Structure and expression of the barley stem rust resistance gene Rpg1 messenger RNA

Abstract

The barley stem rust resistance gene Rpg1 confers resistance to many pathotypes of the stem rust fungus Puccinia graminis f. sp. tritici. Rpg1 was recently cloned by a map-based approach from the barley cultivar Morex. Haplotype sequencing and transformation of a susceptible barley cultivar were employed to prove its identity. As a first step in understanding the molecular mechanism of action of Rpg1, we characterized the structure and transcription of the Rpg1 messenger RNA. Several alternative splice forms were identified, some of which could be translated into a predicted full-length protein product. The expression of the gene occurred in all plant organs and developmental stages analyzed. However, leaf epidermis exhibited ca. 30-fold higher Rpg1 expression than the whole leaf. Expression of Rpg1 was not induced by infection of barley cultivar Morex seedlings with the incompatible P. graminis f. sp. tritici pathotype MCC, while some defense-related genes, such as barley β-1,3-glucanases and PR1a, were strongly induced.