烯效唑对遮阴降低粳稻抗倒伏能力的缓解作用及其机制

The middle and lower reaches of the Yangtze River is an important japonica rice planting area in China. Low PAR occurs occasionally, which increased the lodging risk and affecting the high and stable yield of rice. We found that spraying of uniconazole under weak light could reduce lodging. However, it is unclear how uniconazole increases the anti-lodging ability of rice and its mechanism. In this project, taken two different rice japonica varieties, Wuyunjing23(insensitive to weak light and lodging-resistant) and W3668(sensitive to weak light and lodging-susceptible) as materials, artificial shading experiments will be carried out to simulate the weak light and different uniconazole concentrations will be set up to explore the effects of weak light on the physical and mechanical characteristics of rice stem, morphology, carbohydrates content and distribution, and hormones related to plant growth. Quantitative PCR, RNA-seq and iTRAQ technologies will also be applied to determine the influence of weak light on the expression pattern of key regulatory genes and proteins participating in carbon metabolism, which will reveal the effects of weak light on rice lodging resistance and its mechanism from the aspects of the structure, hormone, and gene expression. Furthermore, the alleviating effects of uniconazole on lodging resistance of Japonica rice stem will be studied by mainly researching on hormone metabolism and gene expression. The results can provide technical support and scientific theoretical basis for high and stable yield of rice under the condition of climate change.

长江中下游地区是我国重要的粳稻种植区，寡照天气时有发生，倒伏风险增大，从而影响水稻的高产稳产。前期研究发现弱光寡照下喷施烯效唑具有防倒伏效果，但其作用机制是什么还不清楚。本项目以武运粳23（对弱光钝感、抗倒）和W3668（对弱光敏感、易倒伏）为研究材料，采用人工遮荫模拟弱光梯度试验，设置不同的烯效唑喷施处理，分析弱光对粳稻茎秆物理力学特征、形态结构、碳组分含量和分布、以及生长激素的影响，并利用荧光定量PCR、RNA-seq和iTRAQ测序技术研究弱光对碳积累过程中碳代谢关键调控基因和蛋白的表达差异，从结构、激素、基因表达多角度揭示弱光对粳稻茎秆抗倒能力的主要影响途径及机制；在此基础上，进一步比较分析烯效唑对粳稻茎秆抗倒能力的调控作用，重点从激素代谢和基因表达两个方面解析烯效唑对弱光降低粳稻抗倒伏能力的缓解作用机制。研究结果可为气候变化条件下水稻的高产稳产提供技术上的支撑和科学理论依据。

倒伏是水稻高产、优质的重要限制因子。抗倒伏能力作为水稻植株的重要理学性状，与茎秆的形态结构和强度密切相关。生育期内阴雨寡照天气对水稻生长发育产生不利影响，外源调节物质作为水稻栽培生产过程中的重要栽培措施，两者均在影响和调控水稻茎秆抗倒伏性中起到了重要作用。本研究在拔节到抽穗期设置正常光照和遮荫处理，遮荫采用黑色遮阳网，透光率约40%。设置了正常光照和遮荫条件烯效唑处理。从力学特征、茎秆形态、解剖结构、理化分析、组织分析、生化分析和转录组学等系统生物学技术手段，从基因转录、蛋白质表达、物质代谢和形态结构等多层次、多角度探索细胞壁合成的基因-代谢网络，旨在揭示遮荫和外源调节物质对粳稻茎秆抗倒伏性的影响机理。本研究结果表明：烯效唑处理降低遮荫条件下株高、重心高和基部第二节间长，增加基部节间重、直径和壁厚，提高茎秆抗折力，降低倒伏风险。遮荫处理降低节间表皮机械组织的厚度和厚壁细胞壁厚度，增加薄壁细胞长度，降低细胞宽度。烯效唑处理显著增加机械组织厚度，降低薄壁细胞长度，排列紧密，其正常光照和遮荫条件下变化趋势一致，其机理是烯效唑促进了细胞壁结构物质木质素、纤维素和半纤维素含量的积累导致细胞形态的改变。采用组学分析表明，大量的差异基因和蛋白参与了碳水化合物代谢、细胞壁形成和激素合成相关的路径。烯效唑可以缓解遮荫对木质素生物合成路径中的基因表达的抑制作用；同时显著影响了纤维素、半纤维素合成途径以及蔗糖代谢的基因和蛋白表达。遮荫处理通过调节激素信号转导差异基因表达介导IAA、Zeatin、TZR、IPA、GA4和GA7的合成，导致茎壁细胞层数减少。烯效唑处理下调遮荫条件下糖分解方向基因表达抑制蔗糖分解酶活性，增加节间中蔗糖含量，调控细胞内糖浓度变化，导致细胞形态改变，增加茎秆机械强度和抗倒伏性。