Cloning and expression of a small heat and salt tolerant protein (Hsp22) from Chaetomium globosum.

The present study reports molecular characterization of small heat shock protein gene in Indian isolates of Chaetomium globosum, C. perlucidum, C. reflexum, C. cochlioides and C. cupreum. Six isolates of C. globosum and other species showed a band of 630bp using specific primers. Amplified cDNA product of C. globosum (Cg 1) cloned and sequenced showed 603bp open reading frame encoding 200 amino-acids. The protein sequence had a molecular mass of 22 kDa and was therefore, named Hsp22. BlastX analysis revealed that the gene codes for a protein homologous to previously characterized Hsp22.4 gene from C. globosum (AAR36902.1, XP 001229241.1) and shared 95% identity in amino acid sequence. It also showed varying degree of similarities with small Hsp protein from Neurospora spp. (60%), Myceliophthora sp. (59%), Glomerella sp. (50%), Hypocrea sp. (52%), and Fusarium spp. (51%). This gene was further cloned into pET28a (+) and transformed E. coli BL21 cells were induced by IPTG, and the expressed protein of 30 kDa was analyzed by SDS-PAGE. The IPTG induced transformants displayed significantly greater resistance to NaCl and Na2CO3 stresses.