Guangxi Key Laboratory for Agro-Environment and Agro, Product Safety, National Demonstration Center for Experimental Plant Science Education, College of Agriculture, Guangxi University, Nanning, Guangxi 530004, China.
Guangxi Key Laboratory for Agro-Environment and Agro, Product Safety, National Demonstration Center for Experimental Plant Science Education, College of Agriculture, Guangxi University, Nanning, Guangxi 530004, China.
Ecotoxicol Environ Saf. 2022 Dec 1;247:114248. doi: 10.1016/j.ecoenv.2022.114248. Epub 2022 Nov 1.
Halosulfuron-methyl (HSM) is a new and highly effective sulfonylurea herbicide widely used in weed control, but its residue in the environment poses a potential risk to soybean. Soybean-rhizobium symbiotic nitrogen fixation is crucial for sustainable agricultural development and ecological environment health. However, the impact of HSM on the symbiosis between soybean and rhizobium is unclear. In this study, the effects of HSM on the soybean-rhizobium symbiotic process and nitrogen fixation were investigated by means of transcriptomic and physiological analyses. Treatment with a concentration of HSM less than 0.5 mg L had no effect on rhizobium growth, but significantly reduced nodules number, the biomass of soybean nodules, and nitrogenase activity in root nodules (P < 0.05). Transcriptomic analysis showed that differentially expressed genes (DEGs) involved in NH assimilation were significantly downregulated (P < 0.05). In addition, the activities of NH assimilation enzymes were markedly reduced. This result was further confirmed by the accumulation of NH in root nodules, indicating that the inhibition of nitrogen fixation by HSM may be caused by excessive NH accumulation in root nodules. Furthermore, DEGs involved in flavonoid synthesis, phytohormone biosynthesis, and phytohormone signaling transduction were significantly downregulated (P < 0.05), which was consistent with the decrease in flavonoid and phytohormone contents determined in this study. These results suggested that HSM may inhibit soybean nodulation by inhibiting flavonoid synthesis in soybean roots, disrupting the balance of plant endogenous hormones in roots during symbiosis, and blocking the transmission of hormone signals during the symbiosis. Our findings provide new insights into the effects of HSM on the legume-rhizobium nodule symbiotic process.
甲磺隆（HSM）是一种新型、高效的磺酰脲类除草剂，广泛用于杂草防治，但它在环境中的残留对大豆构成潜在风险。大豆-根瘤菌共生固氮对可持续农业发展和生态环境健康至关重要。然而，HSM 对大豆-根瘤菌共生关系的影响尚不清楚。本研究采用转录组学和生理分析方法，研究了 HSM 对大豆-根瘤菌共生过程和固氮的影响。浓度低于 0.5mg/L 的 HSM 处理对根瘤菌生长没有影响，但显著减少了根瘤数量、大豆根瘤的生物量和根瘤中的固氮酶活性（P<0.05）。转录组分析表明，参与 NH 同化的差异表达基因（DEGs）显著下调（P<0.05）。此外，NH 同化酶的活性明显降低。这一结果进一步通过根瘤中 NH 的积累得到证实，表明 HSM 对固氮的抑制可能是由于根瘤中 NH 积累过多所致。此外，参与类黄酮合成、植物激素生物合成和植物激素信号转导的 DEGs 显著下调（P<0.05），这与本研究中测定的类黄酮和植物激素含量的减少相一致。这些结果表明，HSM 可能通过抑制大豆根系中类黄酮的合成、破坏共生过程中根系中植物内源激素的平衡以及阻断激素信号在共生过程中的传递来抑制大豆结瘤。本研究结果为 HSM 对豆科植物-根瘤菌共生过程的影响提供了新的见解。
