ARS | Publication request: MOLECULAR CLONING, CHARACTERIZATION AND EXPRESSION ANALYSIS OF TWO CATALASEISOZYMAL GENES IN BARLEY

Submitted to: Plant Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 23, 1995
Publication Date: N/A

Interpretive Summary: When plants are attacked by diseases, or when they undergo stresses (chilling, ultraviolet light, high light and heat), they produce high amounts of harmful chemicals known as oxygen free radicals. The enzyme catalase, which is normally present in various plant parts, inhibits free radical formation. We have cloned and characterized the genes in barley which produce two different types of catalase. We have determined where and when the enzymes are produced in seedlings. We have also shown that other cereal catalases can be classified as belonging to one of these types. This research may lead to our ability to alter the amount or type of catalase in plants enabling them to tolerate stress and avoid the effects of disease. This will enable the production of better quality cereal products.

Technical Abstract: Clones for two distinct barley catalase genes, Cat1 and Cat2, were found in a seedling cDNA library. Both were sequenced, and their deduced amino acid sequences have high homology with maize and rice catalase genes. Barley, maize or rice isozymes were divided into two groups, with one homologous to the mitochondria-associated CAT-3 or maize and the other homologous to the maize peroxisomal/glyoxysomal CAT-1. Both barley CATs contained possible peroxisomal targeting signals, but neither had favorable mitochondrial targeting sequences. Cat1 mRNA occurred in whole endosperms, in aleurones and in developing seeds, but Cat2 was virtually absent. Both mRNAs displayed different developmental expression patterns in scutella. Cat2 mRNA predominated in etiolated seedlings shoots and leaf blades. Genomic DNA contained two genes for Cat1 and one for Cat2. Cat2 was mapped to the long arm of chromosome 4, 2.9 cM in telomeric orientation from the mlo locus conferring resistance to the powdery mildew fungus (Erysiphe graminis f. sp. hordei).