title: Expression of the nifH gene of a Herbaspirillum endophyte in wild rice species: daily rhythm during the light-dark cycle.
abstract: The expression of nitrogenase genes of Herbaspirillum sp. B501 associated in shoot (leaf and stem) of wild rice, Oryza officinalis, was studied by means of reverse transcription-PCR (RT-PCR) targeted at the nifH gene. RT-PCR analyses indicate that nifH transcript was detected exclusively from nitrogen-fixing cells of gfp-tagged strain B501gfp1 in both free-living and endophytic states by using a constitutive gfp gene transcript as a positive control. Transcription of nifH and nitrogen fixation in free-living cells were induced maximally at a 2% O2 concentration and repressed in free air (21% O2). nifH transcription was monitored in the endophytic cells by using total RNA extracted from B501gfp1-inoculated wild rice plants during daily light-dark cycles. The level of nifH transcription in planta varied dramatically, with a maximum during the light period. Moreover, the light radiation enhanced nifH expression even in free-living cells grown in culture. These results suggest that in planta nitrogen fixation by the endophyte shows a daily rhythm determined by the plant's light environment.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Mu
authors.initials: M
authors.lastname: You
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Nishiguchi
authors.forename: Asami
authors.initials: A
authors.lastname: Saito
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Isawa
authors.forename: Hisayuki
authors.initials: H
authors.lastname: Mitsui
authors.forename: Kiwamu
authors.initials: K
authors.lastname: Minamisawa
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001683:Biological Clocks; D002940:Circadian Rhythm; D016384:Consensus Sequence; D017931:DNA Primers; D003624:Darkness; D042803:Herbaspirillum / Q000201:enzymology* / Q000254:growth & development / Q000528:radiation effects; D008027:Light; D008969:Molecular Sequence Data; D012275:Oryza / Q000382:microbiology*; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
chemical_list: D017931:DNA Primers; D010088:Oxidoreductases; C029130:nitrogenase reductase