Cloning and expression of a new cytoplasmic small heat shock protein gene from Pinellia ternata

A new cytoplasmic small heat shock protein gene was cloned from Pinellia ternata (Thunb.) Breit and designated PtHSP18.2 (GenBank number: KF693218). The PtHSP18.2 gene has an open reading frame of 711 bp that encodes 159 amino acids, and a molecular mass of 18.20 kDa. The phylogenetic tree indicated high homology of the PtHSP18.2 protein with that of cytosolic class I small heat shock proteins (CI sHSPs) from other plant species. PtHSP18.2 is expressed in root, leaf, and stem tissues. The expression of PtHSP18.2 was increased under heat and cold stress but was not induced by drought stress. When overexpressed in E. coli, PtHSP18.2 was correlated with the preservation of viability under heat stress. The CI sHSP family is the largest sHSP subfamily, and several different members of this subfamily are present in P. ternata. Two-dimensional electrophoresis (2-DE) western blot analysis with an anti-AtHSP17.7 (a member of CI sHSPs) antibody revealed five 18 kDa heat shock-induced P. ternata proteins. In combination, our findings suggest that PtHSP18.2 is potentially significant in the response to thermal stress.