赖草根茎顶芽觅食生长方向性基因调控机理研究

Continuous tilling and lateral growth of rhizome, which give the rhizomatous grass unique capability of lateral expansion, similar to foraging walk "animal", determine the configuration, habitat development mode and resource utilization of clone strains of rhizomatous grass. They play an important role especially in degraded grassland, desert, sand dunes and other fragile ecological system. It is still to be revealed that the mechanism of the orientation growth of rhizome apical bud achieving the lateral "foraging migration" in rhizomatous grass. Leymus secalinus is a perennial grass with rhizomatousness, and the expression characteristic of the key regulation genes was investageted in this project, based on the cloning of these genes regulating rhizome growth orientation, by setting the habitat heterogeneity induced experiment and the passive diversion experiment confronted with block content by the rhizome. This project is expected to reveal the regulation mechanism of rhizome growth orientation of Leymus secalinus, through overexpression of the key genes and Yeast Two-hybrid System, combined with the analysis of dynamic distribution of hormone and expression of genes related with hormone during the diversion of rhizome apical bud. This study is not only important for the understanding of the Strategy of spatial expansion of clonal plants, but also provides the experimental evidences for the recovery of the degraded, desertification grassland vegetation by the rhizomatous grasses, and improvement of tiller in cereal cropping. In addition, this study also provide the insight of prevention of obstinate rhizome type harmful grass and foreign invasive species.

根茎的持续分化和横向延伸生长，赋予了根茎类禾草很强的水平拓展迁移能力和抗扰动能力，使其在退化草原、荒漠、沙丘等脆弱生态系统中担负着重要作用。决定根茎类禾草实现横向“觅食游走”的根茎顶芽生长方向性基因调控机理有待揭示。本项目拟以典型根茎类禾草赖草为研究对象，在克隆其根茎顶芽生长方向性调控关键基因基础上，通过设置生境异质性诱导实验和根茎顶芽在有阻挡物条件下的被动转向实验，明确关键基因调控表达特征；进行关键基因过表达、酵母双杂实验确认调控途径，结合根茎顶芽转向生长过程中的植物激素分布动态、以及激素关联基因表达综合分析，以期初步揭示赖草根茎顶芽“觅食”生长方向性基因调控机理。该机理的阐明，不仅有助于揭示根茎型禾草空间分株放置的思维和生态适应的逻辑，而且为充分利用根茎分蘖型禾草恢复退化、沙化草地植被及禾谷类农作物分蘖性状改良提供实验依据，也为顽固的根茎型农田杂害草防治和外来入侵种防控提供新思路。

赖草是根茎类多年生禾草，通过根茎的无性生殖进行克隆生长，具有很强的入侵性和抗扰动能力，根茎在一定程度上赋予了赖草类似于动物的觅食游走能力，因此根茎在赖草等根茎类禾草株系发育、生态适应中发挥着特殊作用。项目围绕根茎分化产生和向性生长影响因素进行研究，结果表明：（1）过高氮磷等营养处理和干旱交替处理会延缓赖草分蘖根茎的产生，还会降低赖草幼苗根延伸生长速度和侧根的发生数；（2）相比于8 h短光照，12 h长光照处理更有利于赖草幼苗根系发育和分蘖发生；（3）赖草横向、纵向生长根茎顶芽内源激素分析结果表明，纵向中IAA和GA3含量显著高于横向，而Me-JA和BR则横向显著高于纵向，ZR和ABA无显著性差异，暗示IAA、GA3、Me-JA和BR与根茎顶芽向性生长过程密切相关；（4）转录组差异表达基因筛选发现LsPIN1、LsPROG1、LsLRC1及LsLAZY1在纵向生长方向顶芽内表达量显著高于横向，通过进一步对激素调控密切相关的LsPIN1、LsLAZY1进行亚细胞定位分析显示，LsLAZY1定位于细胞核，LsPIN1定位于细胞膜；（5）过表达LsPIN1和LsLAZY1转基因拟南芥株系、以及外源施加GA3、IAA诱导过表达转基因拟南芥根系表型分析发现，LsPIN1、LsLAZY1参与调控主根和侧根的发生和根系形态建成；（6）过表达LsPIN1和LsLAZY1转基因拟南芥根系重力诱导实验、回转器模拟微重力诱导实验均表明，LsPIN1和LsLAZY1参与了根的向重力性生长过程；（7）LsPIN1、LsLAZY1过表达转基因拟南芥根系生长素积累实验表明，LsPIN1、LsLAZY1的异位表达调控了拟南芥根系生长素的积累。以上结果表明，赖草根茎分化产生受到环境养分水平、内源激素含量、激素运输与累积的影响，异位表达实验结果表明LsPIN1和LsLAZY1基因在赖草根茎顶芽重力响应、生长方向性调控过程中起关键作用。本项目从分子水平深入挖掘根茎分化和取向生长相关基因，为探明赖草根茎分化产生和向性生长的分子机理提供重要理论依据。