Action spectrum for expression of the high intensity light-inducible Lhc-like gene Lhl4 in the green alga Chlamydomonas reinhardtii.
Lhl4 encodes a distant relative of light-harvesting Chl-a/b proteins in the green alga Chlamydomonas reinhardtii. Lhl4 mRNA markedly accumulated within 30 min after illumination and in proportion to the light intensity up to a fluence rate much higher than that required for photosynthesis. The high intensity light (HL)-induced accumulation of Lhl4 mRNA required continuous illumination, and the mRNA level rapidly decreased when the cells were placed in the dark. HL only slightly stabilized the mRNA, suggesting that the HL-induced expression of the Lhl4 gene is primarily regulated at the level of transcription. Blue light was more effective for inducing Lhl4 gene expression than green or red light, and far-red light had no effect. The action spectrum for Lhl4 gene expression was examined at wavelengths between 325 and 775 nm using the Okazaki Large Spectrograph. The obtained spectrum showed a distinct peak in the blue region (450 nm) and a shoulder in the UV-A region (375 nm). The curve in the spectrum rose steeply in the short wavelength UV region. In addition, we observed two minor peaks in the green (575 nm) and the red (675 nm) regions. The action spectrum suggests that a blue/UV-A light photoreceptor with a flavin-based chromophore participates in the HL response of Lhl4 gene expression. However, the hypersensitivity to near UV-B light suggests the involvement of an unidentified UV light perception system in the expression of the Lhl4 gene.
Teramoto
Haruhiko
H
Laboratory for Photo-Biology (1), Photodynamics Research Center, RIKEN, Sendai, Japan. teramoto@riken.or.jp
Ishii
Asako
A
Kimura
Yukihiro
Y
Hasegawa
Koji
K
Nakazawa
Shigeaki
S
Nakamura
Takanori
T
Higashi
Sho-ichi
S
Watanabe
Masakatsu
M
Ono
Taka-aki
TA
D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects*; D003624:Darkness; D005786:Gene Expression Regulation; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000235:genetics* / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D020871:RNA Stability / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
D020418:Algal Proteins; D045342:Light-Harvesting Protein Complexes; D015800:Protozoan Proteins; D012333:RNA, Messenger