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. The plant Arabidopsis thaliana contains three genes LRB1, LRB2, and LRB3 (Light-Response BTB 1, 2, and 3) that encode similar proteins functioning as target adaptors in E3 ubiquitin-ligase complexes. These complexes select target proteins for degradation. Plants containing mutations in the LRB1 and 2 genes are hypersensitive to red light due to reduced degradation of phytochromes, receptors for red and far-red light. Initial investigation of plants with disruption of the LRB3 gene suggested it does not participate in red-light response like LRB1 and 2. Previously, the laboratory performed genetic screens to identify enhancer mutations which exaggerate the effect of the LRB1/LRB2 mutations. Two of these enhancer mutations are in the Phytochrome B gene. Each of the mutations increases sensitivity to red light and in each case this hypersensitivity is increased when LRB1 and LRB2 are disrupted. To further investigate whether LRB3 might play a role in red light response, we created a line with one of the enhancer mutations in combination with disruption of LRB3. Data from analysis of these mutants will be presented.
