赖草地下根茎网梯级分蘖基因调控机理研究

Rhizomatous grass is one of the most important compositions in the grass population and community structure.On grassland many fine herbage are capable of producing subterranean rhizomes. By the way of tillering of rhizomes, which is also defined as clonal growth, the plants can reproduce in the form of vegetative propagation so as to form the interlaced rhizomes network and corresponding newly produced ramets. Leymus secalinus is typical clonal plant that can fulfill vegetative propagation through tillering. Our project aims to investigate the genetic regulation mechanism of Leymus secalinus tillering by cloning the genes in Leymus secalinus which is homolog to la gene which is the key gene regulating tiller angles in rice; Performing the tissue-specific and time-specific analyses of two key genes including cloned LRC1 (homologous gene of rice tillering origination and growth regulatory gene MOC1), combining with the phenotypic analysis of target gene over-expression and loss-of-expression lines. The development of this project will establish the foundation of monocotyledon tillering molecular regulation mechanism which is special to developmental biology, provide the key candidate genes to excavate and utilize the affluent germplasm gene group of our country, to recover and optimize grass ecosystem and to improve the crop variety as well.

根茎型禾草是草原牧草种群及群落结构的重要组成部分，很多优良牧草具有地下根茎，通过分蘖进行无性繁殖，从而形成纵横交错的地下根茎网及与之对应的地上子代分株。赖草是典型的无性繁殖植物，本项目拟通过同源基因克隆技术，克隆水稻分蘖角度调控关键基因la在赖草中的同源基因；并对包括已克隆的LRC1基因（是调控水稻分蘖起始、生长的MOC1基因在赖草中的同源基因）在内的2个关键基因进行与地下根茎网梯级分蘖发育进程同步的组织、时段特异性表达分析，结合生态因子调控下目标基因过量表达、缺失表达株系表型和生理因子检测分析，进而揭示赖草根茎网梯级分蘖与2个基因调控表达间关联机制。该机理的阐明，不仅对单子叶植物具有重要的发育生物学意义，同时也为充分利用根茎分蘖型禾草来恢复退化、沙化草地植被及禾谷类农作物分蘖性状改良提供实验证据；另外，该根茎分蘖基因调控机理的揭示也为顽固的根茎型农田杂害草防治和境外入侵种防控提供新思路。

天然草原约占我国土地面积的41%，无论在草甸草原、典型草原、荒漠化草原还是在高寒草甸，通过根茎进行分蘖增殖的根茎型禾草往往凭借其耐干旱、耐贫瘠、耐践踏等诸多优良性状而成为群落建群种和优势种。本项目以典型的根茎型禾草赖草为研究对象，通过同源基因克隆技术结合计算智能算法，克隆了赖草分蘖角度调控相关LA基因，其cDNA全长1606bp，编码416 氨基酸，分子量42.67kD，理论等电点4.69，含3个跨膜区；通过实时荧光定量PCR技术分析了LRC1基因在赖草幼苗（种子萌发出土后第4-8周）不定根和不定根发生部位的节中的表达量，结果表明：LRC1基因在赖草不定根中的表达量随着幼苗发育进程的推进而逐步增加，而在不定根发生部位的节中的表达量则呈现为先增后减、再增加的波动趋势；短光照处理对LRC1基因表达有抑制作用。LRC1基因组织特异性表达检测分析表明，其在根茎等地下部位表达量显著高于叶片、茎、花等地上部位；另外，原位杂交结果显示，该基因在赖草根茎节有丰富表达，尤其是在皮层细胞的细胞壁表达量较高。该项目为如何深入开展赖草等根茎型禾草分蘖过程的基因调控机理研究奠定了基础，特别是赖草幼苗如何分化产生第一条根茎基因调控研究发现了线索。