Sequence Analysis of Alpha Crystalline Domain of Small Heat Shock Proteins (sHSPs) Family in Different Plant Species

Abstract

Alpha crystalline domain (ACD/HSP20) proteins belong to a diverse family of molecular chaperones which play a central role in different plant species under stress condition. We have studied about 100 sequences having alpha crystalline domains from Arabidopsis thaliana, Zea mays, Oryza sativa, Sorghum bicolor, and Cicer arietinum. High residual conservancy in ACD domain and variation in the N-terminal region were observed in these plant species. We also observed the orphan genes like transcripts. Phylogenetic studies classified them into three well-categorized clades with eleven subgroups/families according to their amino acid sequences of a conserved domains. Duplication events and basic to the intricate pattern of conservancy within the conserved domain of subgroups existed. Exon/intron boundaries and cellular localization pattern further support the phylogenetic-based categorization of these genes. About 50% of them are cytoplasm-specific while the others are chloroplast-, mitochondria-, and extracellular matrix-specific tags. We also detected the conserved patterns of functional motifs within the coding sequences of heat shock protein genes of above-mentioned plant species. Overall expression pattern was found to be much higher in Arabidopsis, rice, and maize under heat, salt, and drought stress, respectively, than cold stress while homogenous expression was observed at tissue-specific level. These results would be useful to understand the further functional characterization of small heat shock proteins.