ABSTRACT Plant hormones have been extensively studied for their importance in innate immunity particularly in the dicotyledonous model plant Arabidopsis thaliana. However, only in the last decade, plant hormones were ...ABSTRACT Plant hormones have been extensively studied for their importance in innate immunity particularly in the dicotyledonous model plant Arabidopsis thaliana. However, only in the last decade, plant hormones were demonstrated to play conserved and divergent roles in fine-tuning immune responses in rice （Oryza sativa L.）, a monocotyledonous model crop plant. Emerging evidence showed that salicylic acid （SA） plays a role in rice basal defense but is differentially required by rice pattern recognition receptor （PRR） and resistance （R） protein-mediated immunity, and its function is likely dependent on the signaling pathway rather than the change of endogenous levels. Jasmonate （JA） plays an important role in rice basal defense against bacterial and fungal infection and may be involved in the SA-mediated resistance. Ethylene （ET） can act as a positive or negative modulator of disease resistance, depending on the pathogen type and environmental conditions. Brassinosteroid （BR） signaling and abscisic acid （ABA） either promote or defend against infection of pathogens with distinct infection/colonization strategies. Auxin and gibberellin （GA） are generally thought of as negative regulators of innate immunity in rice. Moreover, GA interacts antagonistically with JA signaling in rice development and immunity through the DELLA protein as a master regulator of the two hormone pathways. In this review, we summarize the roles of plant hormones in rice immunity and discuss their interplay/crosstalk mechanisms and the complex regulatory network of plant hormone pathways in fine-tuning rice immunity and growth.展开更多
Jasmonates （JAs） orchestrate immune responses upon wound/herbivore injury or infection by necrotro- phic pathogens. Elucidation of catabolic routes has revealed new complexity in jasmonate metabolism. Two integrated...Jasmonates （JAs） orchestrate immune responses upon wound/herbivore injury or infection by necrotro- phic pathogens. Elucidation of catabolic routes has revealed new complexity in jasmonate metabolism. Two integrated pathways attenuate signaling by turning over the active hormone jasmonoyl-isoleucine （JA-Ile） through w-oxidation or deconjugation, and define an indirect route forming the derivative 12OH-JA. Here, we provide evidence for a second 12OH-JA formation pathway by direct jasmonic acid （JA） oxidation. Three jasmonic acid oxidases （JAOs） of the 2-oxoglutarate dioxygenase family catalyze spe- cific oxidation of JA to 12OH-JA, and their genes are induced by wounding or infection by the fungus Botrytis cinerea. JA02 exhibits the highest basal expression, and its deficiency in jao2 mutants strongly enhanced antifungal resistance. The resistance phenotype resulted from constitutive expression of antimi- crobial markers rather than from their higher induction in infected jao2 plants and could be reversed by ectopic expression of any of the three JAOs injao2. Elevated defense injao2 was dependent on the activity of JASMONATE RESPONSE 1 （JAR1） and CORONATINE-INSENSITIVE 1 （COI1） but was not correlated with erihanced JA-Ile accumulation. Instead, jao2 mutant lines displayed altered accumulation of several JA species in healthy and challenged plants, suggesting elevated metabolic flux through JA-Ile. Collectively, these data identify the missing enzymes hydroxylating JA and uncover an important metabolic diversion mechanism for repressing basal JA defense responses.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
Biotic and abiotic stresses impose a serious limitation on crop productivity worldwide. Prior or simultaneous exposure to one type of stress often affects the plant response to other stresses, indicating extensive ove...Biotic and abiotic stresses impose a serious limitation on crop productivity worldwide. Prior or simultaneous exposure to one type of stress often affects the plant response to other stresses, indicating extensive overlap and cross-talk between stress-response signaling pathways. Systems biology approaches that integrate large genomic and prot-eomic data sets have facilitated identification of candidate genes that govern this stress-regulatory crosstalk. Recently, we constructed a yeast two-hybrid map around three rice proteins that control the response to biotic and abiotic stresses, namely the immune receptor XA21, which confers resistance to the Gram-negative bacterium, Xanthomonas oryzae pv. oryzae; NH1, the rice ortholog of NPR1, a key regulator of systemic acquired resistance; and the ethylene-responsive transcription factor, SUBIA, which confers tolerance to submergence stress. These studies coupled with transcriptional profiling and co-expression analyses identified a suite of proteins that are positioned at the interface of biotic and abiotic stress responses, including mitogen-activated protein kinase 5 （OsMPK5）, wall-associated kinase 25 （WAK25）, sucrose non-fermenting-l-related protein kinase-1 （SnRK1）, SUBIA binding protein 23 （SAB23）, and several WRKY family tran- scription factors. Emerging evidence suggests that these genes orchestrate crosstalk between biotic and abiotic stresses through a variety of mechanisms, including regulation of cellular energy homeostasis and modification of synergistic and/or antagonistic interactions between the stress hormones salicylic acid, ethylene, jasmonic acid, and abscisic acid.展开更多
为了探讨丛枝菌根(arbuscular mycorrhizal,AM)真菌对西瓜耐盐性的影响,以西瓜[Citrullus lanatus(Thunb.)Matsum et Nakai]品种‘京欣四号’为材料,研究了AM真菌对盐胁迫下西瓜幼苗叶片防御酶活性、脯氨酸及内源激素含量的影响。本试验...为了探讨丛枝菌根(arbuscular mycorrhizal,AM)真菌对西瓜耐盐性的影响,以西瓜[Citrullus lanatus(Thunb.)Matsum et Nakai]品种‘京欣四号’为材料,研究了AM真菌对盐胁迫下西瓜幼苗叶片防御酶活性、脯氨酸及内源激素含量的影响。本试验共4个处理:对照(未盐胁迫且不接种AM真菌)、只进行盐胁迫、只接种AM真菌、盐胁迫且接种AM真菌。结果表明:盐胁迫下,接种AM真菌提高了西瓜幼苗叶片抗氧化系统中的超氧化物歧化酶和过氧化氢酶的活性,比未接种的处理提高了17.3%和5.4%;并增加叶片中脯氨酸、赤霉素和吲哚乙酸的含量,分别比对照增加了44.2%、22.9%和21.9%。结论认为接种AM真菌能够增强西瓜幼苗对盐胁迫的抗性。展开更多
Chinese cabbage(Brassica rapa subsp.pekinensis)suffers from soft rot disease caused by Pectobacterium carotovorum(Pc).To uncover the mechanisms underlying the defense response of Chinese cabbage to Pc,we constructed a...Chinese cabbage(Brassica rapa subsp.pekinensis)suffers from soft rot disease caused by Pectobacterium carotovorum(Pc).To uncover the mechanisms underlying the defense response of Chinese cabbage to Pc,we constructed a suppression subtractive hybridization(SSH)library from Pc-infected cabbage and obtained 1919 non-redundant expressed sequence tags(ESTs),which were used for cDNA microarray.We detected 800 differentially expressed genes(DEGs)in cabbage at different time points post-Pc inoculation,which were further confirmed by quantitative real-time PCR.One quarter of these DEGs were involved in the biotic stress pathways visualized by MapMan.Among them,8,8,1,3,and 2 DEGs were related to jasmonic acid(JA),ethylene(ET),JA+ET,auxin,and abscisic acid(ABA)signaling pathways,respectively,while no DEG was detected for salicylic acid(SA)signaling.Assessment of phytohormone production in the Pc-infected leaves showed that JA and ET production was increased,while SA production was decreased.Treatment with JA,methyl jasmonate(MeJA),the ET precursor 1-aminocyclopropane-1-carboxylate(ACC),or combinations thereof,reduced the disease severity,and the JA and JA+ACC treatments were superior and performed equally well.Our findings suggest that JA and ET may act synergistically against Pc infection in Chinese cabbage,and JA-mediated signaling might be the most significant.展开更多
PHYTOCHROME-INTERACTING FACTORs （PIFs） are members of the basic helix-loop-helix （bHLH） family of transcription factors in Arabidopsis. Since their discovery in phytochrome-mediated light signaling pathways, recen...PHYTOCHROME-INTERACTING FACTORs （PIFs） are members of the basic helix-loop-helix （bHLH） family of transcription factors in Arabidopsis. Since their discovery in phytochrome-mediated light signaling pathways, recent studies have unraveled new functions of PIFs in integrating multiple signaling pathways not only through their role as transcription factors directly targeting gene expression but also by interacting with diverse groups of factors to optimize plant growth and development. These include endogenous （e.g., hormonal） as well as abiotic （light, circadian, and elevated temperature） and biotic （defense responses） pathways. PIFs interact with key factors in each of these pathways and tailor the outcome of the signal integration among these pathways. This review discusses the roles of PIFs as pivotal signal integrators in regulating plant growth and development.展开更多
基金This work was supported by National Key Basic Research and Development Program Grant 2011 CB100700 （to Z.H.） Natural Science Foundation of China Grants 91117018 and 30730064 （to Z.H.）and US Department of Agriculture National Research Initiative Grant 2003-35319-17873 （to Y.Y.）. No conflict of interest declared.
文摘ABSTRACT Plant hormones have been extensively studied for their importance in innate immunity particularly in the dicotyledonous model plant Arabidopsis thaliana. However, only in the last decade, plant hormones were demonstrated to play conserved and divergent roles in fine-tuning immune responses in rice （Oryza sativa L.）, a monocotyledonous model crop plant. Emerging evidence showed that salicylic acid （SA） plays a role in rice basal defense but is differentially required by rice pattern recognition receptor （PRR） and resistance （R） protein-mediated immunity, and its function is likely dependent on the signaling pathway rather than the change of endogenous levels. Jasmonate （JA） plays an important role in rice basal defense against bacterial and fungal infection and may be involved in the SA-mediated resistance. Ethylene （ET） can act as a positive or negative modulator of disease resistance, depending on the pathogen type and environmental conditions. Brassinosteroid （BR） signaling and abscisic acid （ABA） either promote or defend against infection of pathogens with distinct infection/colonization strategies. Auxin and gibberellin （GA） are generally thought of as negative regulators of innate immunity in rice. Moreover, GA interacts antagonistically with JA signaling in rice development and immunity through the DELLA protein as a master regulator of the two hormone pathways. In this review, we summarize the roles of plant hormones in rice immunity and discuss their interplay/crosstalk mechanisms and the complex regulatory network of plant hormone pathways in fine-tuning rice immunity and growth.
文摘Jasmonates （JAs） orchestrate immune responses upon wound/herbivore injury or infection by necrotro- phic pathogens. Elucidation of catabolic routes has revealed new complexity in jasmonate metabolism. Two integrated pathways attenuate signaling by turning over the active hormone jasmonoyl-isoleucine （JA-Ile） through w-oxidation or deconjugation, and define an indirect route forming the derivative 12OH-JA. Here, we provide evidence for a second 12OH-JA formation pathway by direct jasmonic acid （JA） oxidation. Three jasmonic acid oxidases （JAOs） of the 2-oxoglutarate dioxygenase family catalyze spe- cific oxidation of JA to 12OH-JA, and their genes are induced by wounding or infection by the fungus Botrytis cinerea. JA02 exhibits the highest basal expression, and its deficiency in jao2 mutants strongly enhanced antifungal resistance. The resistance phenotype resulted from constitutive expression of antimi- crobial markers rather than from their higher induction in infected jao2 plants and could be reversed by ectopic expression of any of the three JAOs injao2. Elevated defense injao2 was dependent on the activity of JASMONATE RESPONSE 1 （JAR1） and CORONATINE-INSENSITIVE 1 （COI1） but was not correlated with erihanced JA-Ile accumulation. Instead, jao2 mutant lines displayed altered accumulation of several JA species in healthy and challenged plants, suggesting elevated metabolic flux through JA-Ile. Collectively, these data identify the missing enzymes hydroxylating JA and uncover an important metabolic diversion mechanism for repressing basal JA defense responses.
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Biotic and abiotic stresses impose a serious limitation on crop productivity worldwide. Prior or simultaneous exposure to one type of stress often affects the plant response to other stresses, indicating extensive overlap and cross-talk between stress-response signaling pathways. Systems biology approaches that integrate large genomic and prot-eomic data sets have facilitated identification of candidate genes that govern this stress-regulatory crosstalk. Recently, we constructed a yeast two-hybrid map around three rice proteins that control the response to biotic and abiotic stresses, namely the immune receptor XA21, which confers resistance to the Gram-negative bacterium, Xanthomonas oryzae pv. oryzae; NH1, the rice ortholog of NPR1, a key regulator of systemic acquired resistance; and the ethylene-responsive transcription factor, SUBIA, which confers tolerance to submergence stress. These studies coupled with transcriptional profiling and co-expression analyses identified a suite of proteins that are positioned at the interface of biotic and abiotic stress responses, including mitogen-activated protein kinase 5 （OsMPK5）, wall-associated kinase 25 （WAK25）, sucrose non-fermenting-l-related protein kinase-1 （SnRK1）, SUBIA binding protein 23 （SAB23）, and several WRKY family tran- scription factors. Emerging evidence suggests that these genes orchestrate crosstalk between biotic and abiotic stresses through a variety of mechanisms, including regulation of cellular energy homeostasis and modification of synergistic and/or antagonistic interactions between the stress hormones salicylic acid, ethylene, jasmonic acid, and abscisic acid.
文摘为了探讨丛枝菌根(arbuscular mycorrhizal,AM)真菌对西瓜耐盐性的影响,以西瓜[Citrullus lanatus(Thunb.)Matsum et Nakai]品种‘京欣四号’为材料,研究了AM真菌对盐胁迫下西瓜幼苗叶片防御酶活性、脯氨酸及内源激素含量的影响。本试验共4个处理:对照(未盐胁迫且不接种AM真菌)、只进行盐胁迫、只接种AM真菌、盐胁迫且接种AM真菌。结果表明:盐胁迫下,接种AM真菌提高了西瓜幼苗叶片抗氧化系统中的超氧化物歧化酶和过氧化氢酶的活性,比未接种的处理提高了17.3%和5.4%;并增加叶片中脯氨酸、赤霉素和吲哚乙酸的含量,分别比对照增加了44.2%、22.9%和21.9%。结论认为接种AM真菌能够增强西瓜幼苗对盐胁迫的抗性。
基金the Beijing Leafy Vegetables Innovation Team of Modern Agro-industry Technology Research System,China(BAIC07)the Beijing Natural Science Foundation,China(5051002)。
文摘Chinese cabbage(Brassica rapa subsp.pekinensis)suffers from soft rot disease caused by Pectobacterium carotovorum(Pc).To uncover the mechanisms underlying the defense response of Chinese cabbage to Pc,we constructed a suppression subtractive hybridization(SSH)library from Pc-infected cabbage and obtained 1919 non-redundant expressed sequence tags(ESTs),which were used for cDNA microarray.We detected 800 differentially expressed genes(DEGs)in cabbage at different time points post-Pc inoculation,which were further confirmed by quantitative real-time PCR.One quarter of these DEGs were involved in the biotic stress pathways visualized by MapMan.Among them,8,8,1,3,and 2 DEGs were related to jasmonic acid(JA),ethylene(ET),JA+ET,auxin,and abscisic acid(ABA)signaling pathways,respectively,while no DEG was detected for salicylic acid(SA)signaling.Assessment of phytohormone production in the Pc-infected leaves showed that JA and ET production was increased,while SA production was decreased.Treatment with JA,methyl jasmonate(MeJA),the ET precursor 1-aminocyclopropane-1-carboxylate(ACC),or combinations thereof,reduced the disease severity,and the JA and JA+ACC treatments were superior and performed equally well.Our findings suggest that JA and ET may act synergistically against Pc infection in Chinese cabbage,and JA-mediated signaling might be the most significant.
基金We acknowledge support by grants from the National Institutes of Health （1R01 GM-114297）, National Science Foundation （MCB- 1543813）, U.S.-Israel Binationat Science Foundation （BSF#2015316） to E.H., and Rural Development Administration, Republic of Korea （P J01104001） to J.-I.K.
文摘PHYTOCHROME-INTERACTING FACTORs （PIFs） are members of the basic helix-loop-helix （bHLH） family of transcription factors in Arabidopsis. Since their discovery in phytochrome-mediated light signaling pathways, recent studies have unraveled new functions of PIFs in integrating multiple signaling pathways not only through their role as transcription factors directly targeting gene expression but also by interacting with diverse groups of factors to optimize plant growth and development. These include endogenous （e.g., hormonal） as well as abiotic （light, circadian, and elevated temperature） and biotic （defense responses） pathways. PIFs interact with key factors in each of these pathways and tailor the outcome of the signal integration among these pathways. This review discusses the roles of PIFs as pivotal signal integrators in regulating plant growth and development.
