Piromyou Pongdet, Songwattana Pongpan, Wongdee Jenjira, Greetatorn Teerana, Boonchuen Pakpoom, Phimphong Tarnee, Nguyen Hien P, Manassila Monchai, Tanthanuch Waraporn, Maikhunthod Bussayarat, Teamtisong Kamonluck, Tittabutr Panlada, Boonkerd Nantakorn, Giraud Eric, Teaumroong Neung
Institute of Research and Development, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand.
School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand.
Sci Rep. 2025 Jun 5;15(1):19835. doi: 10.1038/s41598-025-05176-w.
Bradyrhizobium sp. DOA9 can nodulate a wide spectrum of legumes; however, unlike other bradyrhizobia, DOA9 carries a symbiotic plasmid harboring type III secretion system (T3SS) and several effector (T3E) genes, one of which encodes a putative type III effector SkP48. Here, we demonstrated the pivotal roles of SkP48 from Bradyrhizobium sp. DOA9 in inhibiting nodulation of various Vigna species and Crotalaria juncea and suppressing nodulation efficiency of Arachis hypogaea. By contrast, the nodulation efficiency of a SkP48 mutant did not differ significantly with the DOA9 wild-type strain on Macroptilium atropurpureum and Stylosanthes hamata. The SUMO domain of SkP48 is primarily responsible for the blocking nodulation phenotype V. radiata. An evolutionary analysis revealed that the SkP48 which contains a shikimate kinase and a SUMO protease (C48 cysteine peptidase) domain, SkP48 is distinct from other effectors previously reported in other bradyrhizobia and pathogenic bacteria. Our findings suggest that the putative T3E SkP48 is a key factor suppressing nodulation and nodule organogenesis in several legumes by activation of effector-triggered immunity through salicylic acid biosynthesis induction, which is deleterious to rhizobial infection. In addition, nodulation may be modulated by the function of defensins involved in jasmonic acid signalling in V. radiata SUT1.
慢生根瘤菌属DOA9菌株能够与多种豆科植物形成根瘤;然而,与其他慢生根瘤菌不同的是,DOA9携带一个共生质粒,该质粒含有III型分泌系统(T3SS)和多个效应蛋白(T3E)基因,其中一个基因编码一种假定的III型效应蛋白SkP48。在此,我们证明了慢生根瘤菌属DOA9菌株的SkP48在抑制多种豇豆属植物和猪屎豆的根瘤形成以及降低花生的根瘤形成效率方面发挥着关键作用。相比之下,SkP48突变体在大翼豆和柱花草上的根瘤形成效率与DOA9野生型菌株相比无显著差异。SkP48的SUMO结构域主要负责对绿豆根瘤形成的阻断表型。进化分析表明,含有莽草酸激酶和SUMO蛋白酶(C48半胱氨酸肽酶)结构域的SkP48与先前在其他慢生根瘤菌和病原菌中报道的其他效应蛋白不同。我们的研究结果表明,假定由水杨酸生物合成诱导激活效应子触发免疫从而抑制几种豆科植物根瘤形成和根瘤器官发生的T3E SkP48是一个关键因素,这对根瘤菌感染有害。此外,绿豆SUT1中参与茉莉酸信号传导的防御素功能可能会调节根瘤形成。