条锈菌效应子Pst30抑制植物的胼胝质和活性氧积累

 条形柄锈菌小麦专化型(Puccinia striiformis f. sp. tritici,Pst)导致的小麦条锈病严重威胁着我国的小麦生产安全。解析病菌的致病机理,对开发病害防控技术与策略具有重要的指导意义。研究发现效应子是病菌重要的致病因子,揭示效应子调控寄主免疫机制可加深对病菌的认知。本课题组前期在全基因组筛选条锈菌效应子中获得了一个候选效应子基因Pst30,该基因所编码的蛋白N-端含有分泌肽,无明显功能结构域。qRT-PCR分析显示Pst30在条锈菌侵染小麦后12 h诱导表达,72 h诱导表达至高峰。利用农杆菌侵染在烟草中瞬时表达Pst30^ΔSP-GFP融合蛋白,发现Pst30^ΔSP定位在细胞质。在烟草中瞬时表达该效应子能够显著抑制Bax诱导的细胞坏死。利用细菌的Ⅲ型分泌系统在小麦中瞬时表达Pst30,能够抑制荧光假单胞杆菌引起的胼胝质积累,导致由无毒性条锈菌小种CYR23引起的小麦过敏性坏死面积和活性氧积累减少,菌丝面积和长度增加。推测小麦条锈菌效应子Pst30可抑制寄主植物的PTI(PAMP-triggered immunity, PTI)和ETI(Effectors-triggered immunity, ETI),促进自身的侵染。

Effector Pst30 from Puccinia striiformis f. sp. tritici inhibits callose deposition and ROS accumulation in plant

Wheat stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) seriously threatens the wheat production in our country. Therefore, to elucidate mechanism of pathogenesis is crucial to develpoment of effective disease control techniques and strategies. Pathogens are known to have secreted effectors as virulence factors and to dissect the molecular basis of regulating host immunity system is benefit for understanding the pathogensis. In our previous screening for the candidate genes encoding secreted proteins, we obtained a highly expressed gene Pst30 which encodes a protein without obvious functional domain except a signal peptide in N-terminus. qRT-PCR analysis showed that Pst30 was induced in wheat at 12 h after infection and reached the peak at 72 h; The agroinfiltration-based transient expression of Pst30^ΔSP-GFP fusion protein in tobacco, demonstrate that Pst30 localizes in the cytoplasm; This protein also could inhibit Bax-induced cell death in tobacco. Transiently expressing Pst30 in wheat via the Type Ⅲ secretion system, inhibited not only the deposition of callose caused by Pseudomonas fluorescens but also reduced the necrotic area and reactive oxygen species accumulation caused by the avirulent Pst pathotype CYR23, which resulted in the hyphal area and length increased. Taken together, it is proposed that Pst30 inhibited PAMP-triggered immunity (PTI) and Effectors-triggered immunity (ETI) of host plants to promote infection.