Homologous recombination (HR) and nonhomologous end joining (NHEJ) are considered the two main double-strand break (DSB) repair approaches in eukaryotes. Inhibiting the activities of the key component in NHEJ commonly enhances the efficiency of targeted gene knockouts or affects growth and development in higher eukaryotes. However, little is known about the roles of the NHEJ pathway in foliar pathogens. Here we identified a gene designated StKU80, which encodes a putative DNA end-binding protein homologous to yeast Ku80, in the foliar pathogen Exserohilum turcicum. Conserved domain analysis showed that the typical domains VWA, Ku78 and Ku-PK-bind are usually present in Ku70/80 proteins in eukaryotes and are also present in StKu80. Phylogenetic analysis indicated that StKu80 is most closely related to Ku80 (XP_001802136.1) from Parastagonospora nodorum, followed by Ku80 (AGF90044.1) from Monascus ruber. Furthermore, the gene knockout mutants ΔStKU80-1 and ΔStKU80-2 were obtained. These mutants displayed longer septas, thinner cell walls, smaller amounts of substances on cell wall surfaces, and more mitochondria per cell than the wild-type (WT) strain but similar HT-toxin activity. The mutants did not produce conidia and mature appressoria. On the other hand, the mutants were highly sensitive to H2O2, but not to ultraviolet radiation. In summary, the StKU80 plays devious roles in regulating the development of E. turcicum.

同源重组（HR）和非同源末端连接（NHEJ）被认为是真核生物的两种主要的双链断裂（DSB）修复方法。抑制NHEJ中关键成分的活性通常会提高靶向基因敲除的效率或影响高级真核生物的生长和发育。然而，关于叶面病原体中NHEJ途径的作用了解甚少。在这里，我们确定了一个名为StKU80的基因，该基因编码在叶病原体Exserohilum turcicum中与酵母Ku80同源的推定的DNA末端结合蛋白。保守域分析表明，典型的域VWA，Ku78和Ku-PK-bind通常存在于真核生物的Ku70 / 80蛋白中，也存在于StKu80中。系统发育分析表明，StKu80与来自Nostratum Nodorum的Ku80（XP_001802136.1）密切相关，其次是来自红曲霉的Ku80（AGF90044.1）。此外，基因敲除突变体ΔStKU80-1和ΔStKU80-2获得了。与野生型（WT）菌株相比，这些突变体显示出更长的间隔，更薄的细胞壁，更小的细胞壁表面物质以及每个细胞更多的线粒体，但具有类似的HT毒素活性。突变体不产生分生孢子和成熟的附子。另一方面，这些突变体对H2O2高度敏感，但对紫外线辐射不敏感。综上所述，StKU80起着调节的发展迂回角色玉米大斑病菌。