禾谷镰孢菌中β-1,4-D-内切木聚糖酶基因FgXYLD的生物学功能

Biological function of the endo-1,4-β-xylanase D gene FgXYLD in Fusarium graminearum

由禾谷镰孢菌Fusarium graminearum为主要病原菌引起的小麦赤霉病是小麦三大病害之一,对小麦的产量和质量均构成巨大威胁。β-1,4-D-内切木聚糖酶作为一种重要的水解酶,能够降解植物细胞壁的主要成分之一半纤维素,进而在病菌侵染寄主植物时发挥作用。为进一步揭示禾谷镰孢菌中β-1,4-D-内切木聚糖酶基因FgXYLD的功能,本实验将该基因在禾谷镰孢菌中敲除,通过研究FgXYLD基因敲除突变体的基本特性以明晰该基因功能。结果发现,FgXYLD基因的缺失并不影响禾谷镰孢菌的菌落形态、菌落生长速率与分生孢子萌发,但影响分生孢子的产生;在外界胁迫实验中,敲除突变体对戊唑醇、Na^(+)、K^(+)耐受性增强;在有性生殖实验中,敲除突变体的子囊壳形成延迟,子囊孢子喷发有明显缺陷;在致病力实验中,敲除突变体的致病力低于野生型;在DON毒素测定实验中,敲除突变体DON毒素产生量明显减少,部分产毒基因表达水平有所降低。以上结果表明,β-1,4-D-内切木聚糖酶基因FgXYLD在禾谷镰孢菌的逆境胁迫、有性生殖与致病力中扮演一定功能。

Fusarium head blight,caused by Fusarium graminearum as the main pathogen,is one of the three major diseases of wheat,posing a great threat to both the yield and quality of wheat.Endo-1,4-β-D-xylanase,as an important hydrolase,is capable of degrading the major component of the plant cell wall,hemicellulose,and plays a role in the infection of host plants.In order to further reveal the function of the endo-1,4-β-D-xylanase gene FgXYLD,the gene was knocked out in F.graminearum,and the basic characteristics of the FgXYLD knockout mutant were investigated.It was found that deletion of FgXYLD gene did not affect colony morphology,colony growth rate and conidial germination,but affected conidial production.The knockout mutant was more tolerant to tebuconazole,Na+,and K+in the stress tolerance experiment.Sexual reproduction experiment showed that the formation of perithecium was delayed and the release of ascospores was obviously influenced.The pathogenicity of the knockout mutant was weaker than that of the wild-type.The production of DON toxin in knockout mutant was significantly reduced,and the expression level of some toxin-producing genes was decreased.These results indicate that the endo-1,4-β-D-xylanase gene FgXYLD plays a role in stress tolerance,sexual reproduction and pathogenicity of F.graminearum.