miR169介导的逆境诱导植物早花的分子调控机制研究

This project will elucidate the role of miR169 in regulating flowering time. Timing of flowering is critical to plant reproductive success. The timing of floral induction is controlled by sophisticated regulatory networks that monitor changes in the environment. Plants can be induced to flower under stress conditions. MiR169 is up-regulated in environmental stress responses. In previous study, we demonstrate that miR169 family members are up-regulated in Arabidopsis, maize and soybean under abiotic stresses. Over-expression of miR169d results in early flowering in Arabidopsis. We hypothesis that miR169d is involved in stress-induced early flowering in Arabidopsis thaliana. This project aims to understand how miR169 regulate flowering time. The project centers on targets of miR169d NF-YA2 and NF-YA10, which will be isolated and a series of plant expression vectors related to targets of miR169d will be constructed, which then will be and transformed to Arabidopsis. Flowering time of transgenic Arabidopsis plants will be studied as a control of wild-type. The project will employ genetic, molecular, cell, and genomic approaches to identify key role of miR169d/NF-YA2 (10) in stress-induced flowering. This project will put forward a new flowering pathway and will have a update on theory of flowering network of Arabidopsis.The research works will be benefit to crop breedind for stress tolerance.

开花是植物个体发育和后代繁衍的中心环节，受外界环境和内部信号的精确调控，植物在逆境条件下会提前开花。本课题组前期研究表明，miR169逆境响应上调表达是一种普遍现象，同时ath-miR169d过表达的拟南芥植株表现为开花提前，推测miR169d参与了逆境诱导的开花过程。本项目拟在前期工作基础之上，构建一系列ath-miR169d靶基因的过表达载体，转化拟南芥，研究靶基因参与开花调控的生理功能；利用基因芯片和qRT-PCR筛选各转基因株系中差异表达的开花相关基因，采用CHIP、烟草叶片瞬时表达和EMSA实验鉴定受miR169d直接调控的下游基因，阐明miR169d介导调控的开花途径的分子机制；解析该途径与其他6条开花途径的关系，提出一条新的由miR169介导的逆境诱导开花的调控途径。对完善植物开花调控网络具有重要理论价值，并为生产中耐逆境分子育种提供理论依据。

开花是植物个体发育和后代繁衍的中心环节，受外界环境和内部信号的精确调控，叶片则作为光合作用的器官，对于植物的发育和生物量的积累至关重要。植物在逆境条件下会提前开花，miR169逆境响应上调表达是一种普遍现象，同时miR169d过表达的拟南芥植株表现为开花提前和莲座叶减少变小，推测miR169d参与了逆境诱导的开花和莲座叶的发育过程。在前期工作基础之上，本项目首先鉴定了miR169d的靶基因为NF-YA2和NF-YA10，构建系列NF-YA2和NF-YA10的过表达载体，获得不同转基因株系，以此为材料分别从生理、遗传、细胞、分子、组学等角度对miR169d/NF-YA2(10)模块介导逆境诱导早花和叶片发育的分子调控机制进行阐明，研究结果表明：（1)过表达NF-YA2开花延迟，与miR169d 过表达株系表型相反，在逆境条件下，miR169d响应逆境上调表达，降解其靶基因NF-YA2，从而减弱NF-YA2对开花抑制因子FLC的正调控，进一步释放被FLC抑制的下游靶基因FT和LFY的表达，引起开花。这一条新的开花调控途径，首次揭示了干旱等逆境导致植物早花的分子调控机制，对完善植物开花调控网络具有重要理论价值，并为生产中耐逆境分子育种提供理论依据。（2)NF-YA2和NF-YA10过表达拟南芥株系的莲座叶较野生型多，叶片大，且叶片表皮细胞也大，均与miR169d 过表达株系表型相反，且在抽薹和种子成熟之后还持续长出新叶；miR169d，NF-YA2和NF-YA10主要在顶端分生组织（SAM）和叶片维管系统中表达，进一步研究发现NF-YA2和NF-YA10通过对IAA合成途径基因YUC2的作用，介导生长素信号途径参与了拟南芥叶原基的起始和叶片发育的调控，研究结果可以为增强叶菜类植物的光合效率以及增加生物量和提高作物产量提供理论依据。