植物茎分枝的分子调控

植物茎分枝结构决定了不同植物的不同形态结构.本文从腋生分生组织的发生、腋芽的生长两个方面综述了近年来植物分枝发生发育相关的分子机理研究及其进展.发现在不同植物中腋分生组织形成的基本机制是相似的，LS（lateral suppressor）及其同源基因在不同植物中都参与腋生分生组织的形成，而BL(blind)及其同源基因也参与调控腋生分生组织的形成.腋生分生组织的形成可能也是受激素调控的.目前，对腋芽生长的分子调控机制的认识主要集中于生长素通过二级信使的作用调控腋芽的生长.而生长素调控腋芽生长的机制已经较为清楚的有两条途径：一是生长素通过抑制细胞分裂素合成来调控腋芽的生长；另一途径是一种类胡萝卜素衍生的信号物质参与生长素的运输调控(MAX途径)来调控腋芽的生长.最新研究表明,TB1的拟南芥同源基因在MAX途径的下游负调控腋芽的生长.此外，增强表达OsNAC2也促进腋芽的生长.

Molecular Mechanism of Shoot Branching in Plants

The diversified architecture of plants is determined primarily by the pattern of shoot branching.This review will present the research progresses in plant shoot branching from two aspects:the initiation of auxiliary meristem and the outgrowth of auxiliary buds.The basic mechanism controlling the initiation of auxiliary meristem was indicated to be conserved among different plant species.The LS(lateral suppressor)and its homologs regulated the initiation of auxiliary meristem in various plants,the BL(blind)and its homologs were known to be involved,and plant hormones were reported to regulate this process.Up to date,the knowledge about the outgrowth of auxiliary buds was derived from the studies of auxin regulated pathways,which included the repression of cytokinin synthesis by auxin signaling and the regulation of auxin transportation by the MAX pathway as the two most characterized ones.Recent reports have shown that arabidopsis homolog of TB1 acted as a tiller bud inhibitor downstream of MAX pathway,and the overexpression of OsNAC2 was able to promote tiller bud outgrowth.