Cloning and expression analysis of HSP70 gene from mangrove plant Kandelia obovata under cold stress

Heat shock protein 70 (HSP70), the primary member of the HSPs that play various stress-protective roles in plants. In this study, a hsp70 gene of Kandelia obovata (KoHsp70) was cloned by rapid amplification of cDNA ends (RACE). The full-length of KoHsp70 was 2255 bp, consisting of a 5′-terminal untranslated region (UTR) of 118 bp, a 3′-terminal UTR of 178 bp, and an open reading frame (ORF) of 1959 bp. The ORF (KoHSP70) was predicted to encode a polypeptide of 652 amino acids with a theoretical molecular weight (MW) of 71.40 kDa and a pI of 5.16. The amino acid sequence analysis revealed that the KoHSP70 contained three conserved regions of HSP70 family, a bipartite nuclear localization signal sequences (NLS), an ATP/GTP-binding site motif and a cytoplasmic characteristic motif (EEVD). Homology analysis indicated that KoHSP70 shared 96.0 % identity with the known HSP70 (Gossypium hirsutum). Bioinformatics analysis indicated that the KoHSP70 was hydrophilic and had no signal peptide or transmembrane region. The mRNA expression of KoHsp70 kept relatively stable at first and then increased significantly after 48 h cold stress, and reached the highest level at 168 h after cold treatment. The results indicated that the KoHsp70 was a stress-inducible gene that might play a role in cold stress-protective response and in coping with environmental and biological stresses for K. obovata. This study provided a basis to further study the mechanism of anti-adverseness and expression characteristics under stress conditions of K. obovata.