University of Wisconsin-Eau Claire Pewaukee, Wisconsin
Body of Abstract: Red light and far-red light are detected by phytochrome photoreceptors in Arabidopsis thaliana. LRB1 and LRB2 (Light-Response BTB 1 and 2) are two genes in Arabidopsis that encode functionally redundant BTB (Broad-complex, Tramtrack, and Bric-a-brac) domain-containing proteins that act as target adapters in BTB/Cullin 3 E3 ubiquitin-ligase complexes that control degradation of phytochromes. Disruption of LRB1 and 2 results in a red-light hypersensitive phenotype as a result of reduced phytochrome degradation. To identify mutations which affect red-light responses in Arabidopsis, we conducted genetic enhancer and suppressor screens with the lrb1 lrb2 mutants. We have identified the putative suppressor/enhancer mutations in several of the lines and in each case they are within the coding region for phyB, the major red-light receptor in Arabidopsis. Recent work in the lab has focused on characterizing two of the enhancer mutant lines. In each the enhancer mutation is predicted to result in a single amino acid change in the phyB protein. In the absence of the background lrb1and lrb2 mutations the effect of the PHYB point mutations are greatly reduced, which demonstrates that our screen, with its reduced light-dependent phytochrome degradation background, has the power to identify mutations which produce subtle effects on phyB function. We are completing the backcrossing process for these lines and are beginning/repeating detailed phenotypic analyses. One of the lines also has a blue-light hypersensitive phenotype and we are currently conducting analyses to determine if that phenotype is linked to the phyB mutation.