State Key Laboratory of Rice Biology & Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou, China.
The Sainsbury Laboratory, Norwich Research Park, Norwich, UK.
Cell Microbiol. 2021 Oct;23(10):e13370. doi: 10.1111/cmi.13370. Epub 2021 Jul 16.
In the rice blast fungus Magnaporthe oryzae, the cAMP signalling pathway plays a critical role in regulating leaf surface recognition and the initiation of appressorium development. Direct downstream targets of the cAMP signalling pathway are, however, not well-characterised. The MoSom1 protein functions downstream of the cAMP dependent protein kinase A (cAMP-PKA) and is essential for infection-related morphogenesis and pathogenicity. In this study, we show that mutation of a putative PKA phosphorylation site in MoSom1 is essential for its role in appressorium differentiation and pathogenicity in M. oryzae. Mutation of serine 227 in MoSom1 by deletion or serine (S) substitution to alanine (A), valine (V) or tyrosine (Y), resulted in defects of conidiation, appressorium-like structure formation and fungal pathogenicity. Western blot analysis confirmed that S227 in MoSom1 is a putative PKA phosphorylation site. Furthermore, a ΔMosom1 mutant showed reduced expression of PMK1 and was defective in Pmk1 phosphorylation, indicating that the Pmk1 mitogen-activated protein kinase (MAPK) acts downstream of MoSom1 in M. oryzae. We conclude that the cAMP-PKA pathway may regulate the Pmk1 MAPK pathway through MoSom1 during rice infection by the blast fungus. TAKE AWAYS: S227 is crucial for MoSom1 function in M. oryzae. S227 in MoSom1 was identified as a putative PKA phosphorylation site in M. oryzae. S227 is essential for infection-related morphogenesis and pathogenicity in M. oryzae.
在稻瘟病菌 Magnaporthe oryzae 中，cAMP 信号通路在调控叶片表面识别和启动附着胞发育中起着关键作用。然而，cAMP 信号通路的直接下游靶标尚未得到很好的描述。MoSom1 蛋白是 cAMP 依赖性蛋白激酶 A（cAMP-PKA）的下游产物，对于感染相关的形态发生和致病性是必不可少的。在本研究中，我们表明 MoSom1 中假定的 PKA 磷酸化位点的突变对于其在附着胞分化和稻瘟病菌致病性中的作用是必不可少的。MoSom1 中丝氨酸 227 的突变通过缺失或丝氨酸（S）取代为丙氨酸（A）、缬氨酸（V）或酪氨酸（Y），导致分生孢子形成、类似附着胞结构形成和真菌致病性缺陷。Western blot 分析证实 MoSom1 中的 S227 是一个假定的 PKA 磷酸化位点。此外，ΔMosom1 突变体显示 PMK1 的表达减少，并且 Pmk1 磷酸化缺陷，表明 PMK1 丝裂原活化蛋白激酶（MAPK）在稻瘟病菌中作为 MoSom1 的下游发挥作用。我们得出结论，cAMP-PKA 途径可能通过稻瘟病菌感染过程中的 MoSom1 来调节 Pmk1 MAPK 途径。结论：S227 对 MoSom1 在稻瘟病菌中的功能至关重要。S227 在 MoSom1 中被鉴定为稻瘟病菌中假定的 PKA 磷酸化位点。S227 对稻瘟病菌中与感染相关的形态发生和致病性是必不可少的。
