Poster: Temperature responses

Abs # 112: Mutants in the Arabidopsis SAC9 gene are constitutively cold-acclimated and overaccumulate PtdIns(4,5)P₂

Presenter:	Williams, Mary E., mary_williams@hmc.edu
Authors	Williams, Mary E. (A)   Torabinejad, Javad  (B) (C)  Cohick, Evan  (A)   Nguyen, Vi  (A)   DeWald, Daryll B. (B)
Affiliations:	(A): Harvey Mudd College (B): Utah State University (C): Virgnina Tech

We isolated an Arabidopsis mutant with characteristics of a constitutive cold-acclimation response including dwarfism, a prostrate growth habit and freezing tolerance. At room temperature, the mutant expresses several cold-induced genes including CBF1 and CBF2. The mutant is partially freezing tolerant without prior cold-acclimation. The mutant accumulates anthocyanin, which together with its prostrate growth suggests it is light-sensitive. Growth in dim light reverses the anthocyanin accumulation and prostrate growth, but not the dwarfism. The affected gene, SAC9 (At3g59770), encodes a putative phosphoinositide phosphatase. The SAC9 protein is different from other SAC domain proteins in several ways including the presence of a WW protein-interaction domain within the SAC domain. The rice and Arabidopsis SAC9 proteins are closely related, but SAC9 appears to be a plant-specific protein. HPLC studies show that sac9 mutants overaccumulate PtdIns (4,5)P₂, as do cold-treated wild-type plants, suggesting that PtdIns (4,5)P₂ has a role in the cold-signaling pathway.