禾谷镰孢半胱天冬氨酸酶FgCas4的生物学功能

Biological function of the caspase FgCas4 in Fusarium

半胱天冬氨酸酶(caspase)在哺乳动物中参与调控细胞凋亡过程,控制着多种疾病的发生发展。本研究利用基因敲除和回补的方法,获得了禾谷镰孢中半胱天冬氨酸酶基因FgCas4的敲除突变体ΔFgCas4和回补体ΔFgCas4-C。通过观察分析发现,基因FgCas4的缺失并不影响禾谷镰孢(Fusarium graminearum)的生长速率、菌落形态、分生孢子产量、致病和产毒。但是,敲除突变体ΔFgCas4的菌丝分支变多且具有3个隔膜的分生孢子比例较野生型和回补体增加了8.7%。对外界环境胁迫因子耐受性测定显示,ΔFgCas4对杀菌剂和金属离子的敏感性显著增加,同时其细胞内脂滴含量增多,对渗透胁迫因子抗性变强。亚细胞定位发现,半胱天冬氨酸酶FgCas4定位于液泡中。此外,基因FgCas4的缺失导致F.graminearum细胞自噬过程明显提前。上述研究结果表明,F.graminearum中半胱天冬氨酸酶FgCas4主要在菌体无性繁殖、对不同环境胁迫的应答以及细胞自噬过程中发挥重要作用。

Caspase is known to be involved in modulating apoptosis in mammals,controlling the occurrence and development of various diseases.In present study,the null mutantΔFgCas4 and complemented strainΔFgCas4-C of the caspase gene FgCas4 were obtained by gene disruption and complementation respectively in Fusarium graminearum.We observed that the FgCas4 deletion mutant(ΔFgCas4)did not affect the growth rate,colony morphology,conidiation,virulence and DON production.However,the deletion mutantΔFgCas4 exhibited more hyphal branching and percentage of conidia with 3 septa increased by 8.7%compared to wild type PH-1 and complemented strainΔFgCas4-C.External environmental stress assays showed that the gene disrupt mutantΔFgCas4 became more sensitive to tested fungicides and metal ions.In addition,the lack of FgCas4 led to dramatically increased lipid droplet biosynthesis as well as increased resistance to osmotic stress agents.Subcellular localization showed that the caspase FgCas4 localized in vacuoles.On the other,the loss of FgCas4 resulted in earlier process of autophagy.Taken together,our study provides evidences that the caspase FgCas4 of Fusarium graminearum plays important roles in asexual reproduction,various environmental stress responses and auto-phagy regulation.