Wang Xun, Diao Zhijuan, Cao Chang, Liu Yan, Xia Na, Zhang Youlian, Lu Ling, Kong Fanyu, Zhou Houli, Chen Lizhe, Zhang Jing, Wang Bangsheng, Huang Ronghua, Tang Dingzhong, Li Shengping
State Key Laboratory of Ecological Control of Fujian-Taiwan Crop Pests, Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, Plant Immunity Center, College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
College of Agriculture, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
J Integr Plant Biol. 2024 Dec;66(12):2754-2771. doi: 10.1111/jipb.13783. Epub 2024 Oct 10.
Plants need to fine-tune defense responses to maintain a robust but flexible host barrier to various pathogens. Helix-loop-helix/basic helix-loop-helix (HLH/bHLH) complexes play important roles in fine-tuning plant development. However, the function of these genes in plant immunity and how they are regulated remain obscure. Here, we identified an atypical bHLH transcription factor, Oryza sativa (Os)HLH46, that interacts with rice receptor-like cytoplasmic kinase (RLCK) Os BRASSINOSTEROID-SIGNALING KINASE1-2 (OsBSK1-2), which plays a key role in rice blast resistance. OsBSK1-2 stabilized OsHLH46 both in vivo and in vitro. In addition, OsHLH46 positively regulates rice blast resistance, which depends on OsBSK1-2. OsHLH46 has no transcriptional activation activity and interacts with a typical bHLH protein, OsbHLH6, which negatively regulates rice blast resistance. OsbHLH6 binds to the promoter of OsWRKY45 and inhibits its expression, while OsHLH46 suppresses the function of OsbHLH6 by blocking its DNA binding and transcriptional inhibition of OsWRKY45. Consistent with these findings, OsWRKY45 was up-regulated in OsHLH46-overexpressing plants. In addition, the oshlh46 mutant overexpressing OsbHLH6 is more susceptible to Magnaporthe oryzae than is the wild type, suggesting that OsHLH46 suppresses OsbHLH6-mediated rice blast resistance. Our results not only demonstrated that OsBSK1-2 regulates rice blast resistance via the OsHLH46/OsbHLH6 complex, but also uncovered a new mechanism for plants to fine-tune plant immunity by regulating the HLH/bHLH complex via RLCKs.
植物需要微调防御反应，以维持对各种病原体强大而灵活的宿主屏障。螺旋-环-螺旋/碱性螺旋-环-螺旋（HLH/bHLH）复合体在微调植物发育过程中发挥重要作用。然而，这些基因在植物免疫中的功能以及它们是如何被调控的仍不清楚。在此，我们鉴定出一种非典型的bHLH转录因子，即水稻（Oryza sativa）OsHLH46，它与水稻类受体细胞质激酶（RLCK）Os油菜素类固醇信号激酶1-2（OsBSK1-2）相互作用，后者在水稻抗稻瘟病中起关键作用。OsBSK1-2在体内和体外均能稳定OsHLH46。此外，OsHLH46正向调控水稻抗稻瘟病，这依赖于OsBSK1-2。OsHLH46没有转录激活活性，它与一种典型的bHLH蛋白OsbHLH6相互作用，OsbHLH6负向调控水稻抗稻瘟病。OsbHLH6与OsWRKY45的启动子结合并抑制其表达，而OsHLH46通过阻断OsbHLH6与DNA的结合以及对OsWRKY45的转录抑制来抑制OsbHLH6的功能。与这些发现一致，OsWRKY45在过表达OsHLH46的植物中上调。此外，过表达OsbHLH6的oshlh46突变体比野生型更易受稻瘟病菌（Magnaporthe oryzae）侵染，这表明OsHLH46抑制OsbHLH6介导的水稻抗稻瘟病。我们的结果不仅证明了OsBSK1-2通过OsHLH46/OsbHLH6复合体调控水稻抗稻瘟病，还揭示了植物通过RLCKs调控HLH/bHLH复合体来微调植物免疫的新机制。
