植物拟分生细胞调控器官大小的分子机理研究

Organ size is an important agronomic trait, and control of organ size is also a fundamental question in developmental biology. Meristemoid cells are dispersed in the leaf and other organs and have stem cell activity. Meristemoids have been known to generate a large amount of pavement cells (48% in leaves). However, how meristemoids determime organ size is almost unknown. Recently, we find that SOD3, an F-box protein that forms part of a SKP1/Cullin/F-box (SCF) E3 ubiquitin ligase complex, controls organ size by promoting the proliferation of meristemoid cells. SOD3 physically associates with transcriptional regulators PPD1/2 and KIX8/9 and targets them for degradation. The SOD3-PPD/KIX pathway provides us a good opportunity to discover novel mechanisms of organ size control in plants. To reveal novel genetic and molecular mechanisms of organ size control, we will identify other targets of SOD3 and understand the functions of its targets in meristemoid cell proliferation and organ size control, characterize other components in the SOD3 pathway and understand their roles in meristemoid cell proliferation and organ growth, and build up a genetic and molecular framework for SOD3-mediated control of meristmoid cell proliferation and organ size control. This study will make a breakthrough in plant organ size control.

植物器官大小是重要的产量性状，大小调控也是基本的发育生物学问题。在植物叶片等器官中分布着一些拟分生细胞，具有干细胞活性。据统计叶片中48%的pavement细胞来源于拟分生细胞，但其决定器官大小的机制并不清楚。我们发现拟南芥中F-box蛋白SOD3直接与转录调控因子PPD1/2(PEAPOD)和KIX8/9相互作用，并介导它们的降解，通过调控拟分生细胞增殖，决定器官大小。ppd1ppd2kix8kx9仅部分抑制sod3-1表型，表明SOD3还有其他底物。SOD3-PPD/KIX途径是目前唯一知道的通过拟分生细胞调控器官大小的遗传途径，为揭示器官大小调控的新机制提供了契机。本项目将鉴定SOD3的互作蛋白、其他底物以及SOD3调控途径的其他成员，研究其调控拟分生细胞增殖和器官大小的分子机制，建立以SOD3为中心的拟分生细胞调控器官大小的分子遗传网络。该研究有望在植物器官大小调控领域取得新突破。

植物器官大小是重要的产量性状，也是基本的发育生物学问题。在植物叶片等器官中分布着一些拟分生细胞，具有干细胞活性。据统计叶片中48%的pavement细胞来源于拟分生细胞，但其决定种子大小的机制并不清楚。在本项目的资助下，主要揭示了拟南芥中KIX-PPD-MYC通过抑制GIF1表达调控种子大小的分子机制。拟南芥KIXs、PPDs和GIF1基因在大豆、苜蓿、玉米和水稻中的同源基因具有调控种子大小的功能，有望应用这些基因提高作物产量。

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