TOR途径对玉米大斑病菌发育调控作用的研究

Regulatory effect of TOR signal pathway on the development of Setosphaeria turcica

大斑刚毛球腔菌(Setosphaeria turcica)引起的玉米大斑病(Northern corn leaf blight)是危害玉米的一种重要真菌性叶部病害。大量研究表明,真菌病原物的生长发育及致病性受多种信号转导途径的调控,其中TOR是雷帕霉素的作用靶标,它既是一种蛋白激酶,也是一种信号转导分子,在调控细胞生长方面起核心作用。本试验用雷帕霉素处理玉米大斑病菌菌株,观察其菌落生长、菌丝形态、产孢量、附着胞形成及穿透情况。结果表明,当雷帕霉素处理浓度为25 ng·mL-1时,菌落直径为1.65 cm,抑菌率达到81.9%,雷帕霉素对菌丝体生长的半抑制浓度IC50为0.665 ng·mL-1;病菌产孢量为0.1×104个·mL-1,仅为对照组的10%。随着雷帕霉素浓度的增加,分生孢子萌发、附着胞形成及穿透能力均被不同程度抑制,但形态未出现异常。qRT-PCR分析表明,雷帕霉素处理后,StTOR、StTAP42及PP2A结构亚基StPP2A-A和调节亚基StPP2A-B的表达均显著下调。第5 d时,分别降低至甲醇对照组的约42%、38%、47%和42%;第10 d时,分别降低至甲醇对照组的约36%、31%、26%和21%,而PP2A的催化亚基StPP2A-C表达量变化不显著,表明雷帕霉素在抑制TOR活性的同时,还可以抑制StTOR、StTAP42及PP2A结构亚基和调节亚基的转录。本研究为深入探究TOR信号通路对玉米大斑病菌发育过程的调控作用提供了依据。

Setosphaeria turcica,an important fungal pathogen,gives rise to a serious threat to corn production.TOR as the target of rapamycin is a kind of protein kinase family and plays a central role in regulation of cell growth.In this study,effects of rapamycin on growth,mycelial morphology,sporulation,appressoria formation and penetration of S.turcica were investigated.When treated with 25 ng·mL-1 rapamycin,the colony diameter was 1.65 cm,the inhibitory rate reached 81.9%,the IC50 of mycelium growth was 0.665 ng·mL-1,and the sporulation of the pathogen was 0.1×104 spores per milliliter,which were 10%of that of the control.With increase of rapamycin concentration,the germination of conidia,the development and penetration of appressoria were inhibited by different degrees,but their morphology was normal.qRT-PCR analysis showed that after rapamycin treatment,the expression level of St TOR,St TAP42,St PP2A-A,St PP2A-B were decreased significantly.On the 5 th day,they were reduced to about 42%,38%,47%and 42%of the control,respectively.On the 10 th day,they were reduced to about 36%,31%,26%and 21%of the control,respectively.However,the expression level of St PP2A-C didn’t change significantly.These results indicate that rapamycin inhibits TOR activity and causes transcription inhibition of St TOR,St TAP42,and the structural subunit and regulatory subunit of PP2A.This study provides a basis for further exploring regulatory role of the TOR signaling pathway in the development process of S.turcica.