Poster: Protein turnover

Abs # 818: The Role of AIP6 in the Control of the Arabidopsis Post-Germinative Developmental Arrest

Presenter:	Host, Laurie A, laurieh1@umbc.edu
Authors	Host, Laurie A (A)   Bustos, Mauricio  (A)
Affiliations:	(A): University of Maryland - Baltimore County

Higher plants possess the ability to facultatively arrest or delay development at multiple points during their life cycle, a common survival strategy for when conditions are not permissive for growth. In Arabidopsis thaliana, developmental arrest may be induced in young seedlings between 2 and 3 days after germination. During this time window, seedlings that are desiccation stressed or exposed to abscisic acid (ABA) arrest development. ABI3, ABI5, and other ABA-insensitive (ABI) proteins are involved in ABA sensing, and at least one of these factors, ABI5, is required for the onset of ABA-induced developmental arrest. However, the molecular mechanisms of how progression through this developmental arrest checkpoint are regulated have not yet been elucidated. Previously, our laboratory conducted a yeast two-hybrid screen of an Arabidopsis whole seedling cDNA library that uncovered interactions between ABI3 and several ABI3 Interactive Proteins (AIPs). The deduced amino acid sequence of one of these proteins, AIP6, predicts the presence of a RING-H2 domain, a motif found in many eukaryotic E3 ubiquitin protein ligases. E3 enzymes catalyze the covalent attachment of ubiquitin tags to cellular proteins committing them for degradation by the 26S proteasome. Interestingly, the highest levels of AIP6 mRNA occur during the first 3 days of development after germination, at a time when ABI3 protein normally disappears from the seedling. These observations led us to propose that AIP6 protein is responsible for ABI3 degradation, and that it may be necessary to release young seedlings from developmental arrest. Multiple strategies of plant molecular biology, protein purification, and protein identification will be used to test this hypothesis.