Abstract

Plant growth and development is controlled by the different wavelengths in the electromagnetic spectrum. Phytochrome B (PhyB), a red and far-red light photoreceptor in plants, plays an integral role in shade avoidance, flowering time, seed germination, and de-etiolation. Proper degradation of this photoreceptor is crucial to the function of these processes. Degradation of this protein occurs via the ubiquitin-proteasome system. The light regulating Bric-a-Brac/Tramtrack/Broad Complex (LRB) protein, in conjunction with CUL3, forms an E3 ligase complex which facilitates the attachment of ubiquitin to phytochrome B. Preliminary research has revealed a highly conserved region of the LRB protein near its N-terminus which has not been associated with any function. Our analysis suggests that it may play a role in controlling rubylation which could affect PhyB breakdown. To determine if the LRBs play a role in rubylation, a truncated version of the LRB gene missing this highly conserved region was inserted into a wild type and a lrb1 lrb2 double mutant Arabidopsis thaliana plant. To date, phenotypic and immunoblot analysis of homozygous lines featuring the truncated LRBs suggest that the N-terminal region may play a role in their function. Future analysis of these lines will give insight into the role of this N-terminal region of the LRB’s in phytochrome degradation and the function of its E3 ligase complex.