Determining the role of the amino terminal portion of the Light Regulating BTB E3 ligase in Arabidopsis thaliana

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