Expression of the nifH gene of a Herbaspirillum endophyte in wild rice species: daily rhythm during the light-dark cycle.
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.
You
Mu
M
Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan.
Nishiguchi
Tomohiro
T
Saito
Asami
A
Isawa
Tsuyoshi
T
Mitsui
Hisayuki
H
Minamisawa
Kiwamu
K
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
D017931:DNA Primers; D010088:Oxidoreductases; C029130:nitrogenase reductase