AUTHOR=Xie Pengfei , Liu Jia , Lu Ruisen , Zhang Yanmei , Sun Xiaoqin TITLE=Molecular evolution of the Pi-d2 gene conferring resistance to rice blast in Oryza JOURNAL=Frontiers in Genetics VOLUME=13 YEAR=2022 URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2022.991900 DOI=10.3389/fgene.2022.991900 ISSN=1664-8021 ABSTRACT=

The exploitation of plant disease resistance (R) genes in breeding programs is an effective strategy for coping with pathogens. An understanding of R gene variation is the basis for this strategy. Rice blast disease, caused by the Magnaporthe oryzae fungus, is a destructive disease of rice. The rice blast resistance gene Pi-d2 represents a new class of plant R gene because of its novel extracellular domain. We investigated the nucleotide polymorphism, phylogenetic topology and evolution patterns of the Pi-d2 gene among 67 cultivated and wild rice relatives. The Pi-d2 gene originated early in the basal Poales and has remained as a single gene without expansion. The striking finding is that susceptible Pi-d2 alleles might be derived from a single nucleotide substitution of the resistant alleles after the split of Oryza subspecies. Functional pleiotropy and linkage effects are proposed for the evolution and retention of the disease-susceptible alleles in rice populations. One set of DNA primers was developed from the polymorphic position to detect the functional nucleotide polymorphism for disease resistance of the Pi-d2 gene based on conventional Polymerase Chain Reaction. The nucleotide diversity level varied between different domains of the Pi-d2 gene, which might be related to distinct functions of each domain in the disease defense response. Directional (or purifying) selection appears dominant in the molecular evolution of the Pi-d2 gene and has shaped its conserved variation pattern.