Isolation, characterization and expression of the maize Cat2 catalase gene.

The maize Cat2 gene was isolated by direct cloning and PCR. The clones were mapped and sequenced. The start site of transcription was determined by primer extension. Computer analysis of the 1.6 kb Cat2 promoter sequence has revealed an obvious TATA box, tow GC boxes, a putative GA response element, and several ACGT core sequences known to have diverse regulatory functions in plants. Several other protein binding motifs were also identified within 800 bp upstream from the transcriptional start site. Five introns were identified in the Cat2 coding region. All five Cat2 introns are located in exactly the same position as five of the six introns in Cat1. Two of the Cat2 introns are located in the same position as the two Cat3 introns. The identical positioning of these introns suggests an evolutionary link between all three maize catalase genes. The response of the CAt2 gene to plant growth regulators was examined. Results clearly showed that the response of CAt2 to several environmental factors are developmental stage-dependent. Thus, complex regulatory mechanisms appear to be involved in the regulation of Cat2 expression in maize.