3 years ago

Dynamic localization of HmpF regulates type IV pilus activity and directional motility in the filamentous cyanobacterium Nostoc punctiforme

Dynamic localization of HmpF regulates type IV pilus activity and directional motility in the filamentous cyanobacterium Nostoc punctiforme
Parth Italia, Thomas V. Harwood, Jun Sang Park, Yeji Hwang, Jessica Huynh, Alfonso Gonzales, Douglas D. Risser, Vivek K. Pallipuram, Anthony Q. Trieu, Ye Won Cho
Many cyanobacteria exhibit surface motility powered by type 4 pili (T4P). In the model filamentous cyanobacterium Nostoc punctiforme, the T4P systems are arrayed in static, bipolar rings in each cell. The chemotaxis-like Hmp system is essential for motility and the coordinated polar accumulation of PilA on cells in motile filaments, while the Ptx system controls positive phototaxis. Using transposon mutagenesis, a gene, designated hmpF, was identified as involved in motility. Synteny among filamentous cyanobacteria and the similar expression patterns for hmpF and hmpD imply that HmpF is part of the Hmp system. Deletion of hmpF produced a phenotype distinct from other hmp genes, but indistinguishable from pilB or pilQ. Both an HmpF-GFPuv fusion protein, and PilA, as assessed by in situ immunofluorescence, displayed coordinated, unipolar localization at the leading pole of each cell. Reversals were modulated by changes in light intensity and preceded by the migration of HmpF-GFPuv to the lagging cell poles. These results are consistent with a model where direct interaction between HmpF and the T4P system activates pilus extension, the Hmp system facilitates coordinated polarity of HmpF to establish motility, and the Ptx system modulates HmpF localization to initiate reversals in response to changes in light intensity. Many cyanobacteria exhibit twitching or gliding motility powered by type 4 pili (T4P). Using transposon mutagenesis, the gene hmpF, which encodes a novel component of the Nostoc punctiforme Hmp chemotaxis system was identified. HmpF is essential for motility and extension of T4P. Directional reversals were induced by changes in light intensity and preceded by the dynamic localization of HmpF from leading to lagging poles.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/mmi.13761

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