形态建成是植物生长发育的关键环节,它包括不可分割的暗形态建成和光形态建成两个相联阶段。正常的暗形态建成必需要保持活跃的油菜素内酯（BR）信号而由暗形态建成向光形态建成的转变必需抑制BR信号。前人研究认为BR信号只来自质膜BR受体蛋白（PM-BRI1）。但我们的前期研究发现，拟南芥野生型BRI1拥有PM-BRI1和内质网受体蛋白（ER-BRI1）。我们还发现提高没有PM-BRI1的bri1突变体的ER-BRI1水平可完全恢复暗形态建成但只能部分恢复光形态建成。这表明光形态建成需要ER-BRI1和PM-BRI1而暗光形态建则只需要ER-BRI1。本课题拟进一步阐明ER-BRI1的生物学功能和它存在的必要性。同时我们研究PM-BRI1和ER-BRI1在协调控制植物的光形态建成尤其是叶子大小和形状形成中的细胞及分子机制。本研究可为阐明BR的生物学作用机制及全面认识植物形态建成机理奠定良好基础。

Morphogenesis is one of the most important processes during plant growth and development and it includes two closely related consective steps: skotomorphogenesis and photomorphogenesis. Normal skotomorphogenesis requires active Brassinosteroid (BR) signaling although the transition from skotomorphogenesis to photomorphogenesis requires the plants to inhibit BR signaling by lights. Prior to this study, BR signaling has been considered only initiating through the plasma membrane BR receptor (PM-BRI1). However, our preliminary results show that there were PM-BRI1 and endoplasmic reticulum (ER) BR receptor (ER-BRI1) in wild-type Arabidopsis BRI1. In addition, we have found that increase of ER-BRI1 amount in a bri1 mutant without PM-BRI1 completely rescued the skotomorphogenesis but only partially rescued photomorphogenesis of this mutant. This indicates that the ER-BRI1 is required for skotomorphogenesis and both ER-BRI1 and PM-BRI1 are required for photomorphogenesis. Building from our preliminary study, our research will aim to apply molecular, biochemical, cellular and genetic approaches to further understand the biological function and necessity of having ER-BRI1 in plants. At the meantime, we will address how PM-BRI1 and ER-BRI1 coordinate with each other to regulate photomorphogenesis, especially the size and shape of leaves to understand their underlying cellular and molecular mechanisms. This study will enhance our understanding of BR signaling transduction pathway and the mechanisms by which it regulates plant biological functions. Our research will lay a solid foundation for full understanding of plant morphogenesis.