Poster: Signaling, cell-to-cell

Abs # 441: CaMs and CMLs as potential mediators of calcium signaling in Arabidopsis

Presenter:	McCormack, Elizabeth , lizmctx98@yahoo.com
Authors	McCormack, Elizabeth  (A)   Braam, Janet  (A)
Affiliations:	(A): Rice University, Biochemistry and Cell Biology

Calcium Signaling has been proposed to be involved in coordinating cellular responses to developmental, hormonal, biotic, and abiotic stimuli. The classical calcium sensor is calmodulin (CaM), which regulates activity of its protein targets in a calcium-dependent manner. Sequencing of the Arabidopsis genome reveals a large family of genes encoding potential calcium sensors comprising 7 CAMs and 50 CAM-Like (CML) members. (McCormack and Braam, 2003. New Phytologist, 159: 585-598.) The proteins encoded by these 57 genes are composed mostly, if not entirely, of the EF-hand calcium-binding motif and share between 16-100% amino acid sequence identity with Arabidopsis CaM2, a typical CaM. Sequence divergence among members of the CaM/CML family has resulted in altered EF-hand number, organization, and predicted functional capacity. Differences in gene and protein structure as well as expression behavior may indicate that each CaM or CML has a distinct role in responding to stress. We aim to determine the physiological function of the Arabidopsis CAM and CML family through analysis of gene expression profiles and characterization of cam/cml mutants. We detect CAM/CML expression in discrete organs and in response to various environmental stimuli. We have isolated T-DNA insertion mutants in 14 of the CAM/CMLs. We are also pursuing mutations that cause amino acid residue changes in CML12/TCH3 to determine the effect of minor changes in protein structure or calcium affinity on protein function. Research supported by NSF (IBN0313432 and IBN9982654 to J.B.) and, in part, by NIH (Biotechnology Training Grant T32-GM08362 to E.M.).