State Key Laboratory for Protein and Plant Gene Research, Peking-Yale Joint Research Center for Plant Molecular Genetics and AgroBiotechnology, College of Life Sciences, Peking University, Beijing, China.
J Integr Plant Biol. 2011 Jun;53(6):493-506. doi: 10.1111/j.1744-7909.2011.01054.x.
In plants, the meristem has to maintain a separate population of pluripotent cells that serve two main tasks, i.e., self-maintenance and organ initiation, which are separated spatially in meristem. Prior to our study, WUS and WUS-like WOX genes had been reported as essential for the development of the SAM. In this study, the consequences of gain of WOX1 function are described. Here we report the identification of an Arabidopsis gain-of-function mutant wox1-D, in which the expression level of the WOX1 (WUSCHEL HOMEOBOX 1) was elevated and subtle defects in meristem development were observed. The wox1-D mutant phenotype is dwarfed and slightly bushy, with a smaller shoot apex. The wox1-D mutant also produced small and dark green leaves, and exhibited a failure in anther dehiscence and male sterility. Molecular evidences showed that the transcription of the stem cell marker gene CLV3 was down-regulated in the meristem of wox1-D but accumulated in the other regions, i.e., in the root-hypocotyl junction and at the sites for lateral root initiation. The fact that the organ size and cell size in leaves of wox1-D are smaller than those in wild type suggests that cell expansion is possibly affected in order to have partially retarded the development of lateral organs, possibly through alteration of CLV3 expression pattern in the meristem. An S-adenosylmethionine decarboxylase (SAMDC) protein, SAMDC1, was found able to interact with WOX1 by yeast two-hybrid and pull-down assays in vitro. HPLC analysis revealed a significant reduction of polyamine content in wox1-D. Our results suggest that WOX1 plays an important role in meristem development in Arabidopsis, possibly via regulation of SAMDC activity and polyamine homeostasis, and/or by regulating CLV3 expression.
在植物中，茎尖分生组织必须维持一个独立的多能细胞群体，这些细胞主要有两个功能，即自我维持和器官起始，这两个功能在茎尖分生组织中是空间分离的。在我们的研究之前，已经报道 WUS 和 WUS 样 WOX 基因对于 SAM 的发育是必不可少的。在这项研究中，描述了 WOX1 功能获得的后果。在这里，我们报告了拟南芥功能获得突变体 wox1-D 的鉴定，其中 WOX1（WUSCHEL HOMEOBOX 1）的表达水平升高，并观察到分生组织发育的细微缺陷。wox1-D 突变体表现为矮小和略丛生，顶芽较小。wox1-D 突变体还产生小而深绿色的叶子，并表现出花药开裂失败和雄性不育。分子证据表明，干细胞标记基因 CLV3 的转录在 wox1-D 的分生组织中下调，但在其他区域（即根-下胚轴交界处和侧根起始部位）积累。wox1-D 叶片中叶器官大小和细胞大小小于野生型的事实表明，细胞扩展可能受到影响，以便部分延迟侧器官的发育，可能通过改变 CLV3 在分生组织中的表达模式。发现 S-腺苷甲硫氨酸脱羧酶（SAMDC）蛋白 SAMDC1 能够通过酵母双杂交和体外下拉测定与 WOX1 相互作用。HPLC 分析显示 wox1-D 中的多胺含量显著降低。我们的结果表明，WOX1 在拟南芥的分生组织发育中发挥重要作用，可能通过调节 SAMDC 活性和多胺稳态，和/或通过调节 CLV3 的表达。
