ABA INSENSITIVE 1 (ABI1) and ABI2 are co-receptors of the phytohormone abscisic acid (ABA). Studies have demonstrated that phosphorylation of multiple amino acids on ABI1/2 augments their ability to inhibit ABA signal...ABA INSENSITIVE 1 (ABI1) and ABI2 are co-receptors of the phytohormone abscisic acid (ABA). Studies have demonstrated that phosphorylation of multiple amino acids on ABI1/2 augments their ability to inhibit ABA signaling in planta. However, whether and how the dephosphorylation of ABI1/2 is regulated to enhance plant sensitivity to ABA remain unknown. In this study, we identified two protein phosphatases, designated ABI1-Dephosphorylating E-clade PP2C 1 (ADEP1) and ADEP2, that interact with ABI1/2. Mutants lacking ADEP1, ADEP2, or both (adep1/2) exhibited reduced ABA inhibition of seed germination and root growth, as well as lower levels of ABA-induced stomatal closure. In addition, ABA-induced accumulation of ABI5 protein and expression of downstream target genes are reduced in the adep1/2 mutant compared with the wild type. These findings suggest that ADEP1/2 function as positive regulators of the ABA signaling pathway. Mass spectrometry analysis and two-dimensional electrophoresis identified Ser117 as a major ABA-induced phosphorylation site on the ABI1 protein. ADEP1/2 can dephosphorylate Ser117, leading to destabilization of the ABI1 protein and increased sensitivity of plants to ABA. Moreover, ABA treatment decreases the abundance of ADEP1/2 proteins. In summary, our study reveals two novel regulatory proteins that modulate ABA signaling and provides new insights into the regulatory network that fine-tunes plant ABA responses.展开更多
The phytohormone abscisic acid （ABA） regulates many key processes in plants, such as seed germina- tion, seedling growth, and abiotic stress tolerance. In recent years, a minimal set of core components of a major AB...The phytohormone abscisic acid （ABA） regulates many key processes in plants, such as seed germina- tion, seedling growth, and abiotic stress tolerance. In recent years, a minimal set of core components of a major ABA signaling pathway has been discovered. These components include a RCAR/PYR/PYL family of ABA receptors, a group of PP2C phosphatases, and three SnRK2 kinases. However, how the interactions between the receptors and their targets are regulated by other proteins remains largely unknown. In a companion paper published in this issue, we showed that ROP11, a member of the plant- specific Rho-like small GTPase family, negatively regulates multiple ABA responses in Arabidopsis. The current work demonstrated that the constitutively active ROP11 （CA-ROP11） can modulate the RCAR1/PYL9-mediated ABA signaling pathway based on reconstitution assays in Arabidopsis thaliana protoplasts. Furthermore, using luciferase complementation imaging, yeast two-hybrid assays, co- immunoprecipitation assays in Nicotiana benthamiana and bimolecular fluorescence complementation assays, we demonstrated that CA-ROP11 directly interacts with ABI1, a signaling component downstream of RCAR1/PYL9. Finally, we provided biochemical evidence that CA-ROP11 protects ABI1 phosphatase activity from inhibition by RCAR1/PYL9 and thus negatively regulates ABA signaling in plant cells. A model of how ROP11 acts to negatively regulate ABA signaling is presented.展开更多
The B3 transcription factors(TFs)in plants play vital roles in numerous biological processes.Although B3 genes have been broadly identified in many plants,little is known about their potential functions in mediating s...The B3 transcription factors(TFs)in plants play vital roles in numerous biological processes.Although B3 genes have been broadly identified in many plants,little is known about their potential functions in mediating seed development and material accumulation.Castor bean(Ricinus communis)is a non-edible oilseed crop considered an ideal model system for seed biology research.Here,we identified a total of 61 B3 genes in the castor bean genome,which can be classified into five subfamilies,including ABI3/VP1,HSI,ARF,RAV and REM.The expression profiles revealed that RcABI3/VP1 subfamily genes are significantly up-regulated in the middle and later stages of seed development,indicating that these genes may be associated with the accumulation of storage oils.Furthermore,through yeast one-hybrid and tobacco transient expression assays,we detected that ABI3/VP1 subfamily member RcLEC2 directly regulates the transcription of RcOleosin2,which encodes an oil-body structural protein.This finding suggests that RcLEC2,as a seed-specific TF,may be involved in the regulation of storage materials accumulation.This study provides novel insights into the potential roles and molecular basis of B3 family proteins in seed development and material accumulation.展开更多
基金supported by grants from the National Natural Science Foundation of China(32370331)the Natural Science Foundation of Hebei Province,China(C2023205049)to Y.S.
文摘ABA INSENSITIVE 1 (ABI1) and ABI2 are co-receptors of the phytohormone abscisic acid (ABA). Studies have demonstrated that phosphorylation of multiple amino acids on ABI1/2 augments their ability to inhibit ABA signaling in planta. However, whether and how the dephosphorylation of ABI1/2 is regulated to enhance plant sensitivity to ABA remain unknown. In this study, we identified two protein phosphatases, designated ABI1-Dephosphorylating E-clade PP2C 1 (ADEP1) and ADEP2, that interact with ABI1/2. Mutants lacking ADEP1, ADEP2, or both (adep1/2) exhibited reduced ABA inhibition of seed germination and root growth, as well as lower levels of ABA-induced stomatal closure. In addition, ABA-induced accumulation of ABI5 protein and expression of downstream target genes are reduced in the adep1/2 mutant compared with the wild type. These findings suggest that ADEP1/2 function as positive regulators of the ABA signaling pathway. Mass spectrometry analysis and two-dimensional electrophoresis identified Ser117 as a major ABA-induced phosphorylation site on the ABI1 protein. ADEP1/2 can dephosphorylate Ser117, leading to destabilization of the ABI1 protein and increased sensitivity of plants to ABA. Moreover, ABA treatment decreases the abundance of ADEP1/2 proteins. In summary, our study reveals two novel regulatory proteins that modulate ABA signaling and provides new insights into the regulatory network that fine-tunes plant ABA responses.
基金supported by the 973National Basic Research Program of the Ministry of Science and Technology of China(2009CB119100)the National Natural Science Foundation of China(90717121)
文摘The phytohormone abscisic acid （ABA） regulates many key processes in plants, such as seed germina- tion, seedling growth, and abiotic stress tolerance. In recent years, a minimal set of core components of a major ABA signaling pathway has been discovered. These components include a RCAR/PYR/PYL family of ABA receptors, a group of PP2C phosphatases, and three SnRK2 kinases. However, how the interactions between the receptors and their targets are regulated by other proteins remains largely unknown. In a companion paper published in this issue, we showed that ROP11, a member of the plant- specific Rho-like small GTPase family, negatively regulates multiple ABA responses in Arabidopsis. The current work demonstrated that the constitutively active ROP11 （CA-ROP11） can modulate the RCAR1/PYL9-mediated ABA signaling pathway based on reconstitution assays in Arabidopsis thaliana protoplasts. Furthermore, using luciferase complementation imaging, yeast two-hybrid assays, co- immunoprecipitation assays in Nicotiana benthamiana and bimolecular fluorescence complementation assays, we demonstrated that CA-ROP11 directly interacts with ABI1, a signaling component downstream of RCAR1/PYL9. Finally, we provided biochemical evidence that CA-ROP11 protects ABI1 phosphatase activity from inhibition by RCAR1/PYL9 and thus negatively regulates ABA signaling in plant cells. A model of how ROP11 acts to negatively regulate ABA signaling is presented.
基金National Natural Science Foundation of China(31661143002,81760507,31571709,31771839,31701123 and 31501034)Yunnan Applied Basic Research Projects(2016FA011,2016FB060 and 2016FB040)+1 种基金the National R&D Infrastructure and Facility development Program of China"Fundamental Science Data Sharing Platform(DKA 201712-02-16)the 13th Five-year informatization Plan of Chinese Academy of Sciences(No.XXH13506)。
文摘The B3 transcription factors(TFs)in plants play vital roles in numerous biological processes.Although B3 genes have been broadly identified in many plants,little is known about their potential functions in mediating seed development and material accumulation.Castor bean(Ricinus communis)is a non-edible oilseed crop considered an ideal model system for seed biology research.Here,we identified a total of 61 B3 genes in the castor bean genome,which can be classified into five subfamilies,including ABI3/VP1,HSI,ARF,RAV and REM.The expression profiles revealed that RcABI3/VP1 subfamily genes are significantly up-regulated in the middle and later stages of seed development,indicating that these genes may be associated with the accumulation of storage oils.Furthermore,through yeast one-hybrid and tobacco transient expression assays,we detected that ABI3/VP1 subfamily member RcLEC2 directly regulates the transcription of RcOleosin2,which encodes an oil-body structural protein.This finding suggests that RcLEC2,as a seed-specific TF,may be involved in the regulation of storage materials accumulation.This study provides novel insights into the potential roles and molecular basis of B3 family proteins in seed development and material accumulation.
