National Key Laboratory of Crop Genetic Improvement, Center of Integrative Biology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng 475001, China.
National Key Laboratory of Crop Genetic Improvement, Center of Integrative Biology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Mol Plant. 2021 Mar 1;14(3):488-502. doi: 10.1016/j.molp.2020.12.015. Epub 2020 Dec 21.
Legumes establish symbiotic associations with rhizobia for biological nitrogen fixation. This process is highly regulated by various abiotic stresses, but the underlying genetic and molecular mechanisms remain largely unknown. In this study, we discovered that the glycogen synthase kinase 3 (GSK3)-like kinase, GmSK2-8, plays an important role in inhibiting symbiotic signaling and nodule formation in soybean (Glycine max) under salt stress. We found that GmSK2-8 is strongly induced in soybean under high-salt conditions, while GmSK2-8 could interact with two G. max Nodulation Signaling Pathway 1 (GmNSP1) proteins, GmNSP1a and GmNSP1b; these key transcription factors are essential for rhizobial infection, nodule initiation, and symbiotic gene expression in soybean. Furthermore, we demonstrated that GmSK2-8 phosphorylates the LHRI domain of GmNSP1a, inhibits its binding to the promoters of symbiotic genes, and thus suppresses nodule formation under salt stress. Knockdown of GmSK2-8 and its close homologs also resulted in reduced plant sensitivity to salt stress during nodule formation. Taken together, our findings indicate that GSK3-like kinases directly regulate the activities of GmNSP1s to mediate salt-inhibited legume-rhizobium symbiosis, providing novel targets for improving symbiotic nitrogen fixation under environmental stress conditions in soybean and possibly other legumes.
豆科植物与根瘤菌建立共生关系以进行生物固氮。这个过程受到各种非生物胁迫的高度调节，但潜在的遗传和分子机制在很大程度上仍然未知。在这项研究中，我们发现糖原合酶激酶 3 (GSK3)-样激酶 GmSK2-8 在盐胁迫下大豆中抑制共生信号和根瘤形成中起重要作用。我们发现 GmSK2-8 在大豆受到高盐条件强烈诱导，而 GmSK2-8 可以与两种大豆结瘤信号通路 1 (GmNSP1) 蛋白 GmNSP1a 和 GmNSP1b 相互作用；这些关键转录因子对于根瘤菌感染、根瘤起始和大豆中的共生基因表达是必需的。此外，我们证明 GmSK2-8 磷酸化 GmNSP1a 的 LHRI 结构域，抑制其与共生基因启动子的结合，从而抑制盐胁迫下的根瘤形成。GmSK2-8 及其密切同源物的敲低也导致植物在根瘤形成过程中对盐胁迫的敏感性降低。总之，我们的研究结果表明 GSK3 样激酶直接调节 GmNSP1 的活性，以介导盐抑制豆科植物-根瘤菌共生，为在大豆和可能其他豆科植物中改善环境胁迫条件下的共生固氮提供了新的靶标。
