Structure and chromosomal localization of the gene encoding barley seed peroxidase BP 2A.

A clone, lambda Prx6.1, coding for a barley seed peroxidase (BP; EC 1.11.1.7), was isolated from a genomic library using a cDNA coding for the barley seed peroxidase, BP 1, as a probe. The nucleotide sequence coded for a BP showing 73% amino acid (aa) sequence identity with BP 1 and less than 50% similarity with other sequenced plant peroxidases. The aa composition is 92% identical to that determined for BP 2 purified from mature barley grains, and therefore the gene product is named BP 2A. The alignment suggests that the coding region is interrupted by a 76-bp intron having the consensuses GT and AG, at the 5' and 3' ends, respectively. Alignment with BP 1 suggests that BP 2A has a leader peptide of 36 aa and the mature protein is 319 aa. Alanine and leucine account for 50% of the residues of the leader peptide. Of the codons used 90% have a C or G in the third position. The promoter shows a putative abscisic acid-response element, 5'-GTACGTGTC, 115 bp upstream from the start codon. The BP 2A-encoding gene was RFLP-mapped on barley chromosome 3, and we suggest for this peroxidase locus the name Prx6.