Abstract
To elucidate the mechanism of plant responses to the shade, we have previously identified a promoter trap line in which the GUS reporter gene expression in hypocotyls is regulated by the end-of-day far-red light and auxin treatments (Tanaka et al., PCP 43:1171, 2002). Examination of the photoreceptive sites in this response revealed the signaling from phytochromes in cotyledons to the target genes in hypocotyls. To identify molecular components of this inter-organ signaling, we screened for mutants showing different patterns of GUS expression. We found 2 mutant lines which showed morphological phenotype in darkness. Both the mutants had shorter hypocotyls in complete darkness compared to the parental line. However concerning the GUS expression, two lines showed an opposite phenotype. One line, named as reg1, showed lower GUS expression in darkness whereas the other, named as rig1, showed higher expression. We also observed abnormal response to end-of-day far-red light treatments in rig1.
