Differential Expression of Copper-Zinc Superoxide Dismutase Gene of Polygonum sibiricum Leaves, Stems and Underground Stems, Subjected to High-Salt Stress

In aerobic organisms, protection against oxidative damage involves the combined action of highly specialized antioxidant enzymes, such as copper-zinc superoxide dismutase. In this work, a cDNA clone which encodes a copper-zinc superoxide dismutase gene, named PS-CuZnSOD, has been identified from P. sibiricum Laxm. by the rapid amplification of cDNA ends method (RACE). Analysis of the nucleotide sequence reveals that the PS-CuZnSOD gene cDNA clone consists of 669 bp, containing 87 bp in the 5' untranslated region; 459 bp in the open reading frame (ORF) encoding 152 amino acids; and 123 bp in 3' untranslated region. The gene accession nucleotide sequence number in GenBank is GQ472846. Sequence analysis indicates that the protein, like most plant superoxide dismutases (SOD), includes two conserved ecCuZnSOD signatures that are from the amino acids 43 to 51, and from the amino acids 137 to 148, and it has a signal peptide extension in the front of the N-terminus (1-16 aa). Expression analysis by real-time quantitative PCR reveals that the PS-CuZnSOD gene is expressed in leaves, stems and underground stems. PS-CuZnSOD gene expression can be induced by 3% NaHCO3. The different mRNA levels' expression of PS-CuZnSOD show the gene's different expression modes in leaves, stems and underground stems under the salinity-alkalinity stress.