cDNA cloning and expression analysis of a putative alternative oxidase HsAOX1 from wild barley (Hordeum spontaneum)

A novel alternative oxidase (AOX1) gene, designated HsAOX1 (GenBank accession number JF440341) was cloned by RT-PCR from wild barley (Hordeum spontaneum). The full length of HsAOX1 is 1115 bp with an open reading frame of 987 bp, encoding a protein of 328 amino acids with molecular weight of 36.89 kDa and a theoretical isoelectric point of 6.81. As found in other plant AOX1 proteins, sequence alignment showed that HsAOX1 had conserved metal binding and hydrophobic ??-helix regions and had high homology to other AOX1 in plants. The expression analysis by semi-quantitative RT-PCR revealed that HsAOX1 was induced in response to cold stress, H₂O₂ treatment, SA, antimycin A and KCN. These results showed that HsAOX1 functions not only during inhibition of cytochrome electron transport but also during oxidative stresses, thus suggesting a role of HsAOX1 in preventing the generation of free radicals by the mitochondrial electron transport chain. The cloning and characterization of the HsAOX1 gene will be useful for further studies of biological roles of HsAOX1 in plants.