乙烯信号传导调控植物耐盐性新组分的鉴定

Increasing investigations reveal that ethylene biosynthesis and signaling have important roles in the regulation of plant development and salt response, but the detailed molecular mechanism in the process is not clear. Under the support of the Plant Hormone Research Grand Project, our previous researches proved that the ABA-mediated HY5-AtERF11 transcriptional cascade regulates ethylene biosynthesis, which consequently affects the growth of roots and hypocotyls. Further studies showed that ethylene signaling molecule EIN3-ESE1 affects plant salt tolerance. Moreover, photomorphogenesis factor COP1 genetically functions downstream of ethylene signaling component EIN3 in salt response and hypocotyl growth. For the HY5 is one of the direct substrates of COP1 in photomorphogenesis, further investigations showed that seed germination and the green cotyledon was reduced under salt stress in hybrid eto2×35S::HY5, compared to eto2, while ein2 hy5 double mutant rescued the green cotyledon of ein2 to the level of Col-0 under salt stress, and the seed germination was higher in etr1-1 hy5 and ein3-1 hy5 double mutants than in Col-0 and in single mutants of etr1-1 and ein3-1, respectively, revealing that the HY5 is a genetical downstream of EIN3 in ethylene-modulated salt response. And this regulation is through the promotion of ethylene on the HY5 protein instability. Based on the above results, we speculate that ethylene mediating unknown factor(s) affect(s) the shuttle of COP1 between nucleus and cytoplasm, which subsequently results in the instability of HY5 protein, therefore, we hypothesis that COP1-HY5 complex might be a novel signal molecule in ethylene-modulated plant salt tolerance. The present project is planned to conduct the following investigations. Firstly, through biochemical detections of COP1 and HY5 in ethylene signaling mutants, we will understand whether COP1-HY5 complex functions in the ethylene signal-modulated salt tolerance and root growth. Then we will use the double mutants of cop1 and hy5 with ethylene related mutants or transgenic lines to compare the response to salt, root and hypocotyl growth at different developmental stages, which will evidence how COP1-HY5 complex will be involved in the ethylene signal-modulated salt tolerance and root growth. Next, after the assessment of how ethylene causes COP1 nucleocytoplasmic shuttling with COP1-GUS or COP1-GFP transgenic lines, we will identify the interaction of COP1 with ethylene signaling molecule, the possible candidate is the C terminal of EIN2 (CEBD), in vitro and in vivo. Furthermore, through analyzing the transcriptional profiles of double mutants ein3 hy3 and ein3 cop1 and transgenic line ein2-5CEND overexpressing CEND in ein2-5 background in response to ethylene, light/dark and ABA, we will clarify the molecular basis of how COP1-HY5 complex integrates ethylene and light signaling pathways in salt response.

乙烯合成及信号传导在植物生长发育和逆境胁迫应答中具有重要的调控作用，但其调控的分子机制不清楚。在植物激素重大研究计划资助下，我们发现ABA介导光形态建成因子HY5转录级联乙烯反应因子AtERF11调控乙烯合成并影响根和下胚轴生长发育；而乙烯信号分子EIN3-ESE1转录调控植物耐盐性。进一步研究表明光形态建成因子COP1在EIN3下游调控植物耐盐性，且乙烯还调控HY5蛋白稳定性影响耐盐性，表明乙烯可能介导某种未知因子促进COP1核质穿梭影响HY5稳定性。推测COP1-HY5复合体可能是乙烯信号调控植物耐盐性的新组分。本项目拟在以上研究基础上，通过分析COP1-HY5复合体参与乙烯信号传导调控植物耐盐性，确认其在乙烯信号传导中的功能及其可能的位置，进而鉴定并剖析乙烯相关未知因子促进COP1核质穿梭导致HY5降解的遗传和生化基础，以期阐明HY5整合光和乙烯调控植物耐盐性和生长发育的分子基础。

本项目的研究目标是阐明拟南芥光信号复合体COP1-HY5参与乙烯信号传导调控植物耐盐性和生长发育的分子基础。通过3年的实施，我们圆满地完成了预期的研究内容。研究表明光信号分子COP1-HY5复合体在EIN3下游参与乙烯信号调控的、盐胁迫条件下的种子萌发；乙烯和盐胁迫拮抗调控了COP1核-质穿梭，进而调控HY5蛋白的稳定性以及ABI5的转录，以及胚根的发育；且乙烯可以在光下促进COP1入核、并介导蛋白酶体途径降解HY5，导致下胚轴伸长生长，表明光信号分子COP1-HY5复合体不仅参与乙烯信号传导调控盐胁迫下的种子萌发，而且还调控幼苗下胚轴的伸长生长。进一步的研究还发现另外一个光信号分子CSN5B与维生素C生物合成因子VTC1互作，导致黑暗下VTC1的降解；且这种调控作用影响维生素C的合成，进而改变了植物的耐盐性及幼苗生长发育；且乙烯和ABA转录调控了维生素C的生物合成(未发表结果)。此外，我们还发表了6篇论文，包括高水平的SCI论文4篇；国际国内学术报告11次；引进中国农科院创新人才1名，培养研究员1名、研究生5名。