Abstract:

【Objective】 Sulfite oxidase (SO) plays an important role in sulfur metabolism and sulfur dioxide detoxification in higher plants. To date, most reports on plant SO have focused on Arabidopsis, but little is known about SO in cereal crops such as maize. The objectives of this study are to clone the sulfite oxidase gene and to understand its expression in maize under SO2 stress. This study will provide a basis for genetic improvements in environmental pollutant tolerance (SO2 and acid rain) in maize. 【Method】 The SO gene from maize was cloned by RT-PCR and RACE, and its expression was analyzed under SO2 stress using semi-quantitative RT-PCR method. 【Result】 The full-length sulfite oxidase (SO) cDNA, named ZmSO (GenBank accession number FJ436404), was cloned from an elite inbred Q9. The cDNA contains a 1 194-bp open reading frame (ORF) and encodes 397 amino acids. Sequence alignment and structure prediction showed that the deduced amino acid sequence of ZmSO shared 72%, 74%, and 89% similarities with homologs from other plants such as Arabidopsis thaliana, Lycopersicon esculentum and Oryza sativa, respectively. In addition, similar to other plant SO homologs, ZmSO also contained three conserved functional domains such as one Moco-binding domain, one dimerization domain and one peroxisome targeting signal. Semi-quantitative RT-PCR analysis demonstrated that ZmSO expression was up-regulated significantly in resistant inbred Q9 after treatment with higher concentration of SO2, but not in sensitive inbred Chang7-2. 【Conclusion】 The isolated ZmSO from maize is orthologous to other plant species, and its expression is up-regulated by SO2 stress in the highly resistant line, indicating that the SO from maize may be involved in resistance responses of resistant maize plants to SO2 stress.

Key words: maize, sulfite oxidase, stress, expression