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Motility control through an anti‐activation mechanism in Agrobacterium tumefaciens
Author(s) -
Alakavuklar Melene A.,
Heckel Brynn C.,
Stoner Ari M.,
Stembel Joseph A.,
Fuqua Clay
Publication year - 2021
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.14823
Subject(s) - biology , agrobacterium tumefaciens , motility , flagellum , mutant , microbiology and biotechnology , periplasmic space , gene , regulator , genetics , agrobacterium , transformation (genetics) , escherichia coli
Many bacteria can migrate from a free‐living, planktonic state to an attached, biofilm existence. One factor regulating this transition in the facultative plant pathogen Agrobacterium tumefaciens is the ExoR‐ChvG‐ChvI system. Periplasmic ExoR regulates the activity of the ChvG‐ChvI two‐component system in response to environmental stress, most notably low pH. ChvI impacts hundreds of genes, including those required for type VI secretion, virulence, biofilm formation, and flagellar motility. Previous studies revealed that activated ChvG‐ChvI represses expression of most of class II and class III flagellar biogenesis genes, but not the master motility regulator genes visN , visR , and rem . In this study, we characterized the integration of the ExoR‐ChvG‐ChvI and VisNR‐Rem pathways. We isolated motile suppressors of the non‐motile Δ exoR mutant and thereby identified the previously unannotated mirA gene encoding a 76 amino acid protein. We report that the MirA protein interacts directly with the Rem DNA‐binding domain, sequestering Rem and preventing motility gene activation. The ChvG‐ChvI pathway activates mirA expression and elevated mirA is sufficient to block motility. This study reveals how the ExoR‐ChvG‐ChvI pathway prevents flagellar motility in A. tumefaciens . MirA is also conserved among other members of the Rhizobiales suggesting similar mechanisms of motility regulation.