Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Ministry of Education, Nanjing, China.
PLoS One. 2012;7(6):e40246. doi: 10.1371/journal.pone.0040246. Epub 2012 Jun 29.
PsSAK1, a mitogen-activated protein (MAP) kinase from Phytophthora sojae, plays an important role in host infection and zoospore viability. However, the downstream mechanism of PsSAK1 remains unclear. In this study, the 3'-tag digital gene expression (DGE) profiling method was applied to sequence the global transcriptional sequence of PsSAK1-silenced mutants during the cysts stage and 1.5 h after inoculation onto susceptible soybean leaf tissues. Compared with the gene expression levels of the recipient P. sojae strain, several candidates of Myb family were differentially expressed (up or down) in response to the loss of PsSAK1, including of a R2R3-type Myb transcription factor, PsMYB1. qRT-PCR indicated that the transcriptional level of PsMYB1 decreased due to PsSAK1 silencing. The transcriptional level of PsMYB1 increased during sporulating hyphae, in germinated cysts, and early infection. Silencing of PsMYB1 results in three phenotypes: a) no cleavage of the cytoplasm into uninucleate zoospores or release of normal zoospores, b) direct germination of sporangia, and c) afunction in zoospore-mediated plant infection. Our data indicate that the PsMYB1 transcription factor functions downstream of MAP kinase PsSAK1 and is required for zoospore development of P. sojae.
大豆疫霉丝氨酸/苏氨酸蛋白激酶 1（PsSAK1）在植物病原侵染过程中发挥重要作用。然而，PsSAK1 的下游机制仍不清楚。本研究应用 3'-tag 数字基因表达（DGE）谱分析方法，对大豆疫霉无功能突变体在休止孢阶段和接种敏感大豆叶片后 1.5 h 的基因表达谱进行了测序。与受体 P. sojae 菌株的基因表达水平相比，PsSAK1 缺失后，多个 Myb 家族候选基因（上调或下调）发生差异表达，包括 R2R3 型 Myb 转录因子 PsMYB1。qRT-PCR 结果表明，PsSAK1 沉默导致 PsMYB1 的转录水平降低。PsMYB1 的转录水平在孢子丝、萌发的休止孢和早期侵染过程中增加。PsMYB1 沉默导致三种表型：a）细胞质不能分裂成单核游动孢子或释放正常游动孢子，b）游动孢子囊直接萌发，c）游动孢子介导的植物侵染功能丧失。研究结果表明，PsMYB1 转录因子位于 MAP 激酶 PsSAK1 的下游，是大豆疫霉游动孢子发育所必需的。
