title: Clustered genes required for synthesis and deposition of envelope glycolipids in Anabaena sp. strain PCC 7120.
abstract: Photoreduction of dinitrogen by heterocyst-forming cyanobacteria is of great importance ecologically and for subsistence rice agriculture. Their heterocysts must have a glycolipid envelope layer that limits the entry of oxygen if nitrogenase is to remain active to fix dinitrogen in an oxygen-containing milieu (the Fox+ phenotype). Genes alr5354 (hglD), alr5355 (hglC) and alr5357 (hglB) of the filamentous cyanobacterium, Anabaena sp. strain PCC 7120, and hglE of Nostoc punctiforme are required for synthesis of heterocyst envelope glycolipids. Newly identified Fox- mutants bear transposons in nearby open reading frames (orfs) all5343, all5345-asr5349 and alr5351-alr5358. Complementation and other analysis provide evidence that at least orfs all5343 (or a co-transcribed gene), all5345, all5347, alr5348, asr5350-alr5353 and alr5356, but not asr5349, are also required for a Fox+ phenotype. Lipid and sequence analyses suggest that alr5351-alr5357 encode the enzymes that biosynthesize the glycolipid aglycones. Electron microscopy indicates a role of all5345 through all5347 in the normal deposition of the envelope glycolipids.
authors.affiliation: MSU-DOE Plant Research Laboratory and Department of Plant Biology, Michigan State University, East Lansing, MI 48824-1312, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Fan
authors.forename: Guocun
authors.initials: G
authors.lastname: Huang
authors.forename: Sigal
authors.initials: S
authors.lastname: Lechno-Yossef
authors.forename: C Peter
authors.initials: CP
authors.lastname: Wolk
authors.forename: Takakazu
authors.initials: T
authors.lastname: Kaneko
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tabata
mesh_terms: D000595:Amino Acid Sequence; D017033:Anabaena / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D002473:Cell Wall / Q000737:chemistry / Q000648:ultrastructure; D002855:Chromatography, Thin Layer; D004251:DNA Transposable Elements; D005816:Genetic Complementation Test; D016680:Genome, Bacterial; D006017:Glycolipids / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D009154:Mutation; D016366:Open Reading Frames; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D006017:Glycolipids