Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, 113-8657, Japan.
Planta. 2012 May;235(5):1081-9. doi: 10.1007/s00425-012-1639-5. Epub 2012 Apr 5.
Rice PLASTOCHRON 1 (PLA1) and PLA2 genes regulate leaf maturation and plastochron, and their loss-of-function mutants exhibit small organs and rapid leaf emergence. They encode a cytochrome P450 protein CYP78A11 and an RNA-binding protein, respectively. Their homologs in Arabidopsis and maize are also associated with plant development/organ size. Despite the importance of PLA genes in plant development, their molecular functions remain unknown. Here, we investigated how PLA1 and PLA2 genes are related to phytohormones. We found that gibberellin (GA) is the major phytohormone that promotes PLA1 and PLA2 expression. GA induced PLA1 and PLA2 expression, and conversely the GA-inhibitor uniconazole suppressed PLA1 and PLA2 expression. In pla1-4 and pla2-1 seedlings, expression levels of GA biosynthesis genes and the signal transduction gene were similar to those in wild-type seedlings. GA treatment slightly down-regulated the GA biosynthesis gene GA20ox2 and up-regulated the GA-catabolizing gene GA2ox4, whereas the GA biosynthesis inhibitor uniconazole up-regulated GA20ox2 and down-regulated GA2ox4 both in wild-type and pla mutants, suggesting that the GA feedback mechanism is not impaired in pla1 and pla2. To reveal how GA signal transduction affects the expression of PLA1 and PLA2, PLA expression in GA-signaling mutants was examined. In GA-insensitive mutant, gid1 and less-sensitive mutant, Slr1-d1, PLA1 and PLA2 expression was down-regulated. On the other hand, the expression levels of PLA1 and PLA2 were highly enhanced in a GA-constitutive-active mutant, slr1-1, causing ectopic overexpression. These results indicate that both PLA1 and PLA2 act downstream of the GA signal transduction pathway to regulate leaf development.
水稻 PLASTOCHRON 1（PLA1）和 PLA2 基因调节叶片成熟和叶龄，其功能丧失突变体表现出小器官和快速叶片出现。它们分别编码细胞色素 P450 蛋白 CYP78A11 和 RNA 结合蛋白。拟南芥和玉米中的同源物也与植物发育/器官大小有关。尽管 PLA 基因在植物发育中很重要，但它们的分子功能仍不清楚。在这里，我们研究了 PLA1 和 PLA2 基因与植物激素的关系。我们发现赤霉素（GA）是促进 PLA1 和 PLA2 表达的主要植物激素。GA 诱导 PLA1 和 PLA2 的表达，而 GA 抑制剂 uniconazole 则抑制 PLA1 和 PLA2 的表达。在 pla1-4 和 pla2-1 幼苗中，GA 生物合成基因和信号转导基因的表达水平与野生型幼苗相似。GA 处理轻微下调 GA 生物合成基因 GA20ox2，上调 GA 分解代谢基因 GA2ox4，而 GA 生物合成抑制剂 uniconazole 上调野生型和 pla 突变体中的 GA20ox2，下调 GA2ox4，表明 GA 反馈机制在 pla1 和 pla2 中没有受损。为了揭示 GA 信号转导如何影响 PLA1 和 PLA2 的表达，我们研究了 GA 信号转导突变体中 PLA 的表达。在 GA 不敏感突变体 gid1 和敏感性降低突变体 Slr1-d1 中，PLA1 和 PLA2 的表达下调。另一方面，在 GA 组成型激活突变体 slr1-1 中，PLA1 和 PLA2 的表达水平高度增强，导致异位过表达。这些结果表明，PLA1 和 PLA2 都作用于 GA 信号转导途径的下游，以调节叶片发育。
