Chromosomal locations of six barley genes encoding enzymes of chlorophyll and heme biosynthesis and the sequence of the ferrochelatase gene identify two regulatory genes

The chromosomal location of six barley genes was determined by Southern blot experiments using wheat strains which contained the short or long arm from one of the seven barley chromosomes. The genes analysed encode enzymes that are required for chlorophyll and heme synthesis. Glutamyl-tRNAGlu synthetase, glutamate 1-semialdehyde 2,1-aminotransferase and glutamyl-tRNAGlu reductase are common to both pathways and catalyse the initial reactions from glutamate to 5-aminolevulinic acid. Magnesium chelatase and ferrochelatase are at the branch between chlorophyll and heme synthesis and insert magnesium and ferrous, respectively, into protoporphyrin IX. The chromosomal locations of the barley structural genes for the following enzymes were: glutamyl-tRNAGlu synthetase — short arm of chromosome 6 (6H); glutamate 1-semialdehyde 2,1-aminotransferase — β arm of chromosome 1 (7H); ferrochelatase — long arm of chromosome 7 (5H); magnesium chelatase subunit Xantha-F — short arm of chromosome 2 (2H); magnesium chelatase subunit Xantha-H — α arm of chromosome 1 (7H). Two glutamyl-tRNAGlu reductase genes were found in the barley genome and one was localised on the short arm of chromosome 5 (1H). It is suggested that the other reductase gene is located on the long arm of chromosome 5 (1H). The barley ferrochelatase gene consists of nine exons and was isolated and sequenced from wild type and two mutant barley, tigrina-d12 and tigrina-o34, and is located on chromosome 7 (5H). In all three cases, an identical sequence was obtained, excluding the possibility that the deregulated synthesis of 5-aminolevulinic acid in the two tigrina mutants results from mutations in the ferrochelatase gene.