The plant hormone auxin plays a critical role in regulating plant growth and development. Recent advances have been made in the understanding of auxin response pathways, primarily by the characterization of auxin resp...The plant hormone auxin plays a critical role in regulating plant growth and development. Recent advances have been made in the understanding of auxin response pathways, primarily by the characterization of auxin response mutants in Arabidopsis. In addition, microRNAs （miRNAs） have been shown to be critical regulators of genes important for normal plant development and physiology. However, little is known about possible interactions between miRNAs and hormonal signaling during normal development. Here we show that an Arabidopsis microRNA, miR167, which has a complementary sequence to a portion of the A UXINRESPONSE FACTOR6 （ARF6） and ARF8 mRNAs, can cause transcript degradation for ARF8, but not for ARF6. We report phenotypic characterizations of 35S：：MIR167b transgenic lines, and show that severe 35S：：MIR167b transgenic lines had phenotypes similar to those of an arf6 arf8 double mutant. The transgenic phenotypes suggest that miR167 may repress ARF6 at the level of translation. We demonstrate that the transgenic plants are defective in all four whods of floral organs. In the transgenic flowers, filaments were abnormally short, anthers could not properly release pollen, and pollen grains did not germinate. Our results provide an important link between the miRNA-mediated regulatory pathway of gene expression and the auxin signaling network promoting plant reproductive development.展开更多
Auxin,one of the first identified and most widely studied phytohormones,has been and will remain a hot topic in plant biology.After more than a century of passionate exploration,the mysteries of its synthesis,transpor...Auxin,one of the first identified and most widely studied phytohormones,has been and will remain a hot topic in plant biology.After more than a century of passionate exploration,the mysteries of its synthesis,transport,signaling,and metabolism have largely been unlocked.Due to the rapid development of new technologies,new methods,and new genetic materials,the study of auxin has entered the fast lane over the past 30 years.Here,we highlight advances in understanding auxin signaling,including auxin perception,rapid auxin responses,TRANSPORT INHIBITOR RESPONSE 1 and AUXIN SIGNALING F-boxes(TIR1/AFBs)-mediated transcriptional and non-transcriptional branches,and the epigenetic regulation of auxin signaling.We also focus on feedback inhibition mechanisms that prevent the over-amplification of auxin signals.In addition,we cover the TRANSMEMBRANE KINASE-mediated non-canonical signaling,which converges with TIR1/AFBs-mediated transcriptional regulation to coordinate plant growth and development.The identification of additional auxin signaling components and their regulation will continue to open new avenues of research in this field,leading to an increasingly deeper,more comprehensive understanding of how auxin signals are interpreted at the cellular level to regulate plant growth and development.展开更多
The changes in external K^＋ concentration affect plant root growth. However, the molecular mechanism for perceiving a K^＋ signal to modulate root growth remains unknown. It is hypothesized that the K^＋ channel AKTI...The changes in external K^＋ concentration affect plant root growth. However, the molecular mechanism for perceiving a K^＋ signal to modulate root growth remains unknown. It is hypothesized that the K^＋ channel AKTI is involved in low K^＋ sensing in the Arabidopsis root and subsequent regulation of root growth. Along with the decline of external K^＋ concentration, the primary root growth of wild-type plants was gradually inhibited. However, the primary root of the akt1 mutant could still grow under low K^＋（LK） conditions. Application of NAA inhibited akt1 root growth, but promoted wild-type root growth under LK conditions. By using the ProDR5：GFP and ProPIN1：PIN1-GFP lines, we found that LK treatment reduced auxin accumulation in wild-type root tips by degrading PIN1 proteins, which did not occur in the akt1 mutant. The LK-induced PIN1 degradation may be due to the inhibition of vesicle trafficking of PIN1 proteins. In conclusion, our findings indicate that AKT1 is required for an Arabidopsis response to changes in external K^＋, and subsequent regulation of K^＋-dependent root growth by modulating PINt degradation and auxin redistribution in the root.展开更多
Auxin is a crucial phytohormone that has various effects on the regulators of plant growth and development.Auxin signal transduction is mainly controlled by two gene families:auxin response factor(ARF)and auxin/indole...Auxin is a crucial phytohormone that has various effects on the regulators of plant growth and development.Auxin signal transduction is mainly controlled by two gene families:auxin response factor(ARF)and auxin/indole-3-acetic acid(Aux/IAA).ARFs are plant-specific transcription factors that bind directly to auxin response elements in the promoters of auxinresponsive genes.ARF proteins contain three conserved regions:a conserved N-terminal B3DNA-binding domain,a variable intermediate middle region domain that functions in activation or repression,and a C-terminal domain including the Phox and Bem1p region for dimerization,similar to theⅢandⅣelements of Aux/IAA,which facilitate protein–protein interaction through homodimerization of ARF proteins or heterodimerization of ARF and Aux/IAA proteins.In the two decades following the identification of the first ARF,23 ARF members have been identified and characterized in Arabidopsis.Using whole-genome sequencing,22,25,23,25,and 36 ARF genes have been identified in tomato,rice,wheat,sorghum,and maize,respectively,in addition to which the related biofunctions of some ARFs have been reported.ARFs play crucial roles in regulating the growth and development of roots,leaves,flowers,fruits,seeds,responses to biotic and abiotic stresses,and phytohormone signal crosstalk.In this review,we summarize the research progress on the structures and functions of ARFs in Arabidopsis,tomato,and cereal crops,to provide clues for future basic research on phytohormone signaling and the molecular design breeding of crops.展开更多
Overexpression of membrane steroid binding protein 1 （MSBP1） stimulates the root gravitropism and antigravitropism of hypocotyl, which is mainly due to the enhanced auxin redistribution in the bending regions of hyp...Overexpression of membrane steroid binding protein 1 （MSBP1） stimulates the root gravitropism and antigravitropism of hypocotyl, which is mainly due to the enhanced auxin redistribution in the bending regions of hypocotyls and root tips. The inhibitory effects by 1-N-naphthylphthalamic acid （NPA）, an inhibitor of polar auxin transport, are suppressed under the MSBP1 overexpression, suggesting the positive effects of MSBP1 on polar auxin transport. Interestingly, sub-cellular localization studies showed that MSBP1 is also localized in endosomes and observations of the membraneselective dye FM4-64 revealed the enhanced vesicle trafficking under MSBP1 overexpression. MSBPl-overexpressing seedlings are less sensitive to brefeldin A （BFA） treatment, whereas the vesicle trafficking was evidently reduced by suppressed MSBP1 expression. Enhanced MSBP1 does not affect the polar localization of PIN2, but stimulates the PIN2 cycling and enhances the asymmetric PIN2 redistribution under gravi-stimulation. These results suggest that MSBP1 could enhance the cycling of PIN2-containing vesicles to stimulate the auxin redistribution under gravi-stimulation, providing informative hints on interactions between auxin and steroid binding protein.展开更多
Tiller angle is a key agricultural trait that establishes plant architecture,which in turn strongly affects grain yield by influencing planting density in rice.The shoot gravity response plays a crucial role in the re...Tiller angle is a key agricultural trait that establishes plant architecture,which in turn strongly affects grain yield by influencing planting density in rice.The shoot gravity response plays a crucial role in the regulation of tiller angle in rice,but the underlying molecular mechanism is largely unknown.Here,we report the identification of the BIG TILLER ANGLE2(BTA2),which regulates tiller angle by controlling the shoot gravity response in rice.Loss-of-function mutation of BTA2 dramatically reduced auxin content and affected auxin distribution in rice shoot base,leading to impaired gravitropism and therefore a big tiller angle.BTA2 interacted with AUXIN RESPONSE FACTOR7(ARF7)to modulate rice tiller angle through the gravity signaling pathway.The BTA2 protein was highly conserved during evolution.Sequence variation in the BTA2 promoter of indica cultivars harboring a less expressed BTA2 allele caused lower BTA2 expression in shoot base and thus wide tiller angle during rice domestication.Overexpression of BTA2 significantly increased grain yield in the elite rice cultivar Huanghuazhan under appropriate dense planting conditions.Our findings thus uncovered the BTA2-ARF7 module that regulates tiller angle by mediating the shoot gravity response.Our work offers a target for genetic manipulation of plant architecture and valuable information for crop improvement by producing the ideal plant type.展开更多
Auxin plays critical roles in root formation and development. The components involved in this process, however, are not well understood. Here, we newly identified a peptide encoding gene, auxin-responsive endogenous p...Auxin plays critical roles in root formation and development. The components involved in this process, however, are not well understood. Here, we newly identified a peptide encoding gene, auxin-responsive endogenous polypeptide 1 （AREP1）, which is induced by auxin, and mediates root development in Arabidopsis. Expression of AREP1 was specific to the cotyledon and to root and shoot meristem tissues. Amounts of AREP1 transcripts and AREP1-green fluorescent protein fusion proteins were elevated in response to indoleacetic acid treatment. Suppression of AREP1 through RNAi silencing resulted in reduction of primary root length, increase of lateral root number, and expansion of adventitious roots, compared to the observations in wild-type plants in the presence of auxin. By contrast, transgenic plants overexpressing AREP1 showed enhanced growth of the primary root under auxin treatment. Additionally, rootmorphology, including lateral root number and adventitious roots, differed greatly between transgenic and wildtype plants. Further analysis indicated that the expression of auxin-responsive genes, such as IAA3, IAA7, IAA17, GH3.2, GH3.3, and SAUR-AC1, was significantly higher in AREP1 RNAi plants, and was slightly lower in AREP1 overexpressing plants than in wildtype plants. These results suggest that the novel endogenous peptide AREP1 plays an important role in the process of auxinmediated root development.展开更多
Plant growth regulators are biologically active signaling molecules that regulate a number of plant physiological processes. Auxin(indole-3-acetic acid) is an important plant growth regulator and is synthesized within...Plant growth regulators are biologically active signaling molecules that regulate a number of plant physiological processes. Auxin(indole-3-acetic acid) is an important plant growth regulator and is synthesized within plant tissues through L-tryptophan(L-TRP)-dependent and-independent pathways. It has been found that plants respond to exogenously applied L-TRP due to insufficient endogenous auxin biosynthesis. The exogenous application of L-TRP is highly significant for normal plant growth and development.L-tryptophan is applied through foliar spray, seed priming, and soil application. Soil-applied L-TRP is either directly taken up by plants or metabolized to auxin by soil microbiota and then absorbed by plant roots. Similarly, foliar spray and seed priming with L-TRP stimulates auxin synthesis within plants and improves the growth and productivity of agricultural crops. Furthermore, L-TRP contains approximately 14% nitrogen(N) in its composition, which is released upon its metabolism within a plant or in the rhizosphere and plays a role in enhancing crop productivity. This review deals with assessing crop responses under the exogenous application of L-TRP in normal and stressed environments, mode of action of L-TRP, advantages of using L-TRP over other auxin precursors, and role of the simultaneous use of L-TRP and auxin-producing microbes in improving the productivity of agricultural crops. To the best of our knowledge, this is the first review reporting the importance of the use of L-TRP in agriculture.展开更多
Light is an environmental signaling,whereas Aux/IAA proteins and Auxin Response Factors(ARFs)are regulators of auxin signalling.Aux/IAA proteins are unstable,and their degradation dependents on 26S ubiquitin-proteasom...Light is an environmental signaling,whereas Aux/IAA proteins and Auxin Response Factors(ARFs)are regulators of auxin signalling.Aux/IAA proteins are unstable,and their degradation dependents on 26S ubiquitin-proteasome and is promoted by Auxin.Auxin binds directly to a SCF-type ubiquitin-protein ligase,TIR1,facilitates the interaction between Aux/IAA proteins and TIR1,and then the degradation of Aux/IAA proteins.A few studies have reported that some ARFs are also unstable proteins,and their degradation is also mediated by 26S proteasome.In this study,by using of antibodies recognizing endogenous ARF7 proteins,we found that protein stability of ARF7 was affected by light.By expressing MYC tagged ARF activators in protoplasts,we found that degradation of ARF7 was inhibited by 26 proteasome inhibitors.In addition,at least ARF5 and ARF19 were also unstable proteins,and degradation of ARF5 via 26S proteasome was further confirmed by using stable transformed plants overexpressing ARF5 with a GUS tag.展开更多
Members of the ADP-ribosylation factor family,which are GTP-binding proteins, are involved in metabolite transport, cell division, and expansion.Although there has been a significant amount of research on small GTP-bi...Members of the ADP-ribosylation factor family,which are GTP-binding proteins, are involved in metabolite transport, cell division, and expansion.Although there has been a significant amount of research on small GTP-binding proteins, their roles and functions in regulating maize kernel size remain elusive. Here, we identified Zm Arf2 as a maize ADPribosylation factor-like family member that is highly conserved during evolution. Maize zmarf2 mutants showed a characteristic smaller kernel size. Conversely, ZmArf2 overexpression increased maize kernel size. Furthermore, heterologous expression of Zm Arf2 dramatically elevated Arabidopsis and yeast growth by promoting cell division. Using expression quantitative trait loci(e QTL) analysis, we determined that Zm Arf2 expression levels in various lines were mainly associated with variation at the gene locus. The promoters of Zm Arf2 genes could be divided into two types, p S and p L, that were significantly associated with both Zm Arf2 expression levels and kernel size. In yeast-one-hybrid screening, maize Auxin Response Factor 24(ARF24) is directly bound to the Zm Arf2 promoter region and negatively regulated Zm Arf2 expression.Notably, the p S and p L promoter types each contained an ARF24 binding element: an auxin response element(AuxRE) in p S and an auxin response region(Aux RR) in p L, respectively. ARF24binding affinity to Aux RR was much higher compared with Aux RE. Overall, our results establish that the small G-protein Zm Arf2 positively regulates maize kernel size and reveals the mechanism of its expression regulation.展开更多
The development of a hook-like structure at the apical part of the soil-emerging organs has fascinated botanists for centuries,but how it is initiated remains unclear.Here,we demonstrate with highthroughput infrared i...The development of a hook-like structure at the apical part of the soil-emerging organs has fascinated botanists for centuries,but how it is initiated remains unclear.Here,we demonstrate with highthroughput infrared imaging and 2-D clinostat treatment that,when gravity-induced root bending is absent,apical hook formation still takes place.In such scenarios,hook formation begins with a de novo growth asymmetry at the apical part of a straightly elongating hypocotyl.Remarkably,suchde novo asymmetric growth,but not the following hook enlargement,precedes the establishment of a detectable auxin response asymmetry,and is largely independent of auxin biosynthesis,transport and signaling.Moreover,we found that functional cortical microtubule array is essential for the following enlargement of hook curvature.When microtubule array was disrupted by oryzalin,the polar localization of PIN proteins and the formation of an auxin maximum became impaired at the to-be-hook region.Taken together,we propose a more comprehensive model for apical hook initiation,in which the microtubuledependent polar localization of PINs may mediate the instruction of growth asymmetry that is either stochastically taking place,induced by gravitropic response,or both,to generate a significant auxin gradient that drives the full development of the apical hook.展开更多
Auxin is a key hormone performing a wealth of functions throughout the life cycle of plants. It acts largely by regulating genes at the transcriptional level through a family of transcription factors called auxin resp...Auxin is a key hormone performing a wealth of functions throughout the life cycle of plants. It acts largely by regulating genes at the transcriptional level through a family of transcription factors called auxin response factors (ARFs). Even though all ARF monomers analyzed so far bind a similar DNA sequence, there is evidence that ARFs differ in their target genomic regions and regulated genes. Here, we report the use of position weight matrices (PWMs) to model ARF DNA binding specificity based on published DNA affinity purification sequencing (DAP-seq) data. We found that the genome binding of two ARFs (ARF2 and ARF5/ Monopteros [MP]) differ largely because these two factors have different preferred ARF binding site (ARFbs) arrangements (orientation and spacing). We illustrated why PWMs are more versatile to reliably identify ARFbs than the widely used consensus sequences and demonstrated their power with biochemical experiments in the identification of the regulatory regions o1IAA19, an well-characterized auxin-responsive gene. Finally, we combined gene regulation by auxin with ARF-bound regions and identified specific ARFbs configurations that are over-represented in auxin-upregulated genes, thus deciphering the ARFbs syntax functional for regulation. Our study provides a general method to exploit the potential of genome-wide DNA binding assays and to decode gene regulation.展开更多
文摘The plant hormone auxin plays a critical role in regulating plant growth and development. Recent advances have been made in the understanding of auxin response pathways, primarily by the characterization of auxin response mutants in Arabidopsis. In addition, microRNAs （miRNAs） have been shown to be critical regulators of genes important for normal plant development and physiology. However, little is known about possible interactions between miRNAs and hormonal signaling during normal development. Here we show that an Arabidopsis microRNA, miR167, which has a complementary sequence to a portion of the A UXINRESPONSE FACTOR6 （ARF6） and ARF8 mRNAs, can cause transcript degradation for ARF8, but not for ARF6. We report phenotypic characterizations of 35S：：MIR167b transgenic lines, and show that severe 35S：：MIR167b transgenic lines had phenotypes similar to those of an arf6 arf8 double mutant. The transgenic phenotypes suggest that miR167 may repress ARF6 at the level of translation. We demonstrate that the transgenic plants are defective in all four whods of floral organs. In the transgenic flowers, filaments were abnormally short, anthers could not properly release pollen, and pollen grains did not germinate. Our results provide an important link between the miRNA-mediated regulatory pathway of gene expression and the auxin signaling network promoting plant reproductive development.
基金financially supported by the National Natural Science Foundation of China and the Israel Science Foundation(NSFC-ISF32061143005)+2 种基金National Natural Science Foundation of China(32000225)Natural Science Foundation of Shandong Province(ZR2020QC036)China Postdoctoral Science Foundation(2020M682165)。
文摘Auxin,one of the first identified and most widely studied phytohormones,has been and will remain a hot topic in plant biology.After more than a century of passionate exploration,the mysteries of its synthesis,transport,signaling,and metabolism have largely been unlocked.Due to the rapid development of new technologies,new methods,and new genetic materials,the study of auxin has entered the fast lane over the past 30 years.Here,we highlight advances in understanding auxin signaling,including auxin perception,rapid auxin responses,TRANSPORT INHIBITOR RESPONSE 1 and AUXIN SIGNALING F-boxes(TIR1/AFBs)-mediated transcriptional and non-transcriptional branches,and the epigenetic regulation of auxin signaling.We also focus on feedback inhibition mechanisms that prevent the over-amplification of auxin signals.In addition,we cover the TRANSMEMBRANE KINASE-mediated non-canonical signaling,which converges with TIR1/AFBs-mediated transcriptional regulation to coordinate plant growth and development.The identification of additional auxin signaling components and their regulation will continue to open new avenues of research in this field,leading to an increasingly deeper,more comprehensive understanding of how auxin signals are interpreted at the cellular level to regulate plant growth and development.
基金supported by grants from the National Natural Science Foundation of China(31570243No.31622008No.31421062)
文摘The changes in external K^＋ concentration affect plant root growth. However, the molecular mechanism for perceiving a K^＋ signal to modulate root growth remains unknown. It is hypothesized that the K^＋ channel AKTI is involved in low K^＋ sensing in the Arabidopsis root and subsequent regulation of root growth. Along with the decline of external K^＋ concentration, the primary root growth of wild-type plants was gradually inhibited. However, the primary root of the akt1 mutant could still grow under low K^＋（LK） conditions. Application of NAA inhibited akt1 root growth, but promoted wild-type root growth under LK conditions. By using the ProDR5：GFP and ProPIN1：PIN1-GFP lines, we found that LK treatment reduced auxin accumulation in wild-type root tips by degrading PIN1 proteins, which did not occur in the akt1 mutant. The LK-induced PIN1 degradation may be due to the inhibition of vesicle trafficking of PIN1 proteins. In conclusion, our findings indicate that AKT1 is required for an Arabidopsis response to changes in external K^＋, and subsequent regulation of K^＋-dependent root growth by modulating PINt degradation and auxin redistribution in the root.
基金funded by grants from the National Natural Science Foundation of China(32060451)Natural Science Foundation of Inner Mongolia(2022ZD11)+1 种基金Zhejiang Provincial Natural Science Foundation of China(LZ19C020001)Applied Technology Research and Development Foundation of Inner Mongolia(2021PT0001)。
文摘Auxin is a crucial phytohormone that has various effects on the regulators of plant growth and development.Auxin signal transduction is mainly controlled by two gene families:auxin response factor(ARF)and auxin/indole-3-acetic acid(Aux/IAA).ARFs are plant-specific transcription factors that bind directly to auxin response elements in the promoters of auxinresponsive genes.ARF proteins contain three conserved regions:a conserved N-terminal B3DNA-binding domain,a variable intermediate middle region domain that functions in activation or repression,and a C-terminal domain including the Phox and Bem1p region for dimerization,similar to theⅢandⅣelements of Aux/IAA,which facilitate protein–protein interaction through homodimerization of ARF proteins or heterodimerization of ARF and Aux/IAA proteins.In the two decades following the identification of the first ARF,23 ARF members have been identified and characterized in Arabidopsis.Using whole-genome sequencing,22,25,23,25,and 36 ARF genes have been identified in tomato,rice,wheat,sorghum,and maize,respectively,in addition to which the related biofunctions of some ARFs have been reported.ARFs play crucial roles in regulating the growth and development of roots,leaves,flowers,fruits,seeds,responses to biotic and abiotic stresses,and phytohormone signal crosstalk.In this review,we summarize the research progress on the structures and functions of ARFs in Arabidopsis,tomato,and cereal crops,to provide clues for future basic research on phytohormone signaling and the molecular design breeding of crops.
基金This work was supported by the National Natural Science Foundation of China （No. 90717001, 30721061, 30425029） and Science and Technology Commission of Shanghai Municipality （08XD14049）.We thank Jian Xu （Utrecht University, Netherlands） for providing Arabidopsis seeds containing DR5-GUS and PIN2-EGFP expression cassettes. No conflict of interest declared,
文摘Overexpression of membrane steroid binding protein 1 （MSBP1） stimulates the root gravitropism and antigravitropism of hypocotyl, which is mainly due to the enhanced auxin redistribution in the bending regions of hypocotyls and root tips. The inhibitory effects by 1-N-naphthylphthalamic acid （NPA）, an inhibitor of polar auxin transport, are suppressed under the MSBP1 overexpression, suggesting the positive effects of MSBP1 on polar auxin transport. Interestingly, sub-cellular localization studies showed that MSBP1 is also localized in endosomes and observations of the membraneselective dye FM4-64 revealed the enhanced vesicle trafficking under MSBP1 overexpression. MSBPl-overexpressing seedlings are less sensitive to brefeldin A （BFA） treatment, whereas the vesicle trafficking was evidently reduced by suppressed MSBP1 expression. Enhanced MSBP1 does not affect the polar localization of PIN2, but stimulates the PIN2 cycling and enhances the asymmetric PIN2 redistribution under gravi-stimulation. These results suggest that MSBP1 could enhance the cycling of PIN2-containing vesicles to stimulate the auxin redistribution under gravi-stimulation, providing informative hints on interactions between auxin and steroid binding protein.
基金supported by the Hainan Provincial Joint Project of Sanya Yazhou Bay Science and Technology City(2021JJLH0045)the Natural Science Foundation of Zhejiang Province(LTGN23C130001)+2 种基金National Key R&D Program of China(2020YFE0202300)the Key Research and Development Program of Zhejiang Province(2021C02056)the Agricultural Science and Technology Innovation Program(CAAS‐ASTIP‐2013‐CNRRI).
文摘Tiller angle is a key agricultural trait that establishes plant architecture,which in turn strongly affects grain yield by influencing planting density in rice.The shoot gravity response plays a crucial role in the regulation of tiller angle in rice,but the underlying molecular mechanism is largely unknown.Here,we report the identification of the BIG TILLER ANGLE2(BTA2),which regulates tiller angle by controlling the shoot gravity response in rice.Loss-of-function mutation of BTA2 dramatically reduced auxin content and affected auxin distribution in rice shoot base,leading to impaired gravitropism and therefore a big tiller angle.BTA2 interacted with AUXIN RESPONSE FACTOR7(ARF7)to modulate rice tiller angle through the gravity signaling pathway.The BTA2 protein was highly conserved during evolution.Sequence variation in the BTA2 promoter of indica cultivars harboring a less expressed BTA2 allele caused lower BTA2 expression in shoot base and thus wide tiller angle during rice domestication.Overexpression of BTA2 significantly increased grain yield in the elite rice cultivar Huanghuazhan under appropriate dense planting conditions.Our findings thus uncovered the BTA2-ARF7 module that regulates tiller angle by mediating the shoot gravity response.Our work offers a target for genetic manipulation of plant architecture and valuable information for crop improvement by producing the ideal plant type.
基金funded by the National Natural Science Foundation of China(30971557,30971816,and31300996)the Guangdong Natural Science Foundation(S2011010001433)
文摘Auxin plays critical roles in root formation and development. The components involved in this process, however, are not well understood. Here, we newly identified a peptide encoding gene, auxin-responsive endogenous polypeptide 1 （AREP1）, which is induced by auxin, and mediates root development in Arabidopsis. Expression of AREP1 was specific to the cotyledon and to root and shoot meristem tissues. Amounts of AREP1 transcripts and AREP1-green fluorescent protein fusion proteins were elevated in response to indoleacetic acid treatment. Suppression of AREP1 through RNAi silencing resulted in reduction of primary root length, increase of lateral root number, and expansion of adventitious roots, compared to the observations in wild-type plants in the presence of auxin. By contrast, transgenic plants overexpressing AREP1 showed enhanced growth of the primary root under auxin treatment. Additionally, rootmorphology, including lateral root number and adventitious roots, differed greatly between transgenic and wildtype plants. Further analysis indicated that the expression of auxin-responsive genes, such as IAA3, IAA7, IAA17, GH3.2, GH3.3, and SAUR-AC1, was significantly higher in AREP1 RNAi plants, and was slightly lower in AREP1 overexpressing plants than in wildtype plants. These results suggest that the novel endogenous peptide AREP1 plays an important role in the process of auxinmediated root development.
文摘Plant growth regulators are biologically active signaling molecules that regulate a number of plant physiological processes. Auxin(indole-3-acetic acid) is an important plant growth regulator and is synthesized within plant tissues through L-tryptophan(L-TRP)-dependent and-independent pathways. It has been found that plants respond to exogenously applied L-TRP due to insufficient endogenous auxin biosynthesis. The exogenous application of L-TRP is highly significant for normal plant growth and development.L-tryptophan is applied through foliar spray, seed priming, and soil application. Soil-applied L-TRP is either directly taken up by plants or metabolized to auxin by soil microbiota and then absorbed by plant roots. Similarly, foliar spray and seed priming with L-TRP stimulates auxin synthesis within plants and improves the growth and productivity of agricultural crops. Furthermore, L-TRP contains approximately 14% nitrogen(N) in its composition, which is released upon its metabolism within a plant or in the rhizosphere and plays a role in enhancing crop productivity. This review deals with assessing crop responses under the exogenous application of L-TRP in normal and stressed environments, mode of action of L-TRP, advantages of using L-TRP over other auxin precursors, and role of the simultaneous use of L-TRP and auxin-producing microbes in improving the productivity of agricultural crops. To the best of our knowledge, this is the first review reporting the importance of the use of L-TRP in agriculture.
文摘Light is an environmental signaling,whereas Aux/IAA proteins and Auxin Response Factors(ARFs)are regulators of auxin signalling.Aux/IAA proteins are unstable,and their degradation dependents on 26S ubiquitin-proteasome and is promoted by Auxin.Auxin binds directly to a SCF-type ubiquitin-protein ligase,TIR1,facilitates the interaction between Aux/IAA proteins and TIR1,and then the degradation of Aux/IAA proteins.A few studies have reported that some ARFs are also unstable proteins,and their degradation is also mediated by 26S proteasome.In this study,by using of antibodies recognizing endogenous ARF7 proteins,we found that protein stability of ARF7 was affected by light.By expressing MYC tagged ARF activators in protoplasts,we found that degradation of ARF7 was inhibited by 26 proteasome inhibitors.In addition,at least ARF5 and ARF19 were also unstable proteins,and degradation of ARF5 via 26S proteasome was further confirmed by using stable transformed plants overexpressing ARF5 with a GUS tag.
基金supported by Zhongyuan Scholars in Henan Province (22400510003 to YL)the National Natural Science Foundation of China (31771812, 31971962, and 32272129 to YL)+1 种基金the Major Public Welfare Projects of Henan Province (201300111100 to YL)Technical System of Maize Industry in Henan Province (HARS-22-02-S to YL)。
文摘Members of the ADP-ribosylation factor family,which are GTP-binding proteins, are involved in metabolite transport, cell division, and expansion.Although there has been a significant amount of research on small GTP-binding proteins, their roles and functions in regulating maize kernel size remain elusive. Here, we identified Zm Arf2 as a maize ADPribosylation factor-like family member that is highly conserved during evolution. Maize zmarf2 mutants showed a characteristic smaller kernel size. Conversely, ZmArf2 overexpression increased maize kernel size. Furthermore, heterologous expression of Zm Arf2 dramatically elevated Arabidopsis and yeast growth by promoting cell division. Using expression quantitative trait loci(e QTL) analysis, we determined that Zm Arf2 expression levels in various lines were mainly associated with variation at the gene locus. The promoters of Zm Arf2 genes could be divided into two types, p S and p L, that were significantly associated with both Zm Arf2 expression levels and kernel size. In yeast-one-hybrid screening, maize Auxin Response Factor 24(ARF24) is directly bound to the Zm Arf2 promoter region and negatively regulated Zm Arf2 expression.Notably, the p S and p L promoter types each contained an ARF24 binding element: an auxin response element(AuxRE) in p S and an auxin response region(Aux RR) in p L, respectively. ARF24binding affinity to Aux RR was much higher compared with Aux RE. Overall, our results establish that the small G-protein Zm Arf2 positively regulates maize kernel size and reveals the mechanism of its expression regulation.
基金funded by the Southern University of Science and Technology for scientific research start-ups(Grant No.Y01226124 to H.G.)National Natural Science Foundation of China(Grant No.31700239 to Y.W.)+1 种基金Shenzhen Science and Technology Innovation Program(Grant No.JCYJ20170817105503416 to W.L.)Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes(SUSTech)(2019KSYS006 to H.G.)。
文摘The development of a hook-like structure at the apical part of the soil-emerging organs has fascinated botanists for centuries,but how it is initiated remains unclear.Here,we demonstrate with highthroughput infrared imaging and 2-D clinostat treatment that,when gravity-induced root bending is absent,apical hook formation still takes place.In such scenarios,hook formation begins with a de novo growth asymmetry at the apical part of a straightly elongating hypocotyl.Remarkably,suchde novo asymmetric growth,but not the following hook enlargement,precedes the establishment of a detectable auxin response asymmetry,and is largely independent of auxin biosynthesis,transport and signaling.Moreover,we found that functional cortical microtubule array is essential for the following enlargement of hook curvature.When microtubule array was disrupted by oryzalin,the polar localization of PIN proteins and the formation of an auxin maximum became impaired at the to-be-hook region.Taken together,we propose a more comprehensive model for apical hook initiation,in which the microtubuledependent polar localization of PINs may mediate the instruction of growth asymmetry that is either stochastically taking place,induced by gravitropic response,or both,to generate a significant auxin gradient that drives the full development of the apical hook.
文摘Auxin is a key hormone performing a wealth of functions throughout the life cycle of plants. It acts largely by regulating genes at the transcriptional level through a family of transcription factors called auxin response factors (ARFs). Even though all ARF monomers analyzed so far bind a similar DNA sequence, there is evidence that ARFs differ in their target genomic regions and regulated genes. Here, we report the use of position weight matrices (PWMs) to model ARF DNA binding specificity based on published DNA affinity purification sequencing (DAP-seq) data. We found that the genome binding of two ARFs (ARF2 and ARF5/ Monopteros [MP]) differ largely because these two factors have different preferred ARF binding site (ARFbs) arrangements (orientation and spacing). We illustrated why PWMs are more versatile to reliably identify ARFbs than the widely used consensus sequences and demonstrated their power with biochemical experiments in the identification of the regulatory regions o1IAA19, an well-characterized auxin-responsive gene. Finally, we combined gene regulation by auxin with ARF-bound regions and identified specific ARFbs configurations that are over-represented in auxin-upregulated genes, thus deciphering the ARFbs syntax functional for regulation. Our study provides a general method to exploit the potential of genome-wide DNA binding assays and to decode gene regulation.
