2 and H 2O 2_metabolizing enzymes during cold stress has been discussed.
基金This work was supported by the National Natural Science Foundation of China （31170222, 31470343, U 1201212）.
文摘Rapid and dynamic change in hydrogen peroxide （H2O2） levels can serve as an important signal to regulate various biological processes in plants. The change is realized by tilting the balance between its production and scavenging rates, in which membrane-associated NADPH oxidases are known to play a crucial role. Functioning independently from NADPH oxidases, glycolate oxidase （GLO） was recently demonstrated as an aitemative source for H2O2 production during both germ-for-germ and non-host resistance in plants. In this study, we show that GLO physically interacts with catalase （CAT） in rice leaves, and that the interaction can be deregulated by salicylic acid （SA）. Furthermore, the GLO-mediated H2O2 accumulation is synergistically enhanced by SA. Based on the well-known mechanism of substrate channeling in enzyme complexes, SA-induced H2O2 accumulation likely results from SA-induced GLO-CAT dissociation. In the GLO-CAT complex, GLO-mediated H2O2 production during photorespiration is very high, whereas the affinity of CAT for H2O2 （measured Km ≈ 43 raM） is extraordinarily low. This unique combination can further potentiate the increase in H2O2 when GLO is dissociated from CAT. Taken together, we propose that the physical association-dissociation of GLO and CAT, in response to environmental stress or stimuli, seems to serve as a specific mechanism to modulate H2O2 levels in rice.
文摘Seeds of Indian mustard （Brassicajuncea （L.） Czern. et Coss.） were exposed to 0, 50, 100 and 150 mmol/L NaCI for 8 h and seeds were sown in an earthen pot. These stressed seedlings were subsequently sprayed with 10μmol/L salicylic acid （SA） at 30 d and were sampled at 60 d to assess the changes in growth, photosynthesis and antioxidant enzymes. The seedlings raised from the seeds treated with NaCI had significantly reduced growth and the activities of carbonic anhydrase, nitrate reductase and photosynthesis, and the decrease was proportional to the increase in NaCI concentration. However, the antioxidant enzymes （catalase, peroxidase and superoxide dismutase） and proline content was enhanced in response to NaCI and/or SA treatment, where their interaction had an additive effect. Moreover, the toxic effects generated by the lower concentration of NaCI （50 mmol/L） were completely overcome by the application of SA. It was, therefore, concluded that SA ameliorated the stress generated by NaCl through the alleviated antioxidant system.
文摘Plants have evolved complex mechanisms to defend themselves against pathogens. It has been shown that several defense responses are influenced by light, and the red/far-red light photoreceptor phytochromes （PHY） modulate plant defense responses in Arabidopsis. Blue light receptor cryptochromes （CRY） work together with PHY to regulate many light-controlled responses, including photomorphogenesis, floral induction, and entrainment of the circadian clock. We report here that the Arabidopsis blue light photoreceptor CRY1 positively regulates inducible resistance to Pseudomonas syringae under continuous light conditions. By challenging plants with R syringae pv. tomato （Pst.） DC3000 carrying avrRpt2, we demonstrate that effector-triggered local resistance is down-regulated in the cry1 mutant, leading to more pathogen multiplication. In plants overexpressing CRY1 （CRYl-ovx）, however, local resistance is significantly up-regulated. We also show that systemic acquired resistance （SAR） is positively regulated by CRY1, and that salicylic acid （SA）-induced pathogenesis-related gene PR-1 expression is reduced in the cry1 mutant, but enhanced in CRYl-ovx plants. However, our results in- dicate that CRY1 only modestly influences SA accumulation and has no effect on hypersensitive cell death. These results suggest that CRY1 may positively regulate R protein-mediated resistance to P. syringae with increased PR gene expression.
基金This work was supported by the National Namral Science Foundation of China(Grant No.59832090)the National Natural Science Foundation of China for Distinguished Young Scholar(Grant No.50025207)the'863'Foundation(Grant No.2001AA327130).
文摘According to the chemical design, electrorheological properties of supramolecular complex from β-cyclodextrin polymer (β -CDP) were discussed. Six supramolecular complexes of β-cyclodextrin polymer with substituted salicylic acid and 3-hydroxy-2-naphthoic acid were synthesized by the solid-phase self-assembly method, and their component and structure were characterized by NMR, FT-IR, UV-vis and the fluorescence analysis. Then the electrorheological properties of their suspensions in silicone oil were investigated under DC electric fields. It was found that the yield stresses of these supramolecular complex ER fluids were 7.3–9.8 kPa at 4 kV/mm in DC electric field, which were enhanced by 34%–72% compared with that of pure β-CDP. Among them, that of β-CDP/3-hydroxy-2-naphthoic acid ER fluid was the highest. It was also found that the ER effect of supramolecular complexes can be controlled by changing different guests. When the substituted group is at phenyl ring, ER behavior can be slightly adjusted by the different substituted groups, their number as well as their position at phenyl ring. This can be proved by the measurement of dielectric properties.
基金the National Natural Science Foundation of China (30630044,30671121,30770195 and 30771147).
文摘The transcription factor WRKY70 was previously reported to be a common component in salicylic acid （SA） and jasmonate （JA） mediated signal pathways in Arabidopsis. Here, we present that the inactivation of the WRKY70 gene in wrky70-1 mutant does not alter the responses of both JA and SA, and that wrky70 mutation is unable to restore the coil mutant in JA responses. However, overexpression of WRKY70 reduces JA responses such as expression of JA-induced genes and JA-inhibitory root growth, and activates expression of SA-inducible PR1. These data indicate that the WRKY70 is important but not indispensable for JA and SA signaling, and that other regulators may display the redundant role with WRKY70 in modulation of JA and SA responses in Arabidopsis. Furthermore, we showed that JA inhibits expression of WRKY70 and PR1 by both COi1-dependent and COi1-independent pathways.
文摘Soil salinity is one of the most important problems of crop production in estuarine and coastal zones. Improvement in salt tolerance of major food crops is an important way for the economic utilization of coastal zones. This study proved that the application of salicylic acid(SA) improved the growth and yield under salt stress conditions and investigated its physiological mechanisms for salt tolerance. The investigation on the effect of SA for salt tolerance during germination showed that the decreased rates of germination and growth(in terms of shoot and root lengths) by the salt stress were significantly increased by the SA application(SA + NaCl). The treatment of SA to the high and low saline soils enhanced the growth, yield and nutrient values of rice. The effects of SA on Na^+, K^+ and Cl~– ionic accumulation were traced under salt stress condition by inductively coupled plasma optical emission spectrometry and ion chromatography. It was revealed that the increased accumulation of Na^+ and Clˉ ions by the salt stress were reduced by SA application. An increased concentration of endogenous SA level was detected from the SA-treated rice varieties(ASD16 and BR26) by liquid chromatography electrospray Ionization-tandem mass spectrometry. The activities of antioxidant enzymes such as superoxide dismutase, catalase and peroxidase were increased by salt stress whereas decreased by the SA application. The study proved that the application of SA could alleviate the adverse effects of salt stress by the regulation of physiological mechanism in rice plants. In spite of salt stress, it can be applied to the coastal and estuarine regions to increase the rice production.
文摘This paper focused on the effect of spraying chitosan and salicylic acid to Litchi under low temperature stress conditions.The physiology and biochemistry of litchi were studied as well.Results showed that the appropriate concentration of chitosan and salicylic acid treatment could effectively reduce injury caused by low temperature to litchi,compared with water control,chlorophyll,proline,soluble protein content of litchi after treatment and the activity of protective enzyme increasing significantly.However,the accumulation of resistance could significantly be improved.Furthermore,when 1 000 mg/L chitosan combined with 50 mg/L salicylic acid,the litchi acquired the best cold resistance capability.
基金This work was supported by the Pew Scholar Program in the Biomedical Sciences,the Searle Scholars Program,and the National Science Foundation(CHE-1709616).
文摘Salicylic acid(SA)is an important phytohormone mediating both local and systemic defense responses in plants.Despite over half a century of research,how plants biosynthesize SA remains unresolved.In Arabidop-sis,a major part of SA is derived from isochorismate,a key intermediate produced by the isochorismate syn-thase,which is reminiscent of SA biosynthesis in bacteria.Whereas bacteria employ an isochorismate pyru-vate lyase(IPL)that catalyzes the turnover of isochorismate to pyruvate and SA,plants do not contain an IPL ortholog and generate SA from isochorismate through an unknown mechanism.Combining genetic and biochemical approaches,we delineated the SA biosynthetic pathway downstream of isochorismate in Ara-bidopsis.We found that PBS3,a GH3 acyl adenylase-family enzyme important for SA accumulation,catalyzes ATP-and Mg2+-dependent conjugation of L-glutamate primarily to the 8-carboxyl of isochorismate and yields the key SA biosynthetic intermediate,isochorismoyl-glutamate A.Moreover,we discovered that EPS1,a BAHD acyltransferase-family protein with a previously implicated role in SA accumulation upon pathogen attack,harbors a noncanonical active site and an unprecedented isochorismoyl-glutamate A pyruvoyl-glutamate lyase activity that produces SA from the isochorismoyl-glutamate A substrate.Together,PBS3 and EPS1 form a two-step metabolic pathway to produce SA from isochorismate in Arabidopsis,which is distinct from how SA is biosynthesized in bacteria.This study closes a major knowledge gap in plant SA meta-bolism and would help develop new strategies for engineering disease resistance in crop plants.
文摘The Arabidopsis accelerated cell death 6-1 （acd6-1） mutant shows constitutive defense, cell death, and ex- treme dwarf phenotypes. In a screen for acd6-1 suppressors, we identified a mutant that was disrupted by a T-DNA in the PHOSPHATE TRANSPORTER 4;1 （PHT4;1） gene. The suppressor mutant pht4;1-1 is dominant, expresses truncated PHT4;1 transcripts, and is more susceptible to virulent Pseudomonas syringae strains but not to several avirulent strains. Treat- ment with a salicylic acid （SA） agonist induced a similar level of resistance in Col-0 and pht4;1-1, suggesting that PHT4;1 acts upstream of the SA pathway. Genetic analysis further indicates that PHT4,1 contributes to SID2-dependent and -in- dependent pathways. Transgenic expression of the DNA fragment containing the PHT4;1-1 region or the full-length PHT4;1 gene in wild-type conferred enhanced susceptibility to Pseudomonas infection. Interestingly, expression of PHT4;1 is reg- ulated by the circadian clock. Together, these data suggest that the phosphate transporter PHT4;1 is critical for basal defense and also implicate a potential role of the circadian clock in regulating innate immunity of Arabidopsis.
文摘Glutaredoxins are small heat-stable oxidoreductases that transfer electrons from glutathione （GSH） to oxi- dized cysteine residues, thereby contributing to protein integrity and regulation. In Arabidopsis thaliana, floral glutare- doxins ROXY1 and ROXY2 and pathogen-induced ROXY19/GRX480 interact with bZIP transcription factors of the TGACG （TGA） motif-binding family. ROXY1, ROXY2, and TGA factors PERIANTHIA, TGA9, and TGA10 play essential roles in floral development. In contrast, ectopically expressed ROXY19/GRX480 negatively regulates expression of jasmonic acid （JA）/ ethylene （ET）-induced defense genes through an unknown mechanism that requires clade II transcription factors TGA2, TGA5, and/or TGA6. Here, we report that at least 17 of the 21 land plant-specific glutaredoxins encoded in the Arabidopsis genome interact with TGA2 in a yeast-two-hybrid system. To investigate their capacity to interfere with the expression of JA/ET-induced genes, we developed a transient expression system. Activation of the ORA59 （OCTADECANOID-RESPONSIVE ARABIDOPSIS AP2/ERF-domain protein 59） promoter by transcription factor EIN3 （ETHYLENE INSENSITVE 3） was sup- pressed by co-expressed ROXY19/GRX480. Suppression depended on the L＊＊LL motif in the C-terminus of ROXY19/ GRX480. This putative protein interaction domain was recently described as being essential for the TGA/ROXY interaction. Ten of the 17 tested ROXY proteins suppressed ORA59 promoter activity, which correlated with the presence of the C-terminal ALWL motif, which is essential for ROXY1 function in flower development. ROXY19/GRX480-mediated repres- sion depended on the GSH binding site, suggesting that redox modification of either TGA factors or as yet unknown target proteins is important for the suppression of ORA59 promoter activity.
文摘花药接种前麦穗置- 20 °C、10 m in 预处理有利于出愈和绿苗分化。花药接种后37 °C、8 h 培养使出愈率由8.2%(对照) 提高到29.0% 。在诱导培养基上附加2 m g/L的水杨酸 (SA) 对愈伤组织分化有促进作用, 而不影响出愈和绿苗分化。诱导培养基上附加0.02 m g/L表-油菜素内酯 (epi-BR) 能使绿苗分化率由25.7% (对照) 提高到47.2% , 白苗分化率由31.4% 降低到24.3% , 当epi-BR浓度提高到0.2 m g/L时, 却对绿苗和白苗分化均表现抑制作用。
文摘Kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson cv. Bruno) was used toinvestigate the effects of acetylsalicylic acid (ASA, 1.0 mmol/L, pH 3.5) and ethylene (100 mL/L) treat-ments on changes at endogenous salicylic acid (SA) levels and other senescence-related factors duringfruit ripening and softening at 20 ℃. The level of endogenous SA in ripening fruits declined and a closerelationship was observed between the change at endogenous SA level and the rate of fruit ripening andsoftening. ASA treatment elevated SA level in the fruit, slowed down the increases in lipoxygenase (LOX)and allene oxide synthase (AOS) activities, decreased the O22-. production in the preclimacteric phase andthe early phase of ethylene climacteric rise, maintained the stability of cell membrane, inhibited ethylenebiosynthesis, postponed the onset of the ethylene climacteric, and delayed the process of fruit ripeningand softening. On the contrary, application of ethylene to ripening kiwifruit resulted at a lower SA level, anaccelerated increases in the activities of LOX and AOS and the rate of O22-. production, an elevated relativeelectric conductivity and an advanced onset of ethylene climacteric, and a quicker fruit ripening andsoftening. It is suggested that the effects of ASA on ripening kiwifruit can be attributed to its ability toscavenge O22-. and/or to maintain stability of cell membrane.
