MicroRNA对UV-B胁迫下水稻叶片光合功能变化的调控

Enhanced UV-B radiation leads to a decline in photosynthetic capacity，leaf senescence，and yield in rice. However， we still do not understand the molecular regulation mechanism of the responses of rice under UV-B stress. In our early research，we identified proteins in rice leaf in response to UV-B stress through proteomic analysis. We discovered two proteins in rice chloroplast (Plantacyanin and Cu/Zn SOD) that are clearly down-regulated under UV-B stress. miRNA which controls these two gene express, is predicted to be induced by UV-B radiation. This suggests that plant can regulate miRNA and adjust UV-B stress through miRNA pathway. Using physiology, molecular cloning and bioinformatics methods, this project will identify miRNAs induced by UV-B radiation. The focus is to elucidate the function of miR408 and miR398, which are predicted in the control of photosynthetic efficiency，and their target genes. We will construct plasmids, establish transgenic plants, analyze the expression level of target gene transcription and its downstream physiological and biochemical reactions in transgenic plants. The above results will contribute to further elucidate the molecular mechanism of rice response to UV-B stress and provide a theoretical guidance for breed improvement and germplasm enhancement.

增强UV-B辐射导致水稻光合能力下降、叶片早衰、产量下降，然而我们对其响应UV-B胁迫的分子机理尚不清楚。前期研究中我们通过蛋白组学方法鉴定了水稻叶片中UV-B响应的蛋白，发现叶绿体中有2个蛋白(plantacyanin和Cu/Zn SOD)在UV-B胁迫下显著下调。参与调控这2个基因表达的miRNA (miR408、miR398)则受到UV-B诱导，暗示UV-B可能通过miRNA途径参与调控植物对UV-B的响应。本项目研究拟通过生理学、分子生物学和生物信息学等方法，鉴定水稻中对UV-B响应的miRNA, 重点探明可能参与调控光合作用效率的miR408和miR398及其靶基因；构建miRNA和靶基因的表达载体，获得水稻转化植株；分析转化植株中靶基因表达水平，以及对下游生理生化反应的调控机制。上述结果将进一步阐明水稻响应UV-B胁迫的分子机制，也为作物品种改良和种质创新提供理论依据和借鉴。

增强 UV-B 辐射导致水稻光合作用下降、叶片早衰、产量下降，目前植物响应 UV-B 胁迫的分子机理尚不清楚。本项目研究通过生理学、分子生物学和生物信息学等方法，分离鉴定了水稻中对 UV-B 响应的 miRNA，重点研究了 miR408 和 miR398 及其靶基因；构建 miRNA 和靶基因的表达载体，获得水稻和拟南芥转化植株； 分析转化植株中靶基因表达水平，以及对下游生理生化反应的调控机制；并探讨了He-Ne激光减轻增强UV-B辐照造成植物损伤、早衰的机理。研究结果如下： (1) UV-B对水稻光合作用效率影响的生理机理，研究表明：增强UV-B胁迫下，在整个生育期，水稻叶绿素含量呈下降趋势；全电子传递活性、PSⅡ和PSⅠ电子传递活性、光合磷酸化水平均呈先升高后下降的趋势，叶绿素荧光参数也呈下降趋势；（2）增强UV-B胁迫下，随着辐射强度增加、时间增长，miR408、miR398基因表达水平进一步提高；（3）增强UV-B辐射下，过表达miR408、miR398植株生长矮小，叶面积减小，叶绿素含量降低，荧光参数Fv/Fm降低，淬灭参数qN升高，原初光能转化效率降低，抗氧化酶系统也发生了变化，表现为酶含量下降，过氧化产物增多。与野生型水稻相比，UV-B辐射下过表达了miR408的水稻酶活力下降趋势更严重，表明miR408在响应植物对抗UV-B辐射的过程中提高了其表达量，致使抗氧化酶系统无法修复；(4) UV-B辐射下，沉默miR408、miR398的植株生长良好，光合作用强于野生型植株；（5）UV-B辐射下，miR398的靶基因CSD、miR408靶基因plantacyanin表达下降，酶活性降低，电子传递活性下降，光合作用减弱，从而使植株抗UV-B能力下降； (6)He-Ne激光对增强UV-B辐射造成植株的损伤有一定修复作用，表现为提高了UV-B辐射下水稻剑叶的光合作用和抗氧化能力。研究结果将进一步阐明植物响应 UV-B 胁迫的分子机制，也为作物品种改良和种质创新提供理论依据和借鉴。