烟曲霉蛋白激酶A催化亚基对孢子萌发和抗氧化损伤的调节作用

Catalytic subunit of PKA in aspergillus fumigatus regulates its germination and resistance to oxidative damage

目的烟曲霉（Aspergillus fumigatus）是一种重要的条件致病性真菌,在免疫受损宿主体内引起侵袭性曲霉病。cAMP-PKA信号通路调控真菌的生长、发育等重要过程。文中检测了烟曲霉野生株（WT株）及蛋白激酶A（protein kinase a,PKA）催化亚基基因突变株（ΔpkaC1株）的孢子萌发曲线、菌株生长、对H2O2的敏感性,分析pkaC1在烟曲霉孢子萌发、抗氧化损伤中的作用。方法WT株和ΔpkaC1株孢子接种于曲霉菌基础培养液（Aspergillusminimal medium,AMM）,观察孢子萌发曲线和菌株径向生长曲线。孢子与不同浓度H2O2作用后涂于AMM上培养,计数残存菌落个数。结果WT株和ΔpkaC1株孢子均于培养4.5 h后开始出现第1个萌发管,ΔpkaC1株孢子萌发1个或1个以上萌发管的萌发动力学降低;ΔpkaC1出现第2个萌发管的时间相对于WT株推迟约1 h,于培养13 h时,WT株100%萌发2个或2个以上萌发管,此时ΔpkaC1株萌发2个或2个以上萌发管的萌发率约为42%。ΔpkaC1株生长缓慢,同时期菌落直径仅为WT株的1/3~1/2。低浓度的H2O2（0.005%~0.050%）处理后,WT株与ΔpkaC1株孢子的存活率差异有显著统计学意义（P〈0.01）;对高浓度H2O2（0.100%~0.500%）,存活率差异无统计学意义（P〉0.05）。结论cAMP-PKA信号通路中PKA催化亚基在烟曲霉孢子萌发和抗氧化损伤中起着调节作用。

Objective Aspergillus fumigatus is a major opportunistic pathogenic fungus in immunocompromised hosts,causing invasive aspergillosis.The cAMP-PKA signaling pathway plays an important role in regulating the growth and development of many fungi.This study was to investigate the role of the catalytic subunit of PKA（pkaC1） in the germination and oxidative damage resistance of aspergillus fumigatus by detecting its germination rate,radial growth and sensitivity to hydrogen peroxide（H2O2） of a mutant with a defect in ΔpkaC1 with its parent A.fumigatus wild type（WT）.Methods The conidia of WT and ΔpkaC1 were incubated in AMM,and their germination and growth rates were measured.Then they were mixed with different concentrations of H2O2,and the numbers of surviving conidia were counted.Results Both WT and ΔpkaC1 conidia started to germinate after incubated for 4.5 hours,but kinetically the germination of ΔpkaC1 was slower and that of the second ΔpkaC1 germ tube was delayed for an hour.At 13 hours,2 or more germ tubes were germinated in 100% of WT in comparison with 42% in ΔpkaC1.ΔpkaC1 grew slowly,its radial growth only 1/3~1/2 that of WT.The survival rates of WT and ΔpkaC1 were significantly different after treated with H2O2 at low concentrations of 0.005%~0.050%（P0.01）,but not at high concentrations of 0.100%~0.500%（P0.05）.Conclusion The catalytic subunit of PKA in the cAMP-PKA signaling pathway of A.fumigatus plays an important role in regulating its germination and resistance to oxidative damage.