Basic characterization of two barley hemA promoter regions reveals stem-loop structures and suggests a regulatory role in Poaceae tetrapyrrole biosynthesis

5-Aminolevulinic acid (ALA) is a common biosynthetic intermediate of both chlorophyll and heme. Glutamyl tRNA(Glu) reductase, encoded by the hemA gene, is the initial enzyme of ALA biosynthesis. The presence of several hemA genes provides a possible explanation to the ability of plants to meet the different requirement of chlorophyll and heme using a common biosynthetic pathway. In this work, two barley (Hordeum vulgare L.) hemA genes were cloned from chromosomal DNA. The hemA1 and hemA2 genes are located at the long and short arm, respectively, of barley chromosome 5 (1H). Although having 98 % identical coding sequences the promoter regions of hemA1 and hemA2 are very different, which could explain their different expression patterns. The first 170 nucleotides of the coding region of both genes contain several inverted repeat regions capable of forming stern-loop structures, which could be involved in the regulation of tetrapyrrole biosynthesis in species belonging to the Poaceae family. (C) 2001 Editions scientifiques et medicales Elsevier SAS.