干旱胁迫下在IAA诱导大豆抗氧化酶中Ca2+/CaM与H2O2的关系的研究

Drought is a serious problem existed in agricultural production. Study of the mechanism of plant drought resistance will provide an important safeguard for the increase of agricultural production and incomes. Previous studies have shown that the enhanced adaptive ability of plant to stresses was related to phytohormone-induced expression of antioxidant genes and phytohormone-enhanced capacity of antioxidant defense systems. However, it is little work for the roles and signaling of indole-3-acetic acid (IAA) in drought-induced antioxidant defense. Kefeng 1, a soybean (Glycine max [L.] Merr.) cultivar, shows strong resistance to drought stress. A hydroponic experiment is conducted using Kefeng 1 to investigate whether Ca2+/CaM involves IAA-induced antioxidant defense of leaves and what relationship there is between Ca2+/CaM and H2O2 in IAA signaling under drought stress. The main content includes three parts as follows: 1) The roles of Ca2+/CaM in the H2O2-induced antioxidant defense in different subcellular compartments in soybean leaves under drought stress. 2) Effects of drought stress-induced IAA accumulation on mRNA and protein expressions of antioxidant enzymes. 3) The relationship between Ca2+/CaM and H2O2 in IAA-induced mRNA and protein expressions of antioxidant enzymes in soybean leaves exposed to drought stress. Based on this study we may further understand the roles and signaling of IAA in plants in response to drought stress, and provide a theoretical basis for the regulation of plant hormone in the production and cultivation of crop in arid regions.

干旱是农业生产中存在的严重问题，探明植物抗旱机理，将为农业增产增收提供重要保障。已有研究表明，植物适应胁迫能力的提高与激素诱导的抗氧化防护有关。然而，关于干旱胁迫下生长素（IAA）所诱导的抗氧化防护及信号转导机制的研究较少。本项目以耐旱型大豆品种‘科丰1号’为材料，采用水培试验，对干旱胁迫下钙离子/钙调素信号系统（Ca2+/CaM）是否参与IAA诱导大豆叶片抗氧化酶以及过氧化氢（H2O2）与Ca2+/CaM之间的关系进行研究。具体内容包括：干旱胁迫下Ca2+/CaM在IAA诱导大豆叶片各细胞分区抗氧化酶中的作用；干旱胁迫积累的IAA对大豆叶片抗氧化酶mRNA和蛋白表达量的影响；干旱胁迫下在IAA诱导大豆叶片抗氧化酶mRNA和蛋白表达中H2O2与Ca2+/CaM的关系。本项目旨在加深人们对干旱胁迫下IAA信号转导作用的理解，为干旱地区作物栽培的激素调控、干旱条件下大豆的化学调控提供理论依据。

植物适应干旱胁迫能力的提高与生长素（IAA）诱导的抗氧化防护有关。然而，关于干旱胁迫下IAA信号转导在IAA提高抗氧化能力和耐旱性中的作用鲜有研究。因此，本项目通过水培方式对干旱胁迫下IAA在诱导大豆抗氧化能力的作用机制及IAA提高大豆耐旱性的非抗氧化途径进行了研究。首先，明确了干旱胁迫下依赖Ca2+-ATPase产生的Ca2+/CaM在IAA诱导达到抗氧化酶中的作用，发现干旱胁迫诱导的IAA通过激活Ca2+-ATPase活性，增强下游信号Ca2+/CaM，Ca2+/CaM诱导NADPH氧化酶和细胞壁过氧化物酶，进而导致干旱早期H2O2积累。早期H2O2积累作为信号上调细胞溶质、叶绿体和线粒体中超氧化物歧化酶（SOD）、抗坏血酸氧化酶（APX）和谷胱甘肽还原酶（GR）活性和细胞溶质中抗坏血酸（AsA）和谷胱甘肽（GSH）含量，抑制干旱后期活性氧（ROS）的过度积累，从细胞水平上揭示了Ca2+/CaM是如何介导干旱胁迫积累的IAA诱导抗氧化酶的。其次，采用化控手段，明确了干旱胁迫下IAA和过氧化氢（H2O2）的多重信号作用，结果显示干旱早期H2O2积累也可作为信号在三唑酮（TDM）提高耐旱性中发挥作用；1-萘乙酸（NAA）可同时诱导抗氧化代谢和碳代谢，NAA能够缓解干旱胁迫对大豆的生长抑制，降低干旱胁迫诱导的可溶性糖积累，促进叶片中蔗糖向根系的转运，通过调控碳代谢增强大豆植株对干旱胁迫的耐受性，从而拓宽了对IAA信号作用的认知。最后，通过改变miR393和TIR1基因表达水平，明确了IAA信号转导在IAA诱导大豆抗氧化能力的作用，结果发现干旱胁迫下miR393a、miR393h/i/j/k和TIR1A、TIR1B、TIR1C、TIR1D表达水平增加，而改变miR393a和TIR1A表达水平可以调控大豆耐旱性；沉默或超表达miR393可改变TIR1A表达水平，沉默miR393a或超表达TIR1A能够提高胁迫早期H2O2含量，增加Ca2+/CaM含量、抗氧化能力，降低膜脂过氧化程度，而超表达miR393a或沉默TIR1A后所起的作用恰好相反，表明miR393a-TIR1A模式在大豆响应干旱胁迫中起到了调控作用，从而加深了人们对干旱胁迫下IAA信号转导作用的理解，为干旱条件下大豆的化学调控提供理论依据。