MOLECULAR ANALYSIS OF PLANT ORGAN AND TISSUE DEVELOPMENT

本研究分为两个项目。器官分离和茎分生组织形成我在拟南芥中分离到CUC突变体，它的幼苗融合了子叶，没有茎顶端分生组织。该突变体是由CUCI和CUC2基因双突变引起的，并克隆了CUC2基因。在本研究中，我们明确了以下4点。(1)CUC基因是启动STM表达形成顶端分生组织所必需的基因。(2)CUC2的空间表达需要STM才能完成子叶的分离。(3)CUC2在顶端分生组织与叶原基之间、花序分生组织与花分生组织之间以及花的各器官之间均有表达。(4)中子叶细胞是形成完整的雌蕊群和花中胚珠所必需的。拍摄向重力性；拍摄显示负向重力性。为了研究地上部向重力性的分子机制，我们从拟南芥中分离了许多向重力性降低的突变体，并确定了9个与地上部向重力性相关的新基因座，分别是SGR1-7、RHG和SLR。(1)编码bZIP型转录因子的SGR1和SGR7是下胚轴和花序茎中内胚层细胞分化所必需的，内胚层细胞是这些器官中的重力感受细胞。(2)SLR基因编码JAA-14基因，JAA-14是一种核蛋白，在生长素信号通路中起重要作用。(3)SGR2对新梢向重力性和胚胎发生均有重要作用。(4)sgr4在下胚轴和花序茎的内胚层细胞中的淀粉质定位和运动异常，导致向重力性降低。

This research is divided into two projects.1. Organ separation and shoot meristem formation I have isolated the cuc mutant in Arabidopsis thaliana, which seedlings have fused cotyledons and no shoot apical meristem. This mutant was caused by double mutations in CUCI and CUC2 genes and CUC2 genes was cloned. In this research, we made clear next 4 points. (1) The CUC genes were essential for initiation of STM expression to form shoot apical meristem. (2) STM was required for proper spatial expression of CUC2 at later stages to separate cotyledons. (3) CUC2 was expressed at boundaries between shoot apical meristem and leaf primordia, between inflorescence meristem and floral meristem, and among each organs of flowers. (4) CUCs were essential to form intact gynoecium and ovules in flowers.2. Shoot gravitropism ; Shoot shows negative gravitropism. To investigate molecular mechanisms of shoot gravitropism, we have isolated many reduced-gravitropic mutants from Arabidopsis thaliana and identified 9 new loci relating to shoot gravitropism, SGRl-7, RHG and SLR.In this research, we made clear next 4 points. (1) The SGRl, which encodes bZIP type transcription factor, and SGR7 were essential for endoderm cell differentiation in hypocotyl and inflorescence stem and endoderm cells were gravity perception cells in these organs. (2) The SLR gene encodes JAA 14 gene, which was a nuclear protein and important in auxin signaling pathway. (3) SGR2 was important for both shoot gravitropism and embryogenesis. (4) sgr4 was abnormal in amyloplastlocalization and movement in endoderm cells of hypocotyl and inflorescence stems causing reduced gravitropism.