Modified expression of two receptor kinase genes in hexaploid oat (Avena sativa L.) on inoculation with crown rust

Abstract

An Lrk10 type of receptor kinase gene maps to three homoeologous linkage groups (KO4_12, KO5, and KO6) and also to a 4th (KO13) and a 5th unlinked locus. In linkage group KO4_12 it maps to the same location as the rust resistance genes Pg3, Pg9, Pc44, Pc46, Pc50, Pc68,Pc95 , and PcX. In this study, we used a short DNA fragment, encoding the extracellular domain of a receptor kinase gene as a probe to isolate receptor kinase gene-containing genomic DNA clones in hexaploid oat. One large genomic DNA clone was identified, which had two distinct receptor kinase genes, ALrk10 and Ork10, located head to head and sharing a putative bi-directional promoter. ALrk10 consists of three exons and two introns, Ork10 consists of 4 exons and 3 introns, and each encodes full length, functional receptor kinase proteins. Both genes are present in multiple copies in hexaploid oat genomes. They are expressed constitutively in leaf tissues of both resistant and susceptible plants. Their expression, however, was turned off or down in susceptible or compatible fungal-plant combinations, but remained unchanged in resistant or incompatible crown rust pathogen-plant combinations. The two coordinately expressed receptor kinase genes show a direct response to crown rust pathogen attack in oat plants. These results indicate that the receptor kinase genes, ALrk and Ork, are involved in the oat plants ability to respond to rust pathogen attack. Crown