Chen Yuedan, Yin Shuai, Yang Yinong, Xie Kabin
National Key Laboratory of Crop Genetic Improvement, Hubei Hongshan Laboratory, Huazhong Agricultural University, Wuhan, 430070, China.
Hubei Key Laboratory of Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China.
Plant J. 2025 Jun;122(6):e70285. doi: 10.1111/tpj.70285.
Plant mitogen-activated protein kinases (MAPKs) are pivotal regulators of the innate immune signaling pathway and phosphorylate an array of transcription factors to reprogram the expression of disease-responsive genes. However, how MAPKs reprogram plant gene expression at the posttranscriptional level is poorly understood. Here, we show that double-stranded RNA-binding protein 1.4 (OsDRB1.4) is a substrate of OsMPK5 in rice. OsDRB1.4 belongs to a monocot-specific subgroup of the DRB family and contains a noncanonical MAPK interaction motif in its C terminus. OsMPK5 mainly phosphorylates the 216th serine of OsDRB1.4 in vivo. Silencing and knockout of OsDRB1.4 increased rice defense against Magnaporthe oryzae and increased the expression of 34 genes, including PR5 and three R-GENE ANALOG genes, whereas OsDRB1.4-overexpressing rice was more susceptible to blast disease. In contrast, overexpressing OsDRB1.4 with the phosphorylation sites mutated in rice did not affect disease susceptibility, suggesting that these phosphorylation sites are critical for OsDRB1.4 functionality. A total of 130 transcript units and 171 annotated repetitive sequence transcripts were identified as the RNA partners of OsDRB1.4 through targeted RNA editing. RNA electrophoretic mobility shift assays validated that OsDRB1.4 directly bound the stem-loop dsRNAs of microRNA precursors and the 3'-UTRs of protein-coding mRNAs. Further analysis indicated that OsDRB1.4 positively regulated the expression of mature osa-miR7695 and osa-miR2871. More importantly, OsDRB1.4 bound stem-loop dsRNA in the 3'-UTR of Pi-ta RESISTANCE (Ptr) and negatively affected protein expression. Together, our data reveal that the OsMPK5-OsDRB1.4 module negatively regulates rice defense against M. oryzae through the posttranscriptional suppression of defense-related genes.
植物丝裂原活化蛋白激酶（MAPKs）是先天免疫信号通路的关键调节因子，可磷酸化一系列转录因子，从而重新编程疾病响应基因的表达。然而，人们对MAPKs如何在转录后水平上重新编程植物基因表达了解甚少。在这里，我们表明双链RNA结合蛋白1.4（OsDRB1.4）是水稻中OsMPK5的底物。OsDRB1.4属于DRB家族的单子叶植物特异性亚组，在其C末端含有一个非典型的MAPK相互作用基序。OsMPK5在体内主要磷酸化OsDRB1.4的第216位丝氨酸。沉默和敲除OsDRB1.4增强了水稻对稻瘟病菌的防御能力，并增加了34个基因的表达，包括PR5和三个R基因类似物基因，而过量表达OsDRB1.4的水稻对稻瘟病更敏感。相反，在水稻中过量表达具有突变磷酸化位点的OsDRB1.4并不影响疾病易感性，这表明这些磷酸化位点对OsDRB1.4的功能至关重要。通过靶向RNA编辑，共鉴定出130个转录单元和171个注释的重复序列转录本作为OsDRB1.4的RNA伴侣。RNA电泳迁移率变动分析验证了OsDRB1.4直接结合微小RNA前体的茎环双链RNA和蛋白质编码mRNA的3'-UTR。进一步分析表明，OsDRB1.4正向调节成熟osa-miR7695和osa-miR2871的表达。更重要的是，OsDRB1.4结合Pi-ta抗性（Ptr）的3'-UTR中的茎环双链RNA，并对蛋白质表达产生负面影响。总之，我们的数据表明，OsMPK5-OsDRB1.4模块通过对防御相关基因的转录后抑制，负向调节水稻对稻瘟病菌的防御。
