Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech, 78026 Versailles, France.
Curr Biol. 2011 Oct 25;21(20):1720-6. doi: 10.1016/j.cub.2011.08.057. Epub 2011 Oct 6.
Tissue mechanics have been shown to play a key role in the regulation of morphogenesis in animals [1-4] and may have an equally important role in plants [5-9]. The aerial organs of plants are formed at the shoot apical meristem following a specific phyllotactic pattern [10]. The initiation of an organ from the meristem requires a highly localized irreversible surface deformation, which depends on the demethylesterification of cell wall pectins [11]. Here, we used atomic force microscopy (AFM) to investigate whether these chemical changes lead to changes in tissue mechanics. By mapping the viscoelasticity and elasticity in living meristems, we observed increases in tissue elasticity, correlated with pectin demethylesterification, in primordia and at the site of incipient organs. Measurements of tissue elasticity at various depths showed that, at the site of incipient primordia, the first increases occurred in subepidermal tissues. The results support the following causal sequence of events: (1) demethylesterification of pectin is triggered in subepidermal tissue layers, (2) this contributes to an increase in elasticity of these layers-the first observable mechanical event in organ initiation, and (3) the process propagates to the epidermis during the outgrowth of the organ.
组织力学在动物形态发生的调控中起着关键作用[1-4]，在植物中可能也具有同样重要的作用[5-9]。植物的气生器官是在茎尖分生组织中按照特定的叶序模式形成的[10]。分生组织起始一个器官需要高度局部的不可逆表面变形，这取决于细胞壁果胶的去甲酯化[11]。在这里，我们使用原子力显微镜（AFM）来研究这些化学变化是否会导致组织力学的变化。通过绘制活分生组织的粘弹性和弹性图，我们观察到在原基和初生器官部位，与果胶去甲酯化相关的组织弹性增加。在不同深度测量组织弹性表明，在初生原基部位，最初的增加发生在表皮组织中。这些结果支持以下因果事件序列：（1）果胶的去甲酯化在表皮组织层中被触发，（2）这导致这些层的弹性增加——是器官起始的第一个可观察到的机械事件，（3）在器官生长过程中，该过程传播到表皮。
