title: Genes encoding calmodulin-binding proteins in the Arabidopsis genome.
abstract: Analysis of the recently completed Arabidopsis genome sequence indicates that approximately 31% of the predicted genes could not be assigned to functional categories, as they do not show any sequence similarity with proteins of known function from other organisms. Calmodulin (CaM), a ubiquitous and multifunctional Ca(2+) sensor, interacts with a wide variety of cellular proteins and modulates their activity/function in regulating diverse cellular processes. However, the primary amino acid sequence of the CaM-binding domain in different CaM-binding proteins (CBPs) is not conserved. One way to identify most of the CBPs in the Arabidopsis genome is by protein-protein interaction-based screening of expression libraries with CaM. Here, using a mixture of radiolabeled CaM isoforms from Arabidopsis, we screened several expression libraries prepared from flower meristem, seedlings, or tissues treated with hormones, an elicitor, or a pathogen. Sequence analysis of 77 positive clones that interact with CaM in a Ca(2+)-dependent manner revealed 20 CBPs, including 14 previously unknown CBPs. In addition, by searching the Arabidopsis genome sequence with the newly identified and known plant or animal CBPs, we identified a total of 27 CBPs. Among these, 16 CBPs are represented by families with 2-20 members in each family. Gene expression analysis revealed that CBPs and CBP paralogs are expressed differentially. Our data suggest that Arabidopsis has a large number of CBPs including several plant-specific ones. Although CaM is highly conserved between plants and animals, only a few CBPs are common to both plants and animals. Analysis of Arabidopsis CBPs revealed the presence of a variety of interesting domains. Our analyses identified several hypothetical proteins in the Arabidopsis genome as CaM targets, suggesting their involvement in Ca(2+)-mediated signaling networks.
authors.affiliation: Department of Biology and Program in Cell and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, USA. reddy@lamar.colostate.edu
authors.forename: Vaka S
authors.initials: VS
authors.lastname: Reddy
authors.forename: Gul S
authors.initials: GS
authors.lastname: Ali
authors.forename: Anireddy S N
authors.initials: AS
authors.lastname: Reddy
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000235:genetics*; D018076:DNA, Complementary / Q000378:metabolism; D019992:Databases as Topic; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D018745:Genome, Plant; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D018076:DNA, Complementary; D020033:Protein Isoforms; D012313:RNA; D002118:Calcium