ISOLATION AND CHARACTERIZATION OF A GENOMIC SEQUENCE ENCODING THE MAIZE CAT3 CATALASE GENE

A maize genomic DNA library (Zea mays L. W64A) was constructed using the lambda GEM-11 vector. A gene-specific Cat3 cDNA probe was used to screen the library by plaque hybridization. Two independent clones, lambda24C and lambda27C, which hybridized to the Cat3 cDNA probe, were isolated. Restriction maps were created for the two clones (lambda24C and lambda27C) encoding the maize Cat3 catalase gene. A Sal I restriction fragment from each clone was subcloned into pBluescript KS+. Subsequent subcloning steps were performed to obtain plasmids suitable for sequencing. Both strands of the lambda24C clone were sequenced. Computer analysis of the putative Cat3 promoter region has not revealed any known transcription factor binding motifs. Analysis of the deduced C-terminal amino acids encoded by Cat3 shows that CAT-3 lacks the SRL peroxisomal targeting sequence contained in the CAT-1 and CAT-2 isozymes. The DNA sequence and physical structure of the Cat3 gene presented here will be used in characterizing cis- and trans-acting factors affecting Cat3 gene expression.