miR475介导GL2调控根毛发育提高吴屯杨耐盐性的机制研究

吴屯杨是我国“三北”及北方沿海地区主要的造林树种，具有耐盐碱、耐干旱能力强的特点。转录因子GL2下游靶基因RHD6可调控根毛发育从而影响植物耐盐性，但其miRNA调控机制仍不清楚。前期发现吴屯杨miR475靶向GL2，本项目以盐胁迫下抗性存在明显差异的不同种质为材料，利用超微结构观测、双荧光素酶报告基因检测和qRT-PCR等手段，通过对根毛形态的观察及miR475、GL2和RHD6基因表达的分析，明确三者间的调控关系及其对根毛发育的影响；结合过表达及沉默的方法，比较转化miR475和GL2植株及对照植株中RHD6基因表达量、根毛形态和数量及抗性生理指标的差异，揭示miR475介导GL2调控根毛发育提高植物耐盐性的生理及分子机制。这将首次阐明“miR475-GL2-RHD6”模块在吴屯杨耐盐中的作用，可为植物miR475调控GL2提供直接例证，对深入理解miRNA响应盐胁迫机制具有重要意义。

Populus wutunensis with strong tolerance to salt stress and drought stress, is one of major tree species for afforestation in three northern regions and northern coastal regions of China. The transcription factor GL2 downstream target gene RHD6 can affect salt toleranceby regulating root hair development. However, its miRNA regulatory mechanism remains unclear. In our previous research, it was found that miR475 of Populus wutunensis was able to target GL2. Based on these previous results, we will further study the relationship of gene expression of miR475, GL2 and RHD6 on the root hair development. In this project, various germplasms with obvious differences in resistant to salt stress are chosen as treated samples. The form of root hair is obtained by using ultrastructure observation technology. The analysis of gene expression of miR475, GL2, and RHD6 is achieved by using the methods of dual-luciferase reporter gene assay and qRT-PCR. Over-expression method and silencing method are used. Comparing the quantity of RHD6 gene expression, the morphology and quantity of root hair as well as the resistance physiological index between the transformed miR475 and GL2 plants and the control plants, the physiological and molecular mechanisms of miR475 mediates GL2 to regulate root hair development in salt tolerance improvement are revealed. This study is the first to demonstrate the effect of "miR475-GL2-RHD6" module on salt tolerance of Populus wutunensis, which may provide a direct example that GL2 can be regulated by miR475 in plants. This is of great significance to further understanding the mechanism of miRNA response to salt stress.