Comparative proteomic analysis revealing ActJ-regulated proteins in Sinorhizobium meliloti

ALBICORO FJ; VACCA C.; CAFIERO JH; DRAGHI WO; MARTINI MC; GOULIAN M; LAGARES A; DEL PAPA MF

JOURNAL OF PROTEOME RESEARCH

AMER CHEMICAL SOC

Lugar: Washington; Año: 2023

1535-3893

To adapt to different environmental conditions Sinorhizobium meliloti relies on finely tuned regulatory networks, most of them unexplored to date. We recently demonstrated that deletion of the two-component system ActJK renders an acid-vulnerable phenotype in S. meliloti and negatively impacts on bacteroid development and nodule occupancy, as well. To fully understand the role of ActJ in acid tolerance, S. meliloti wild-type and S. meliloti ΔactJ proteomes were compared in the presence or absence of acid stress by nanoflow ultrahigh-performance liquid chromatography coupled to mass spectrometry. The analysis demonstrated that proteins involved in the synthesis of exopolysaccharides (EPS) were notably enriched in ∆actJ cells in acid pH. Total EPS quantification further revealed that although EPS production was augmented at pH 5.6 in both the ΔactJ and the parental strain, the lack of ActJ significantly enhanced this difference. Moreover, several efflux pumps were found downregulated in the ΔactJ strain. Promoter fusion assays suggested that ActJ positively modulated its own expression in an acid medium but not at neutrality. The results presented here identifies several ActJ-regulated genes in S. meliloti, highlighting key components associated with ActJK regulation that will contribute to a better understanding of rhizobia adaptation to acid stress