Rose Weisshaar with Xiaohua Zheng and Dr. Richard Vierstra

Department of Genetics, UW-Madison

Arabidopsis thaliana is touted as a model organism for current plant research, because of its small, five-chromosome genome (entirely sequenced in 2000), its rapid lifecycle, and its habit of self-fertilizing.

The process of transforming the plant’s genome is well established. This study made use of select mutants to further investigate the specific functions of various F-Box proteins. F-Box proteins are part of a cooperative triad of E3 ubiquitin ligases SCF complex. This conglomerate protein targets, on the F-Box domain, specific cellular proteins for ubiquitination and subsequent degradation by the 26S proteasome. The Arabidopsis genome encodes for some 500 distinct F-Box proteins--up to 500 different proteins could be targeted by the various SCF complexes. This study seeks to connect particular F-Box proteins to specific targets through phenotypic analysis of plants homozygous for T-DNA insertions in individual F-Box genes.

Seeds from segregation populations of 37 mutant plant lines were grown and then genotyped to identify plants homozygous for the desired mutation. Eighteen homozygous plant lines (16 distinct F-Box genes) were transferred to soil and grown alongside wild-type plants. The homozygous plants and wild-type plants were then compared to detect any phenotypic abnormalities. Under the growth conditions employed, no abnormalities were observed. This result could be explained in two ways: 1) degradation of the target protein is not essential under normal growth conditions, or 2) redundancy in the genome has mitigated the impact of the "knockout" mutation. We propose next to 1) apply a variety of stress conditions to the progeny of the experimental plants, and 2) cross different knockouts to produce "double knockouts," which may eliminate possible gene redundancy.