Isolation and expression analysis of chloroplastic copper/zinc superoxide dismutase gene in barley

Superoxide dismutase is considered to be a crucial component in biological defense against oxidative stress. A full-length cDNA clone encoding a putative chloroplastic Cu/Zn-SOD from barley seedlings (Hordeum vulgar cv. Rum) was isolated by RT-PCR from cDNA synthesized from leaf mRNA. HvSOD cDNA is 760 bp in length, which translates an ORF of 201 amino acids that correspond to a protein of predicted molecular mass of 20.21 kDa and a pI of 5.31.The deduced amino acid sequence of HvSOD showed higher identity (72–95%) with the sequences of the chloroplastic Cu/Zn-SODs than those of the cytosol from other species. Moreover the cloned sequence showed all the typical structural motifs of plant chloroplastic SODs with a 47 bp plastid targeting peptide. These results suggested that the HvSOD is chloroplastic. Reverse transcription-PCR analysis was used here to investigate the expression patterns of HvSOD in response to abiotic stresses. The HvSOD gene was induced in leaf tissues in response to drought, cold stress and exposure to stress related chemicals, indicating that it is involved in the antioxidative process under various environmental stresses.

Research Highlights
► Superoxide dismutase plays a central role in protecting plants against oxidative stress.
► Chloroplastic Cu/Zn-SOD from barley seedlings was isolated by RT-PCR.
► HvSOD showed higher identity with the sequences of the chloroplastic Cu/Zn-SODs.
► HvSOD was induced in response to drought, cold stress and exposure to stress related chemicals.