Global Expression Profiling of Transcription Factor Genes Provides New Insights into Pathogenicity and Stress Responses in the Rice Blast Fungus

Because most efforts to understand the molecular mechanisms underpinning fungal pathogenicity have focused on studying the function and role of individual genes, relatively little is known about how transcriptional machineries globally regulate and coordinate the expression of a large group of genes involved in pathogenesis. Using quantitative real-time PCR, we analyzed the expression patterns of 206 transcription factor (TF) genes in the rice blast fungus Magnaporthe oryzae under 32 conditions, including multiple infection-related developmental stages and various abiotic stresses. The resulting data, which are publicly available via an online platform, provided new insights into how these TFs are regulated and potentially work together to control cellular responses to a diverse array of stimuli. High degrees of differential TF expression were observed under the conditions tested. More than 50% of the 206 TF genes were up-regulated during conidiation and/or in conidia. Mutations in ten conidiation-specific TF genes caused defects in conidiation. Expression patterns in planta were similar to those under oxidative stress conditions. Mutants of in planta inducible genes not only exhibited sensitive to oxidative stress but also failed to infect rice. These experimental validations clearly demonstrated the value of TF expression patterns in predicting the function of individual TF genes. The regulatory network of TF genes revealed by this study provides a solid foundation for elucidating how M. oryzae regulates its pathogenesis, development, and stress responses.目前，针对真菌致病分子机制的解析多聚焦于单个基因的功能与作用，学界对转录机器如何全局调控并协同表达大批致病相关基因的机制仍知之甚少。本研究采用实时荧光定量PCR（quantitative real-time PCR, qPCR）技术，对稻瘟病菌（Magnaporthe oryzae）的206个转录因子（transcription factor, TF）基因，在涵盖多个侵染相关发育阶段与多种非生物胁迫环境的32种条件下的表达模式进行了分析。本研究获得的数据集可通过在线平台公开获取，该数据为解析这些转录因子的调控模式及其潜在协同调控细胞响应多种刺激的机制提供了新视角。在所测试的条件下，转录因子基因呈现出显著的差异表达特征：206个转录因子基因中有超过50%在产孢过程中或分生孢子内呈现上调表达。对10个产孢特异性转录因子基因进行突变后，菌株均出现了产孢缺陷表型。病菌在宿主植物体内的表达模式与氧化胁迫环境下的表达模式高度相似。对植物体内诱导表达的基因进行突变后，突变株不仅对氧化胁迫更为敏感，同时丧失了侵染水稻的能力。上述实验验证清晰证实了转录因子表达模式可用于预测单个转录因子基因功能的价值。本研究揭示的转录因子基因调控网络，为解析稻瘟病菌如何调控其致病过程、发育进程与胁迫响应机制提供了坚实的研究基础。