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Genetic characterization of the hmp locus, a chemotaxis‐like gene cluster that regulates hormogonium development and motility in N ostoc punctiforme
Author(s) -
Risser Douglas D.,
Chew William G.,
Meeks John C.
Publication year - 2014
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.12552
Subject(s) - biology , locus (genetics) , motility , chemotaxis , mutant , microbiology and biotechnology , secretion , gene , flagellum , genetics , biochemistry , receptor
Summary Filamentous cyanobacteria are capable of gliding motility, but the mechanism of motility is not well defined. Here we present a detailed characterization of the hmp locus from N ostoc punctiforme , which encodes chemotaxis‐like proteins. Deletions of hmpB , C , D and E abolished differentiation of hormogonia under standard growth conditions, but, upon addition of a symbiotic partner exudate, the mutant strains differentiated hormogonium‐like filaments that lacked motility and failed to secrete hormogonium specific polysaccharide. The hmp locus is expressed as two transcripts, one originating 5′ of hmpA and encompassing the entire hmp locus, and the other 5′ of hmpB and encompassing hmpBCDE . The CheA ‐like HmpE donates phosphate to its own C ‐terminal receiver domain, and to the CheY ‐like HmpB , but not to the PatA family CheY ‐like HmpA . A GFP ‐tagged variant of each hmp locus protein localized to a ring adjacent to the septum on each end of the rod‐shaped cell. Immunofluorescence demonstrated that PilA localizes to a ring at the junction between cells. The phenotype of the deletion strains, and the localization of the Hmp proteins and the putative PilA protein to rings at the cell junctions are consistent with the hypothesis that these proteins are part of the junctional pore complex observed in a number of filamentous cyanobacteria.