Electronic Thesis and Dissertation Repository


Master of Science




Dr. Vojislava Grbic


The HULK gene family participates in regulation of both flowering time and development in the plant Arabidopsis thaliana. The proteins encoded by these genes share conserved domain structures including a proline-rich region (PRR) in the carboxyl-terminus. Based on sequence analysis and the presence of a proline-rich domain, it has been suggested that the HULKs are putative transcription factors in which HUA2 is known to regulate several late-flowering genes: FLC, FLM and MAF2.

To investigate the putative transcriptional activation domain in the carboxyl-terminus of the HULKs, full-length HULKs and deletion constructs were 3-AT titrated in yeast-one hybrids. It was found that the transcriptional activity varied between both the full-length and carboxyl-terminus of the HULKs as well as between the HULKs themselves. However, it was established that HULK2 carried the strongest transcriptional activation domain, which was active in both the full-length protein and when expressed as just in the carboxyl-terminus.

A domain swap was then performed with HULK2’sPRR and HULK3’s significantly weaker PRR to see if the transcriptional activity observed in HULK2 was localised to the PRR. While it was established that the PRR found at the carboxyl-terminus did contribute to the transcriptional activity, it was determined that the domain is not solely responsible for the transcriptional activity. The data suggests that there are multiple transcriptional activation domains working in tandem in the HULKs.