调控叶片厚壁细胞发育的RCD1基因功能解析

Leaf shape has long been considered an important agronomic trait in rice. Moderate leaf rolling in rice leads to erect leaf canopies and higher photosynthetic efficiency, thus increasing grain yield. The sclerenchyma cell is one of the important vascular bundles organs and plays an important role in maintaining the leaf shape, structure and development. However, molecular mechanism controlling the sclerenchyma cell development is poorly understood. To address this question, we systematically screen the rice T-DNA tagged mutant library, a sclerenchyma cells defect mutant (scd1) was identified. Histological analysis in scd1 showed that sclerenchyma cells were defect in the small vascular bundles on the leaf blade. The corresponding place was occupied by a large number of mesophyll cells, leading to mechanical strength change. We isolated this gene by positional cloning, which encoded one of the radical-induced cell death families (RCD1) with unknown function. Using yeast two-hybrid technology, OSH15 gene was found to interact with RCD1. In the present study, molecular biology, biochemistry and genetics approaches.will be employed to further uncover the molecular mechanism of RCD1 in regulating leaf sclerenchyma cell development, including identification of downstream targets and interaction partners of RCD1 during sclerenchyma cell development.

叶片是植物光合作用主要场所，优良的叶片形态有利于塑造理想的株型，提高光合效率。厚壁组织是维管束的重要器官之一，在维持叶片形状、构造、发育等方面起着十分重要的作用，但目前对厚壁组织形成的分子机理知之甚少。课题组通过前期筛选，获得厚壁组织发育异常突变体scd1（sclerenchyma cell defect1），并利用图位克隆法获得了该基因，该基因编码Radical-induced Cell Death家族一员(RCD1)，并成功进行功能互补。同时筛选获得与RCD1基因互作基因OSH15。为了进一步研究RCD1基因在水稻叶片厚壁细胞形成中的作用机理，本项目拟以突变体scd1为材料，通过细胞生物学、分子遗传学等手段分析RCD1基因的生物学功能，研究RCD1、OSH15相互作用及调控的靶基因，从分子水平上揭示RCD1基因在厚壁细胞分化等方面的作用，进一步完善水稻叶片形态建成的调控

叶片是植物光合作用主要场所，优良的叶片形态有利于塑造理想的株型，提高光合效率。厚壁组织是维管束的重要器官之一，在维持叶片形状、构造、发育等方面起着十分重要的作用，但目前对厚壁组织形成的分子机理知之甚少。课题组通过前期筛选，获得一份叶片扭曲突变体twi1（twisted-leaf1），在本项目的支持下，开展了细胞学和分子遗传等相关试验。通过细胞学试验揭示了突变体twi1叶中厚壁组织发育异常是造成叶片扭曲的成因，并利用图位克隆法获得了基因TWI1，该基因编码 Radical-induced Cell Death 家族一员(RCD1)，并成功进行功能互补。利用酵母双杂交试验，筛选到与之相互作用的KNOX家族蛋白OSH15，KNOX家族蛋白在叶脉的形成及发育过程中发挥重要作用。通过多种手段（烟草2A系统、拟南芥叶毛互补），证明转录因子OSH15可以通过胞间连丝在细胞间穿梭移动，TWI1调控OSH15蛋白的移动；同时利用双突变体及免疫组化技术对OSH15蛋白在突变体内细胞水平的移动进行跟踪监测，发现twi1突变体中OSH15蛋白具有明显移动扩散，OSH15蛋白的移动导致维管束各细胞的异常，从而影响水稻叶脉的发生与发育。