A major facilitator superfamily protein, HepP, is involved in formation of the heterocyst envelope polysaccharide in the cyanobacterium Anabaena sp. Strain PCC 7120

Rocío López-Igual, Sigal Lechno-Yossef, Qing Fan, Antonia Herrero, Enrique Flores*, C. Peter Wolk

*Corresponding author for this work

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Some filamentous cyanobacteria such as Anabaena sp. strain PCC 7120 produce cells, termed heterocysts, specialized in nitrogen fixation. Heterocysts bear a thick envelope containing an inner layer of glycolipids and an outer layer of polysaccharide that restrict the diffusion of air(including O2) into the heterocyst. Anabaena sp. mutants impaired in production of either of those layers show a Fox- phenotype (requiring fixed nitrogen for growth under oxic conditions). We have characterized a set of transposon-induced Fox- mutants in which transposon Tn5-1063 was inserted into the Anabaena sp. chromosome open reading frame all1711 which encodes a predicted membrane protein that belongs to the major facilitator superfamily (MFS). These mutants showed higher nitrogenase activities under anoxic than under oxic conditions and altered sucrose uptake. Electron microscopy and alcian blue staining showed a lack of the heterocyst envelope polysaccharide (Hep) layer. Northern blot and primer extension analyses showed that, in a manner dependent on the nitrogen-control transcription factor NtcA, all1711 was strongly induced after nitrogen step-down. Confocal microscopy of an Anabaena sp. strain producing an All1711-green fluorescent protein (All1711-GFP) fusion protein showed induction in all cells of the filament but at higher levels in differentiating heterocysts. All1711-GFP was located in the periphery of the cells, consistent with All1711 being a cytoplasmic membrane protein. Expression of all1711 from the PglnA promoter in a multicopy plasmid led to production of a presumptive exopolysaccharide by vegetative cells. These results suggest that All1711, which we denote HepP, is involved in transport of glycoside(s), with a specific physiological role in production of Hep.

Original languageEnglish (US)
Pages (from-to)4677-4687
Number of pages11
JournalJournal of bacteriology
Volume194
Issue number17
DOIs
StatePublished - Sep 1 2012

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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