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Title: Structure-function analysis of the transcriptional regulator TZP in Arabidopsis thaliana
Author: Davidson, Mhairi Louise Hope
ISNI:       0000 0005 0286 8679
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 2021
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Light signalling is vital to the control of development in plants. TANDEM ZINC-FINGER PLUS3 (TZP) is a transcriptional regulator which has been shown to mediate light-responsive developmental transitions in Arabidopsis. During photomorphogenesis for example, hypocotyl growth is positively regulated by TZP in low blue light. Furthermore, TZP localises to transcriptionally active nuclear bodies. This thesis aims to understand the structure-function relationship of TZP in blue-light mediated hypocotyl growth. Hypocotyl elongation-promoting genes are co-regulated by TZP and its interacting partner the transcription factor ZFHD10 in blue light. TZP also interacts with the blue light photoreceptor cry1 in planta. TZP contains tandem zinc-fingers (ZFs) and a Plus3 domain at the C-terminus. Deletion analysis suggests the TZPZF-Plus3 region is sufficient to rescue the short hypocotyl phenotype of the tzp mutant in blue light. Whereas, TZP nuclear body formation requires the N-terminus which has no predicted structure. Within the Plus3 domain, TZP has a putative Ethylene-responsive element binding factor-associated Amphiphilic Repression (EAR) motif. EAR motifs are typically found in active transcriptional repressors, however, TZP does not show repressive activity in a fluorescence-based assay for transcriptional repression. Also, the ability of TZP to promote blue light-mediated hypocotyl elongation is not affected by the absence of the potential EAR motif. In addition to protein structure, post-translational modification of TZP may have a role in regulating hypocotyl growth. SUMOylation is the reversible attachment of a SUMO protein to a lysine within the target protein. In a proteomic analysis for proteins bound to a SUMO1 variant, TZP was identified as a SUMO conjugate when plants undergo heat-stress. The amino acid sequence of TZP contains six SUMOylation sites predicted by two algorithms, one plant-specific. TZP’s role in promoting hypocotyl elongation in blue light is inhibited by the absence of these sites, which indicates SUMOylation may regulate TZP function. Overall, these findings support the relationship between TZP structure and function in the regulation of plant development.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: QH426 Genetics ; QK Botany