Molecular Characterization of Novel Rp1 Genes

Kansas State University, Manhattan KS

Investigators

Abstract

Rp1 is a complex disease resistance locus of maize that has been extensively characterized genetically. The Rp1 haplotypes in different maize lines are composed of variable numbers of members of an NBS-LRR gene family. This class of gene is thought to function by recognizing ligands from pathogens and then activating defense responses. Recent genetic studies have indicated the different rp1 family members mispair and recombine frequently in meiosis, and the crossover events are typically intragenic and occur throughout the genes. A large collection of novel rp1 haplotypes has now been generated which confer a variety of novel phenotypes. These phenotypes include new race specificities, presumably by the ability to recognize novel pathogen ligands. They also include nonspecific resistance to multiple rust species, lesion mimic and necrotic phenotypes. Progress has been made in characterizing these variant haplotypes and recombinant genes have been isolated from haplotypes conferring lesion mimic phenotypes or modified resistance. Recombinant genes will now be expressed in transgenic plants to verify they confer the novel phenotypes. Recombinant genes from haplotypes with novel race specificities and necrotic phenotypes will be isolated and compared to their parental genes to examine the mechanism by which they arose. These experiments will elucidate the mechanisms in which complex resistance loci like rp1 evolve and provide a framework for how these genes might be manipulated to engineer effective and durable disease resistance.