ACC合酶和IAA动态平衡在NaCl干预拟南芥根形态建成时对话机制

盐胁迫干涉植物激素IAA与乙烯对话而干扰植株生长发育. 已知ACS酶控制乙烯前体ACC生物合成,IAA共轭物合成酶（ICS）调控IAA信号转导,但迄今仍缺乏2种酶家族成员的活性关系证据. 前期研究获得1个介导IAA运输的ICS功能缺失拟南芥突变体ics株系, NaCl处理时, ics幼苗根形态建成明显不同于野生型, 但其根部ACS2基因转录活性大幅提高. 推测ACS2参与盐刺激的ics幼苗根形态建成. 本项目拟创建ICS回补和超表达等相关株系, 综合运用分子、生化、细胞生物学等相关技术, 在盐处理条件下, ① 比较各株系根生长发育表型; ②揭示ICS表达与根部IAA分布的关系; ③解析各株系ACS2基因表达、蛋白二聚体组分与结构特点，ACS2酶活性与ACC/乙烯产生与分布的关系; ④监测ACS2与ICS互作特点. 以期揭示IAA共轭物合成酶和ACS酶活性响应盐胁迫并调控根形态建成的机制.

Salt stress obstructs plant hormone IAA and ethylene signaling invovled in plant growth and development. Given that 1-aminocy clopropane-1- carboxylate (ACC) is the precursor of ethylene, ACC synthase (ACS) is the rate-limiting enzyme of ACC biosynthesis, while IAA conjugate synthetase (ICS) directs IAA homeostasis. It remains to be clarified how activation of ACS isoform talk with ICS-mediated IAA transport and distribution in root cells. Our previous studies showed that NaCl-stimulated seedling root morphogenesis was different from the Arabidopsis loss-of-function ics mutant to wild type, but the IAA distribution in ics seedling roots showed no evident modification, and that the transcription of ACS2 gene evidently increased in ics root compared to the controls, suggesting that NaCl integrated ICS and ACS2 signaling to intrude Arabidopsis seedling root growth and development. After creating the diverse ICS expressing lines, including ICS-complemented plant, ICS over-expression plant, and double mutant icsacs2-1 plant, we try to ① verify the phenotype of ics root morphogenesis in response to NaCl stimuli compared to the ICS-expressed plants; ② evaluate the space-time specificity of the expression of ACS2 and ICS genes involving in the tissue-specificity distribution of IAA, ACC and ethylene; ③ employ transient expression, BiFC or CO-IP method to explore which was the half of the ACS2 protein dimers, and how activation of ACS2 isozyme reciprocally regulated with ICS-mediated IAA distribution in response to NaCl stimuli. These researches could disclose the role of the IAA conjugate and ACS2 isozyme in the processes of Arabidopsis seedling root morphogenesis in response to NaCl stress.