Bradyrhizobium sp. strain SUTN9-2 is a symbiotic and endophytic diazotrophic bacterium found in legume and rice plants and has the potential to promote growth. The present results revealed that SUTN9-2 underwent cell enlargement, increased its DNA content, and efficiently performed nitrogen fixation in response to rice extract. Some factors in rice extract induced the expression of cell cycle and nitrogen fixation genes. According to differentially expressed genes (DEGs) from the transcriptomic analysis, SUTN9-2 was affected by rice extract and the deletion of the bclA gene. The up-regulated DEGs encoding a class of oxidoreductases, which act with oxygen atoms and may have a role in controlling oxygen at an appropriate level for nitrogenase activity, followed by GroESL chaperonins are required for the function of nitrogenase. These results indicate that following its exposure to rice extract, nitrogen fixation by SUTN9-2 is induced by the collective effects of GroESL and oxidoreductases. The expression of the sensitivity to antimicrobial peptides transporter (sapDF) was also up-regulated, resulting in cell differentiation, even when bclA (sapDF) was mutated. This result implies similarities in the production of defensin-like antimicrobial peptides (DEFs) by rice and nodule-specific cysteine-rich (NCR) peptides in legume plants, which affect bacterial cell differentiation.

中文翻译：

---

水稻内生慢生根瘤菌细胞分化机制及其固氮作用

慢生根瘤菌 sp. SUTN9-2 菌株是一种存在于豆科植物和水稻植物中的共生内生固氮细菌，具有促进生长的潜力。目前的结果表明，SUTN9-2 经历了细胞增大，增加了其 DNA 含量，并响应大米提取物有效地进行固氮。大米提取物中的一些因子诱导细胞周期和固氮基因的表达。根据转录组分析的差异表达基因（DEG），SUTN9-2受到大米提取物和bclA基因缺失的影响。上调的 DEG 编码一类氧化还原酶，与氧原子作用，可能在将氧控制在适当水平以促进固氮酶活性方面发挥作用，其次是固氮酶功能所需的 GroESL 伴侣蛋白。这些结果表明，在暴露于大米提取物后，SUTN9-2 的固氮作用是由 GroESL 和氧化还原酶的共同作用诱导的。即使 bclA (sapDF) 发生突变，抗菌肽转运蛋白 (sapDF) 敏感性的表达也上调，导致细胞分化。这一结果表明，水稻产生的类防御素抗菌肽（DEF）与豆科植物中的根瘤特异性富含半胱氨酸（NCR）肽具有相似性，会影响细菌细胞的分化。