Identification of HSP20 gene family in wheat and barley and their differential expression profiling under heat stress.

Small heat shock proteins (sHSPs) are chaperones that play an important role in various developmental, biotic and abiotic stresses. The sHSP family possess a conserved domain of approximately 80 to 100 amino acids called alpha-crystalline domain (ACD), flanked by N- and C-terminal regions. Search for complete proteomes and expressed sequenced tag (EST) database of wheat and barley using Hidden Markov Model and BLAST algorithm was conducted. Here, we report genome-wide identification and characterization of 27 newly TaHSP20 candidate genes in wheat and 13 HvHSP20 in barley, describing structures, phylogenetic relationships, conserved protein motifs, and expression patterns. The structural analysis highlights that this gene family possesses a conserved ACD region at the C-terminal. Detailed pattern analysis of HSP20 revealed presence of P-G doublet and I/V/L-X-I/V/L motif that helps in oligomerization. Identification of conserved motif sequences of wheat and barley HSP20 strongly supported their identity as sHSP families. This study illustrates for the first time 3D model prediction of full-length wheat HSP20 (TaHSP20) protein and ACD region. Digital expression analysis was also carried out in order to reveal a widespread distribution of the sHSP family genes at various developmental stages of wheat and barley. In addition, five selected transcripts of both wheat and barley were validated for their expression profile under 35 °C and 42 °C heat stress conditions. Results indicate up-regulation of all the transcripts under heat stress condition except TaCBM38894 candidate, which showed down-regulation in wheat.