OsmiR530在phyB介导的光信号途径中的作用机制研究

MicroRNAs (miRNAs) and phytochrome B (phyB) play important roles in multiple processes, such as plant growth and development and defense responses. However, the mechanism of phyB-mediated light signaling is still unclear. Little information about the relationship between phyB and miRNAs has been reported so far. In our previous study, we found a miRNA, OsmiR530, was significantly up-regulated in the phyB mutant. Transgenic rice plants overexpressing OsmiR530 showed significantly reduced plant height, smaller seeds and less sensitivity to the red light, which are similar to those of phyB mutant. These results indicate that OsmiR530 participates in phyB-mediated light signaling. OsmiR530 belongs to a highly conserved miRNA family in plants, miR530 family. There is only one member of miR530 in rice genome. However, the regulation and biological roles of miR530 in plants are sill elusive. Based on the results from degradome sequencing and 5’ RLM-RACE, OsDE1 was identified as the target of OsmiR530. The function of OsDE1 is unknown. Analysis of cis-elements in OsMIR530 promoter regions reveals that it contains multiple phytochrome-interating factor (PIF) binding sites. Furthermore, the expression of OsmiR530 was significantly down-regulated in OsPIL15 and OsPIL16 overexpression transgenic plants, while its target gene OsDE1 was significantly up-regulated. These results indicate OsPIL15 and OsPIL16 are likely to act upstream of OsmiR530. Consistently, OsPIL15 was identified as direct regulator of OsMIR530 by ChIP assay. In this project, we plan to investigate functions of osa-miR530 and its target in phyB-mediated light signaling and identify the upstream regulators of OsMIR530. The expected results will establish a novel phytochrome signaling pathway (phyB-OsPIL15/16-OsmiR530-OsDE1) and lay an important foundation for rice yield and quality improvement.

miRNA和phyB在植物生长发育和胁迫响应等方面具有重要调控作用。目前对miRNA在phyB信号通路中的作用知之甚少。前期研究发现，OsmiR530在phyB突变体中表达显著提高，其过表达株系红光敏感性降低、株高降低、种子变小，与phyB突变体表型一致，推测其参与了phyB信号通路。miR530在水稻中只有一个成员且功能未知。通过降解组测序和5’RACE，确定其靶基因为未知基因OsDE1。MIR530启动子含有多个光敏色素作用因子PIF的结合位点，且PIL15/16的过表达导致OsmiR530表达显著降低，其靶基因表达显著提高，这暗示PIL15/16可能是OsmiR530上游基因。利用ChIP技术，验证了MIR530与PIL15的互作。本项目拟通过对OsmiR530及其靶基因的功能分析及上游基因鉴定，阐明其在phyB介导的信号途径中的作用机制，为水稻农艺性状改良提供新的理论依据和方法。

miRNA和phyB在植物生长发育和胁迫响应等方面具有重要调控作用。目前对miRNA在phyB信号通路中的作用知之甚少。前期研究发现，OsmiR530在phyB突变体中表达显著提高，其过表达株系红光敏感性降低、株高降低、种子变小，与phyB突变体表型一致，推测其参与了phyB信号通路。本研究通过对水稻OsmiR530及其靶基因OsPL3和上游光敏色素作用因子OsPIL15的研究，全面解析了其对水稻产量调控的作用机制。研究发现OsmiR530负调控了水稻产量。过表达OsmiR530显著降低籽粒大小和穗粒数，导致产量下降，而抑制OsmiR530的表达则会显著提高水稻产量。敲除OsmiR530的靶基因OsPL3后，会降低水稻产量。进一步研究表明，OsPIL15可以直接结合OsMIR530启动子中的G-box元件激活其表达。遗传变异分析表明，OsMIR530在水稻育种过程中可能经过了人工选择。该研究结果阐明了水稻“OsPIL15-OsmiR530-OsPL3”模块调控水稻产量性状的分子机制，为水稻和其他作物高产育种提供重要理论依据。此外，本研究鉴定了一个新的OsmiR530的靶基因OsRMT，且其同OsPL3一样也正向调控水稻籽粒大小，初步研究表明OsPL3/OsRMT可能协同参与了OsmiR530对水稻产量调控。

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