Light is important for plants as an energy source for photosynthesis, as a measure of day/night and seasonal cycles, and as information about the surrounding environment. For this reason, plants have evolved a sophisticated set of pathways to detect and respond to light, which allows them to adjust their development in response to changing conditions. Red and far-red light are detected by photoreceptors called phytochromes. A genetic screen for Arabidopsis thaliana mutants altered in red-light response conducted by the Gingerich lab identified mutations in PHYB, the gene encoding the major phytochrome involved in red-light responses. We have found that one of these mutations, which is predicted to alter a single amino acid in the phyB protein, increases sensitivity to not only red-light but also blue. Furthermore, this increased blue sensitivity is exacerbated when the genes LRB1 and LRB2 (which encode proteins functioning in complexes that initiate red-induced degradation of the phytochromes) are disrupted. This suggests a previously unrecognized interaction between blue-light response and the red-light phytochrome response pathway. Characterization of the blue-light response of this mutant will be presented.
