Peaucelle Alexis, Louvet Romain, Johansen Jorunn N, Höfte Herman, Laufs Patrick, Pelloux Jérome, Mouille Grégory
Laboratoire de Biologie Cellulaire, Institut Jean-Pierre Bourgin, INRA Centre de Versailles-Grignon, Versailles, France.
Curr Biol. 2008 Dec 23;18(24):1943-8. doi: 10.1016/j.cub.2008.10.065.
Plant organs are produced from meristems in a characteristic pattern. This pattern, referred to as phyllotaxis, is thought to be generated by local gradients of an information molecule, auxin. Some studies propose a key role for the mechanical properties of the cell walls in the control of organ outgrowth. A major cell-wall component is the linear alpha-1-4-linked D-GalAp pectic polysaccharide homogalacturonan (HG), which plays a key role in cell-to-cell cohesion. HG is deposited in the cell wall in a highly (70%-80%) methyl-esterified form and is subsequently de-methyl-esterified by pectin methyl-esterases (PME, EC 3.1.1.11). PME activity is itself regulated by endogenous PME inhibitor (PMEI) proteins. PME action modulates cell-wall-matrix properties and plays a role in the control of cell growth. Here, we show that the formation of flower primordia in the Arabidopsis shoot apical meristem is accompanied by the de-methyl-esterification of pectic polysaccharides in the cell walls. In addition, experimental perturbation of the methyl-esterification status of pectins within the meristem dramatically alters the phyllotactic pattern. These results demonstrate that regulated de-methyl-esterification of pectins is a key event in the outgrowth of primordia and possibly also in phyllotactic patterning.
植物器官由分生组织以特定模式产生。这种模式称为叶序，被认为是由信息分子生长素的局部梯度产生的。一些研究提出细胞壁的机械特性在控制器官生长中起关键作用。细胞壁的主要成分是线性α-1-4连接的D-半乳糖醛酸果胶多糖同型半乳糖醛酸聚糖（HG），它在细胞间黏附中起关键作用。HG以高度（70%-80%）甲酯化的形式沉积在细胞壁中，随后被果胶甲酯酶（PME，EC 3.1.1.11）去甲酯化。PME活性本身受内源性PME抑制剂（PMEI）蛋白调节。PME的作用调节细胞壁基质特性并在控制细胞生长中起作用。在这里，我们表明拟南芥茎尖分生组织中花原基的形成伴随着细胞壁中果胶多糖的去甲酯化。此外，分生组织内果胶甲酯化状态的实验性扰动会显著改变叶序模式。这些结果表明，果胶的调控去甲酯化是原基生长以及可能在叶序模式形成中的关键事件。
