Poster: Intracellular Signaling

Abs # 849: An Arabdopsis mutant in a novel Sac domain/phosphoinositide phosphatase-like gene

Presenter:	Williams, Mary E, Mary_Williams@hmc.edu
Authors	Williams, Mary E (A)   Parker, Katherine  (A)   Pava, Justin  (A)   Lee, Sung-Eun  (A)
Affiliations:	(A): Harvey Mudd College

We have identified an EMS-generated Arabidopsis mutant that underproduces lateral roots and has altered hormone sensitivities. The mutant grows slowly, has short primary roots and few short lateral roots. The shoot is small and the tiny leaves accumulate a large amount of anthocyanin. We mapped the mutation to a 200 kb region and then screened through SALK T-DNA insertion mutants of genes in this interval. We identified an insert line with the identical phenotype to our original isolate, and genetic complementation shows that the two are allelic. The mutated gene is predicted to encode a 5 kb mRNA (a full length cDNA has been identified). The predicted 1616 amino acid protein has an N-terminal phosphoinositide phosphatase/Sac domain, suggesting a role in the degradation of phosphatidylinositol phosphate signals. In yeast and plants, phosphatidylinositol phosphates accumulate during osmotic stress. The Arabidopsis genome encodes four other Sac-domain proteins, but this one is unique in the presence of a WW domain similar to those found in ubiquitin ligases immediately adjacent to the Sac domain. The Arabidopsis gene and the rice homologue are 65% amino acid conserved throughout their entire length, but 80% conserved through the Sac and WW domains. Our continuing molecular, genetic and physiological studies of these mutants will be presented.