microRNA(miRNA)通过调节靶基因的表达影响植物生长发育和对逆境的响应。阐明它们的功能对水稻遗传育种具有重要意义。Osa-miR1848是从谷穗中鉴定的一个目前只在水稻中发现的miRNA。我们已有的研究显示Osa-miR1848通过参与调节油菜素内酯(Brassinosteroid, BRs)和蜡质(Wax)的合成，影响了植株的株高、结实和耐逆性。本项目拟应用形态学、分子生物学、生理生化技术等研究：(1)Osa-miR1848和靶基因互作的机制(如：Osa-miR1848与靶基因mRNA结合与降解的分子证据，它们在时间和空间上的表达是否重叠)；(2)Osa-miR1848调节BR和腊质合成的分子机制；(3)Osa-miR1848调控株高、结实及在逆境响应中的作用机制。研究将阐明Osa-miR1848的生物学功能，加深对BR和蜡质合成调节的理解，并评价其在水稻分子育种中的应用价值。

Rice is one of the most important staple crops in the world. The development of rice is controlled by many factors. MicroRNAs (miRNAs) are short RNAs found in eukaryotic cells, and are transcriptional and post-transcriptional regulators that bind to complementary sequences on target mRNAs, usually resulting in translational repression or target degradation. MiRNAs are involved in the regulation of plant growth and development, and show response to biotic and abiotic stresses. Elucidation of the function of miRNAs is important for genetics and molecular breeding of rice. The miRNA,Osa-miR1848, was first isolated from the filling grain of rice by Zhu et al (2008). To our knowledge, a systematic study of the function of Osa-miR1848 in rice has not been reported yet. In our preliminary study, we found that: (1) Osa-miR1848 regulates the expression of two key genes in the biosynthetic pathway of brassinosteroid and wax in rice. (2) Compared to the control, the transgenic rice that overexpressed Osa-miR1848 show less tolerance to some biotic and abiotic stresses,such as drought, cold, salt treatments,aphid and shealth rot, and have some specific phenotypes including lower seed setting rate, shorter seeds and plant height. This project proposal that developed based on our preliminary results aims to study:(1) the interaction between Osa-miR1848 and mRNAs of its target genes, e.g., the molecular mechanism of binding and target degradation; and the possible interaction pattern during the spatial and temporal expression;(2)the regulation mechanism of Osa-miR1848 in the biosynthetic pathway of brassinosteroid and wax;(3)the function of Osa-miR1848 during the growth and development and the response to abiotic and biotic stresses in rice. This project will be helpful to understand the functions of Osa-miR1848 and biosynthetic pathways of brassinosteroid and wax in plants，and will also provide a clue for investigation of signal transduction mechanism of BR in the regulation of plant growth and development,and give a evaluation for its application value in rice molecular breeding.