Coordinated regulation of symbiotic adaptation by NodD proteins and NolA in the type I peanut bradyrhizobial strain Bradyrhizobium zhanjiangense CCBAU51778

• Published in: Microbiological research 2022-12, Vol.265, p.127188-127188, Article 127188
• Main Authors: Shang, Jiao Ying, Zhang, Pan, Jia, Yu Wen, Lu, Yi Ning, Wu, Yue, Ji, Shuang, Chen, La, Wang, En Tao, Chen, Wen Xin, Sui, Xin Hua
• Format: Article
• Language: English
• Subjects: Bradyrhizobium; Coordinated regulation; exopolysaccharides; mung beans; NodD; nodulation; NolA; operon; Peanut bradyrhizobia; peanuts; symbiosis; Symbiotic adaptation; type III secretion system
• ISSN: 0944-5013; 1618-0623
• DOI: 10.1016/j.micres.2022.127188

Type I peanut bradyrhizobial strains can establish efficient symbiosis in contrast to symbiotic incompatibility induced by type II strains with mung bean. The notable distinction in the two kinds of key symbiosis-related regulators nolA and nodD close to the nodABCSUIJ operon region between these two types of peanut bradyrhizobia was found. Therefore, we determined whether NolA and NodD proteins regulate the symbiotic adaptations of type I strains to different hosts. We found that NodD1-NolA synergistically regulated the symbiosis between the type I strain Bradyrhizobium zhanjiangense CCBAU51778 and mung bean, and NodD1–NodD2 jointly regulated nodulation ability. In contrast, NodD1-NolA coordinately regulated nodulation ability in the CCBAU51778-peanut symbiosis. Meanwhile, NodD1 and NolA collectively contributes to competitive nodule colonization of CCBAU51778 on both hosts. The Fucosylated Nod factors and intact type 3 secretion system (T3SS), rather than extra nodD2 and full-length nolA, were critical for effective symbiosis with mung bean. Unexpectedly, T3SS-related genes were activated by NodD2 but not NodD1. Compared to NodD1 and NodD2, NolA predominantly inhibits exopolysaccharide production by promoting exoR expression. Importantly, this is the first report that NolA regulates rhizobial T3SS-related genes. The coordinated regulation and integration of different gene networks to fine-tune the expression of symbiosis-related genes and other accessory genes by NodD1-NolA might be required for CCBAU51778 to efficiently nodulate peanut. This study shed new light on our understanding of the regulatory roles of NolA and NodD proteins in symbiotic adaptation, highlighting the sophisticated gene networks dominated by NodD1-NolA. •NodD1-NolA synergistically regulated CCBAU51778 symbioses with mung bean and peanut.•NodD2 but not NodD1 could activate type 3 secretion system (T3SS)-related genes.•NolA functions as a dominated transcriptional activator to activate T3SS-related genes and EPS-related genes.•Efficient symbiosis of CCBAU51778 with mung bean rather than peanut relies on fucosylated NFs and intact T3SS.