Abstract
Dynamic behavior and light strength dependency of the blue light induced SIG5 transcription were examined in Arabidopsis thaliana, being compared with other five SIG genes. Transcription of SIG1 and SIG5 in wild type plants was induced by blue-light with the induction time of 30 min and the threshold intensity of 2 μmol/m2s. The SIG1 transcripts accumulated after 90 min illumination kept constant between 2 and 50 μmol/m2s. While that of SIG5 kept constant between 2 and 10 μmol/m2s, but increased with increasing light-intensity beyond 10 μmol/m2s. In the cryptochrome mutant, the SIG5 transcription was not induced by blue-light at all. While the SIG1 transcripts were induced at 30% of the wild-type. These results indicate that cryptochrome mediates the transcription of SIG5 via two pathways differently responding to weak and strong blue-light, and cryptochrome-dependent and independent pathways are involved in the blue light induced SIG1 transcription.
