A hormogonium regulating locus, hrmUA, of the cyanobacterium Nostoc punctiforme strain ATCC 29133 and its response to an extract of a symbiotic plant partner Anthoceros punctatus

• Published in: Molecular plant-microbe interactions Vol. 10; no. 2; pp. 280 - 289
• Main Authors: COHEN, M. F, MEEKS, J. C
• Format: Journal Article
• Language: English
• Published: St Paul, MN APS Press 01-03-1997; The American Phytopathological Society
• Subjects: adn recombinado; adn recombine; Amino Acid Sequence; anatomia de la planta; anatomie vegetale; Biological and medical sciences; bryophyta; chemical composition; Chromosome Mapping; Cloning, Molecular; composicion quimica; composition chimique; Cyanobacteria - genetics; DNA Transposable Elements; expresion genica; expression des genes; extractos vegetales; extrait d' origine vegetale; fenotipos; Fundamental and applied biological sciences. Psychology; gene; gene expression; genes; Genes, Bacterial; hormogonium differentiation; induced mutation; loci; locus; Molecular Sequence Data; multicopy inhibition; mutacion; mutacion inducida; Mutagenesis, Insertional; mutation; mutation provoquee; nostoc; Nostoc sp. strain ATCC 29133; nucleotide sequence; omega-npt cassette; oxidoreductases; oxidorreductasas; oxydoreductase; Parasitism and symbiosis; phenotype; phenotypes; plant anatomy; plant extracts; Plant physiology and development; plant-cyanobacterial signaling; Plants - microbiology; proteinas; proteine; proteins; recombinant dna; secuencia nucleotidica; sequence nucleotidique; simbiontes; simbiosis; symbionts; symbiose; Symbiosis; Symbiosis - genetics; symbiote; symbiotic cyanobacterium; Transposition; Regulation(control); Symbionte; Gene; Anthocerotae; Vegetal microorganism relation; Bryophyta; Differentiation
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/MPMI.1997.10.2.280

Transposon-generated mutant strain UCD 328 of Nostoc punctiforme strain ATCC 29133 has a phenotype of an increased sensitivity to a hormogonium-inducing factor exuded by a symbiotic plant partner, Anthoceros punctatus, and an initial increased hormogonium-dependent infection of the plant. Sequence analysis showed that the transposition site in strain UCD 328 lies within a 1,251-bp open reading frame (ORF), designated hrmA, that displays no significant similarity to known database sequences. A second, 837-bp ORF (hrmU) ends 2 bp 5 from the start of hrmA and has the signature sequences belonging to a family of NAD(P)H-dependent oxidoreductases. Strains having insertional mutations in hrmU or hrmA reproduce the strain UCD 328 phenotype. Transcriptional fusions of luxAB to hrmU or hrmA show an 8- to 10-fold peak increase in luciferase activity 13 to 20 h after the start of incubation in the presence of an aqueous extract of A. punctatus. A promoter induced by the extract was deduced to be between 2.0 to 3.4 kb from the translational start of hrmU. A multicopy plasmid that contains hrmUA within a 6.2-kb fragment conferred an increased infection phenotype on wild-type N. punctiforme 29133. This plasmid and another plasmid containing 4.4 kb of DNA5' of the transposition site prevented extract-dependent induction of hrmA-luxAB transcription in strain UCD 328, implicating titration of some trans-activator(s) by the cloned fragments. We hypothesize a role for hrmUA in the inhibition of hormogonium formation by the metabolism of an unknown hormogonium-regulating metabolite.