韦革宏、陈娟等《Plant Physiology》2024年

论文题目：Rhizobia cystathionine γ-lyase-derived H2S delays nodule senescence in soybean

论文作者：Wuyu Liu, Weiqin Zhang, Huaping Cheng, Yuxin Ding, Baihui Yao, Zhouping Shangguan, Gehong Wei*, Juan Chen *

论文摘要：

Hydrogen sulfide (H2S) is required for optimal establishment of soybean (Glycine max)-Sinorhizobium fredii symbiotic interaction, yet its role in regulating the nitrogen fixation-senescence transition remains poorly understood. A S. fredii cystathionine γ-lyase (CSE) mutant deficient in H2S synthesis showed early nodule senescence characterized by reduced nitrogenase activity, structural changes in nodule cells, and accelerated bacteroid death. In parallel, the CSE mutant facilitated the generation of reactive oxygen species (ROS) and elicited antioxidant responses. We observed that H2S-mediated persulfidation of cysteine C31/C80 in ascorbate peroxidase (APX) and C32 in APX2-modulated enzyme activity, thereby participating in hydrogen peroxide (H2O2) detoxification and delaying nodule senescence. Comparative transcriptomic analysis revealed a significant upregulation of GmMYB128, an MYB transcription factor (TF), in the CSE mutant nodules. Functional analysis through overexpression and RNAi lines of GmMYB128 demonstrated its role as a positive regulator in nodule senescence. MYB128-OE inoculated with the CSE mutant strain exhibited a reduction in nitrogenase activity and a significant increase in DD15 expression, both of which were mitigated by NaHS addition. Changes at the protein level encompassed the activation of plant defenses alongside turnover in carbohydrates and amino acids. Our results suggest that H2S plays an important role in maintaining efficient symbiosis and preventing premature senescence of soybean nodules.

H2S在大豆根瘤菌共生互作过程中发挥重要作用，然而其在大豆根瘤衰老调节过程中的作用机制仍需进一步探究。该研究发现，根瘤菌中编码H2S合成关键酶胱硫醚γ裂解酶的基因CSE突变导致其缺乏H2S合成能力，接种突变菌的大豆根瘤提前衰老，表现为固氮酶活性降低、豆血红蛋白含量降低、共生体膜分解和类菌体加速死亡等。同时，根瘤菌CSE突变促进大豆根瘤内活性氧（ROS）的产生并激活抗氧化响应。通过改良生物素转化法和质谱分析，鉴定到抗氧化酶APX的Cys31残基和Cys8残基以及APX2的Cys32残基会被H2S介导的硫巯基化修饰，H2S通过该蛋白翻译后修饰作用调节它们的抗氧化酶活性，从而参与调控大豆根瘤衰老。进一步通过比较转录组确定MYB家族转录因子在H2S调控大豆根瘤衰老过程中起到关键作用。GmMYB128在接种CSE突变菌的大豆根瘤中表达水平显著上调，毛根转化实验结果表明，GmMYB128过表达植株接种CSE突变根瘤菌后表现出叶绿素含量显著降低，固氮酶活性降低，根瘤衰老标志性基因DD15表达显著增加，分别过表达或干扰GmMYB128对根瘤功能没有显著影响，但在NaHS处理后，GmMYB128过表达/干扰植株的LbA和LbC1表达水平显著升高，固氮酶活性增强，明确了GmMYB128的表达受到H2S特异性调控，是大豆根瘤衰老的正调控因子。在本研究中，研究人员揭示了根瘤菌产生的H2S通过调节氧化还原稳态及转录因子调控大豆根瘤衰老的新机制，阐述了H2S在减缓大豆根瘤从固氮到衰老过程中的重要作用，对于开发基于H2S策略以延长大豆高效固氮时间和增加植物整体氮供应具有重要意义。

论文链接：https://doi.org/10.1093/plphys/kiae411