OsEIL1调控水稻幼苗冠根起始的分子机制

Root systems of higher plants play essential roles in absorbing water and nutrients and supporting the plant body. Improved root architecture is crucial for productivity and stress resistance. In rice, crown roots are the major root type and are initiated at lower stem nodes as part of normal plant development. However, the regulatory mechanism of crown root development is poorly understood. During rice root morphogenesis, several developmental stages can be clearly distinguished, including crown root initiation, emergence, and elongation. Previous researches indicate that ethylene, a significant phytohormone in plant stress responses, plays an important role in the regulation of plant growth and development. Especially, we previously found that OsEIL1, a core transcription factor in ethylene signaling pathway, is the key regulator in ethylene-induced crown root initiation in rice. Analysis of transcriptome expression profiling showed that OsWOX11, which have been identified and characterized to function in the regulation of crown root initiation, was down regulated in oseil1, indicating that OsEIL1 regulates crown root initiation through transcriptional activation of OsWOX11. Based on the above studies, we will further conduct the following investigations in the proposed project. Firstly, we will analyze the function of OsWOX11 in ethylene-induced crown root initiation using oswox11 mutant and overexpression lines. And then we will analyze the genetic regulatory basis between OsEIL1 and OsWOX11 using oswox11oseil1 double mutant. Next we will verify the interaction domains of OsEIL1 and the key cis-elements in OsWOX11 promoter, to elucidate the molecular mechanism of transcriptional regulation of OsEIL1 in ethylene-induced crown root initiation, and finally we will analyze the effect of ethylene on OsEIL1 regulation of OsWOX11. Our study provide a new insight into understanding of ethylene in regulating rice crown root development, and will benefit the root architecture improvement in agriculture.

冠根作为水稻根系的主要组成部分，在水稻的生长发育及抗逆性中发挥着重要的作用。但其发生的调控机制并不清楚。前期研究发现，植物激素乙烯通过其信号分子OsEIL1促进水稻幼苗冠根的起始；通过对oseil1突变体转录组数据的分析，发现OsEIL1可能通过转录调控冠根起始关键调控基因OsWOX11来调控冠根的起始。本研究拟在以上研究基础上，利用oswox11突变体和过表达材料分析OsWOX11在乙烯调控水稻幼苗冠根起始中的功能；通过创建oswox11oseil1、oseil1OsWOX11-OX和oswox11OsEIL1-OX材料分析OsWOX11与OsEIL1的遗传调控关系；进一步鉴定OsEIL1与OsWOX11基因启动子顺式作用元件互作的核心元件位点，剖析OsEIL1转录调控OsWOX11基因表达的生化基础；阐明乙烯调控水稻幼苗冠根起始的分子机制，为水稻根系改良提供理论基础。

本项目的研究目标是通过鉴定OsEIL1与水稻冠根发育关键基因OsWOX11互作的生化和遗传基础，剖析OsEIL1介导乙烯调控水稻冠根发育的分子途径。通过3年的实施，我们圆满地完成了预期的研究内容。乙烯作为一种气体植物激素，在植物生长发育和逆境胁迫应答中发挥重要作用。已有研究表明，乙烯能够促进不定根的发育，但具体的分子机制还不清楚。本研究发现乙烯信号途径核心转录因子OsEIL1可以直接结合到水稻冠根发育关键基因OsWOX11的启动子上来激活其表达，从而促进冠根原基的起始。遗传分析表明OsEIL1上位于OsWOX11来调控冠根的发育。进一步的研究发现土壤紧实度促进了OsEIL1蛋白在根中的积累和冠根的发育。本研究解析了乙烯调控水稻冠根发育的分子机理，为水稻根系改良提供了新的途径和有用的基因。