R-SNARE Homolog MoSec22 Is Required for Conidiogenesis, Cell Wall Integrity, and Pathogenesis of <em>Magnaporthe oryzae</em>

Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins mediate intracellular vesicle fusion, which is an essential cellular process of the eukaryotic cells. To investigate the role of SNARE proteins in the rice blast fungus Magnaporthe oryzae, MoSec22, an ortholog of Saccharomyces cerevisiae SNARE protein Sec22, was identified and the MoSEC22 gene disrupted. MoSec22 restored a S. cerevisiae sec22 mutant in resistance to cell wall perturbing agents, and the ΔMosec22 mutant also exhibited defects in mycelial growth, conidial production, and infection of the host plant. Treatment with oxidative stress inducers indicated a breach in cell wall integrity, and staining and quantification assays suggested abnormal chitin deposition on the lateral walls of hyphae of the ΔMosec22 mutant. Furthermore, hypersensitivity to the oxidative stress correlates with the reduced expression of the extracellular enzymes peroxidases and laccases. Our study thus provides new evidence on the conserved function of Sec22 among fungal organisms and indicates that MoSec22 has a role in maintaining cell wall integrity affecting the growth, morphogenesis, and virulence of M. oryzae.可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体（SNARE）介导细胞内囊泡融合，这是真核细胞不可或缺的核心细胞过程。为探究SNARE蛋白在稻瘟病菌（Magnaporthe oryzae）中的功能，研究人员鉴定得到酿酒酵母（Saccharomyces cerevisiae）SNARE蛋白Sec22的直系同源蛋白MoSec22，并敲除了MoSEC22基因。MoSec22可回补酿酒酵母sec22突变体对细胞壁干扰剂的抗性缺陷；ΔMosec22敲除突变体则表现出菌丝生长、分生孢子产生以及寄主植物侵染能力的缺陷。通过氧化应激诱导剂处理实验发现，该突变体的细胞壁完整性遭到破坏；染色与定量检测实验显示，ΔMosec22突变体的菌丝侧壁几丁质沉积异常。此外，其对氧化应激的超敏性与胞外过氧化物酶和漆酶的表达下调密切相关。本研究为Sec22在真菌类群中的保守功能提供了新的实验证据，并表明MoSec22可通过维持细胞壁完整性，进而影响稻瘟病菌的生长、形态建成与致病力。