Genes aotM and trmD Regulate Salt-alkali Tolerance， Antioxidase Activity， and Cell Membrane Oxidative Damage in Rhizobia​

doi:10.13560/j.cnki.biotech.bull.1985.2025-1045

Abstract

Abstract:

Objective The evolved strain Alk_55 was obtained from Rhizobium yanglingense CCBAU 01603 through continuous subculturing. This work aims to investigate the underlying reasons for the significant enhancement of salt-alkali tolerance caused by SNP changes in aotM and trmD in the Alk_55 genome. Method The regulation of salt-alkali tolerance, cell membrane damage, intracellular antioxidant enzyme activity, and reactive oxygen species (ROS) content in rhizobia were assessed, based on two mutants of rhizobia, △aotM and △trmD, created by deleting genes aotM and trmD respectively. Result Mutant △aotM and △trmD had stronger salt-alkali tolerance and reduced sensitivity to salt-alkali stress within a certain concentration range, compared with the wild-type strain. Significantly lower malondialdehyde (MDA) content indicated less lipid peroxidative damage to the cell membrane. Intracellular superoxide dismutase (SOD) and catalase (CAT) activities markedly increased, whereas ROS content significantly decreased. Conclusion Genes aotM and trmD strongly regulate salt-alkali tolerance, intracellular antioxidase activity, and oxidative stress-induced cell membrane damage in rhizobia.

Key words: Rhizobium, aotM, trmD, salt-alkali tolerance, MDA content, antioxidase

LIU Jun-liang, YUAN Xiao-xia, QIAO Mei-ling, YANG Bing-jie, YU Xiu-min, MU Sha-mo-li, JI Zhao-jun. Genes aotM and trmD Regulate Salt-alkali Tolerance， Antioxidase Activity， and Cell Membrane Oxidative Damage in Rhizobia[J]. Biotechnology Bulletin, 2026, 42(8): 323-330.

Figures/Tables 6

Fig. 1 Alignment analysis and conservation of aotM and trmD gene sequences in evolved isolates Alk_55A: Comparison of gene and amino acid sequences of trmD. B: Comparison of gene and amino acid sequences of aotM. C: Phylogenetic tree of trmD gene. D: Phylogenetic tree of aotM gene

Fig. 2 Growth of rhizobia in YMA liquid medium with different concentrations of NaClA: No NaCl. B: Containing 0.5% NaCl. C: Containing 0.6% NaCl. D: Containing 0.7% NaCl; *P<0.05, **P<0.01, ***P<0.001, ****P<0.000 1. The same below

Fig. 3 Growth of rhizobia in YMA liquid medium with different pH valuesA: YMA broth with pH value of 8.12 (containing 100 μL KOH stock solution). B: YMA broth with pH value 8.90 (containing 200 μL KOH stock solution)

Fig. 4 Antioxidant enzyme activity of rhizobiaA: Catalase (CAT) activity. B: Superoxide dismutase (SOD) activity

Fig. 5 MDA contents in the membrane of rhizobia

Fig. 6 Intracellular ROS accumulation in rhizobia

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