Structure of Peroxidase Isozyme Genes in Brassica and Their Expression.

We have isolated 5 genomic DNAs (prxC1a. prxC1b. prxC1c. prxC2 and prxC3 @#@) coding for horseradish peroxidase (HRP). All 5 genes consisted of 4 exons and 3 introns, and the positions of introns in the coding regions were same in all genes. Putative promoter sequences and polyadenylation signals were also found. Two peroxidase genes (prxCa and prxEa) of Arabidopsis thaliana which belongs to the same family of horseradish, Brassica.were also cloned. The structures and sequences of the coding regions of prxCa. and prxEa were very similar to prxC1b and prxC3, respectively. Transcripts of all HRP genes were abundant in horseradish cultured cells, but organspecific expression was observed in horseradish plant. prxC1 was expressed in root and stem, C2 in stem, and C3 in root. 5'-Noncoding regions of HRP isozyme genes were joined to β-glucuronidase (GUS) reporter gene and introduced into tobacco protoplast by electroporation. Promoter activity was detected in every construct, especially prxC2 gene showed several times higher activity of CaMV35S promoter. The promoter-GUS fused genes were transferred to tobacco leaf disk using binary vector system with Aqrobacteriumtumefaciens. Strong GUS expression was observed in root of transgenic tobacco, but not in leaf. When callus was induced from leaf, GUS activity enhanced 15 -50 time of that in leaf in all promoter regions as observed in horseradish callus. [ABSTRACT FROM AUTHOR]