氧固醇结合蛋白调控稻瘟菌致病力及营养生长的分子基础

氧固醇结合蛋（OSBPs）广泛存在于由酵母到人类的许多真核生物中，它们通过保守的结构域与类固醇等脂类分子结合，参与调控细胞的脂类代谢、囊泡及非囊泡运输以及信号传导等过程。真菌中OSBP可介导酵母出芽生殖与曲霉产孢及菌落的辐射生长。稻瘟菌含有6个OSBP基因，我们发现其中三个基因为菌丝生长及致病过程所必需。本研究将立足这一新发现，通过进一步分析突变体表型，确定稻瘟菌OSBP蛋白影响生长及侵染的具体环节；通过转录组与代谢组分析，明确OSBP调控基因表达与代谢的关键途径；通过研究OSBP的亚细胞定位，分离鉴定其结合底物及互作蛋白，解析它们行使功能的分子基础。本研究将为揭示稻瘟菌侵染致病及生长发育机制提供新的视角，为未来研发稻瘟病防控新策略提供重要依据。

Oxysterol-binding proteins (OSBP) are a class of proteins that widely exist in eukaryotic organisms ranging from yeast to humans. OSBPs bind small lipid molecules, including steroids, phosphatidylinositol-4-phosphate, and phosphatidylserine, through the conserved ligand-binding domain and have important roles in a range of cellular processes including lipid metabolism, vesicle and non-vesicle trafficking, and signal transduction. Up to date, the role of OSBPs in mediating plant-microbe interaction has not been revealed, although these proteins have been reported to mediate polar growth during the budding process in Saccharomyces cerevisiae, and colony radial growth and sporulation in Aspergillus nidulans. We have identified 6 OSBP genes from the rice blast fungus, and found that they have overlapping but diversified functions in modulation of fungal virulence and vegetative growth: OSBP1 and OSBP2 are collectively key for the fungus to cause disease in planta, whereas OSBP1 and OSBP3 are essential in combination to colony radial growth on the plate. Based on these observations, we propose to further characterize the biological phenotypes of double mutants deficient in both OSBP1 and OSBP2 genes, and OSBP1 and OSBP3 genes, thereby identifying the exact pathological and cellular aspects where the OSBPs are involved. We will use an approach integrating multidisciplinary methods and technology, including plant pathology, biochemistry, cellular biology, transcriptomic and metabolomic analyses, to unravel the molecular basis of OSBP-mediated biology. Findings from this study will provide new insight on the mechanism of regulation of virulence and polar growth in Maganaporthe oryzae, and shed new light on the development of novel strategies for the control of the rice blast disease in future.