低温逆境下钙调控生长素抑制番茄花柄脱落的分子机制

Under low temperature, tomatoes and some other thermophilic vegetables will be some physiology problem leading to flower and fruit abscission. It has been a serious problem for limiting greenhouse vegetables production. The earlier study has revealed auxin and calcium plays an important regulatory role on delay abscission, but their molecular mechanism on abscission under low is still not clear. For this purpose, the project aimes to elucidate the molecular mechanism of calcium regulated auxin in inhibiting the abscission of tomato flower pedicel under low-temperature stress. At beginning, the effects of low temperature stress on the synthesis, conjugation and hydrolysis, transport, signal transduction and calcium signal were studied, screened the low temperature altered key sites. Secondly, on the basis of this, the screened genes of the low temperature mediated were identified by transgenic methods. At last, using the yeast two-hybrid and co-immunoprecipitation methods to determine whether the calcium-related members that activate the auxin function by directly regulate the auxin-related genes, and conclude the molecular mechanism of calcium regulated auxin inhibits abscission.

番茄等果菜类蔬菜落花落果的原因很多，其中低温是重要因素之一，这在冬春设施果菜生产中尤为突出，严重影响了产量。许多研究表明，钙具有促进生长素抑制植物器官脱落的作用，但有关钙调控生长素抑制低温诱导植物器官脱落的分子机制尚不明确。本项目在前期初步明确钙与生长素防止番茄花柄脱落的基础上，通过研究低温逆境对番茄花器官生长素合成、轭合与水解、运输、信号传导及钙调控作用的影响，明确低温下生长素抑制番茄花柄脱落功能降低的关键位点及钙信号成员的变化规律；在此基础上，通过转基因手段明确受低温调控的基因位点影响生长素功能的机理和调控脱落发生的作用模式；并通过明确钙素调控的生长素功能基因位点，利用酵母双杂交和免疫共沉淀方法，检测激活生长素功能的钙素相关成员是否直接调控生长素相关作用基因，从而明确低温逆境下钙调控生长素抑制番茄花器官脱落的分子机制。

番茄（Solanum lycopersicum）是栽培较为广泛的喜温蔬菜之一，在北方栽培过程中经常遭受低温胁迫，尤其是设施冬春茬栽培更是如此。低温胁迫可导致番茄落花落果，严重影响番茄产量。因此明确低温下番茄的落花落果机制，并提出科学合理的防治技术，对番茄生产具有重要意义。本研究发现低温导致脱落的根本原因是生长素含量降低和乙烯含量升高。其一生长素含量降低主要是低温使花粉败育，抑制生长素合成基因SlFYZ3, SlFYZ5和YUCCAs的表达，导致生长素含量降低。同时低温通过影响EXO70降低了生长素的运输，同时PIN的亚细胞定位改变，使大量生长素停留在心室，导致离区生长素含量降低。另外乙烯含量升高主要是EIL3激发乙烯信号，ACS1表达加速乙烯的合成。基于本研究的结果，在番茄生产中，将生长素和钙共同施用是预防低温诱发脱落的有效防治措施。