UC San Diego

TZP is a single copy gene in Arabidopsis with orthologs in many other plant species. It encodes a unique protein with both a PLUS3 domain and two tandem zinc knuckle domains, which have been implicated in nucleic acid and protein binding. When overexpressed, it has a morning-specific hypocotyl elongation phenotype in blue light and acts downstream of photoreceptors and the circadian clock, but not much is known about its function or protein stability. Some work has been done to determine what proteins interact with TZP, how its localization changes under different light conditions and what functions its domains may serve.

The goals of my project were to explore how TZP protein levels are affected by different light conditions and in different mutant backgrounds as well as to investigate whether yeast two hybrid analysis could reveal any new interactions of TZP with proteins that can affect gene expression, in the hopes of shedding some light on its function. TZP was shown to accumulate most significantly after exposure to blue light, due in part to increased stability of a protein that appears to be targeted for proteasome degradation in the dark. Components of the blue light signaling pathway were shown to be important for stability in blue light and/or degradation in the dark. Yeast two hybrid analysis revealed interactions with some known EAR motif associated corepressors (SAP18 and TPL) as well as with proteins involved in miRNA processing (SERRATE and HYL1) and with the blue light receptor LKP2.