Abstract
psbD contains a blue-light-responsive promoter (psbDLRP), differentially recognized by SIG5, a nuclear-encoded sigma factor of PEP. SIG5 transcription is induced by weak blue-light (5 μmolm-2s-1) via cryptochromes in Arabidopsis. Besides the weak blue-light, psbDLRP activation, however, requires blue light non-specific illumination at high intensity. Here we examine how these two distinct lights are involved in psbDLRP activation. SIG5 transcript abundance increased to a constant level at 120 min after blue-light illumination (5 μmolm-2s-1) with 30-min induction time, while no transcript from psbDLRP was detected. Further illumination of the resulting plants with red-light (50 μmolm-2s-1) immediately induced psbD transcription, which was stimulated by DBMIB. These results indicate that PEP assembled with SIG5 transcribes from psbDLRP, only when plastoquinone pool is reduced by photosynthetic electron transport. It is likely psbD transcription is regulated via a blue-light signal transduction pathway in nucleus and the redox state in chloroplasts.
