植物特有蛋白FS4调控细胞内吞作用和植物对硼元素吸收转运的分子机制研究

细胞膜蛋白稳态的精确调控对于植物及时调整生长发育状态以应对复杂多变的外界环境至关重要。其中重要的科学问题是植物如何感应环境信号并选择性启动细胞膜蛋白的内吞、再循环或降解。为了深入探讨植物细胞膜蛋白内吞的调控机理，我们以植物硼元素通道蛋白BOR1-GFP为细胞膜标记蛋白，通过正向遗传筛选获得了影响细胞膜蛋白内吞降解的全新调控因子FS4。本项目拟从分子细胞、生化及遗传多个角度研究FS4基因表达模式和蛋白定位、FS4调控内吞作用和多泡体形成及多泡体介导的细胞膜蛋白分选的功能、FS4调控植物硼元素吸收转运的功能，重点研究FS4介导内吞作用及硼元素吸收转运的机理，最终阐明FS4调控植物细胞膜蛋白尤其是BOR1选择性内吞降解并影响植物硼元素吸收转运的分子机制。本研究将揭示植物细胞膜蛋白内吞降解的全新调控机制，并有助于我们深入理解植物对微量元素吸收转运的调控网络，为农作物的高效肥利用育种提供理论基础。

Tight control of plasma membrane (PM) protein homeostasis is crucial for plants to adjust the growth and development status and to adapt to the ever-changing environment. An important scientific question is how plants respond to environmental signals, and thereby selectively activate the endocytosis, recycling or degradation of PM proteins. In order to further investigate the regulatory mechanisms of endocytosis of plant PM proteins, we have used plant boron transporter BOR1-GFP as a PM marker protein to screen factors involved in endocytic degradation of plant PM proteins via a forward genetic approach. We have successfully obtained a novel regulatory factor FS4, which affects the endocytic degradation of BOR1-GFP. In this project, using a combination of molecular, cellular, biochemical and genetic approaches, we aim to study the expression profiles of FS4 gene and the dynamic subcellular localizations of FS4 protein; the functions of FS4 in the regulation of endocytosis, the multivesicular body (MVB) formation and the MVB-mediated PM protein sorting; the regulatory role of FS4 in the boron absorption and transport in plants. We will focus on characterizing the regulatory roles of FS4 in plant endocytic pathway as well as in plant boron absorption network, and will finally clarify the molecular mechanisms of FS4 functions in the regulation of endocytic degradation of plant PM proteins (especially BOR1) and in the modulation of plant boron absorption. This study will reveal the new regulatory mechanism of endocytic degradation of plant PM proteins, and will help us to further understand the regulatory network of uptake and transport of micronutrients in plants, and thereby provide the potential theoretical basis for crop breeding to improve the nutrient use efficiency.