Identification of a light-regulated protein kinase activity from seedlings of Arabidopsis thaliana.
Protein kinase transduction pathways are thought to be involved in light signaling in plants, but other than the photoreceptors, no protein kinase activity has been shown to be light-regulated in vivo. Using an in-gel protein kinase assay technique with histone H III SS as an exogenous substrate, we identified a light-regulated protein kinase activity with an apparent molecular weight ca 50 kDa. The kinase activity increased transiently after irradiation of dark-grown seedlings with continuous far red light (FR) and blue light (B) and decreased after irradiation with red light (R). The maximal activation was achieved after 30 min to 1 h with FR or B. After irradiation times longer than 2 h, the kinase activity decreased to below the sensitivity level of the assay. In Arabidopsis mutants lacking either the photoreceptors phytochrome A, phytochrome B or the blue-light receptor cryptochrome 1, kinase activity was undetectable, whereas in the photomorphogenic mutants cop1 and det1 the kinase activity was also observed in the absence of light signals, though still stimulated by B and FR. Interestingly, the R inhibition of the kinase activity was lost in the mutant hy5. Pretreatment with cycloheximide blocked the kinase activity.
Malec
Przemyslaw
P
Department of Plant Sciences, Tel Aviv University, Israel.
Yahalom
Avital
A
Chamovitz
Daniel A
DA
D017360:Arabidopsis / Q000201:enzymology*; D008027:Light; D055537:Light Signal Transduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D010940:Plant Proteins / Q000302:isolation & purification / Q000378:metabolism / Q000528:radiation effects; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism / Q000528:radiation effects*; D036226:Seedlings / Q000201:enzymology
D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins; D011494:Protein Kinases