Molecular Analysis of Fungal Pathogenesis
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The project will i) sampling grasses and wheat in Texas to identify Pyricularia isolates for analysis of the genetic diversity of the gene family to study the evolution of the gene family and to protect against the occurrence and spread of wheat blast in the US. ii) examine the expression and localization of a gene family found within Pyricularia species (also called Magnaporthe oryzae, Mo) using fluorescent protein fusions iii) assess their role in suppressing host programmed cell death, and iv) identification of candidate host target interacting proteins.Intellectual Merit: Understanding the roles of virulence factors is important for defining the plant host target and to developing strategies for plant protection. A novel gene family of 21 members found in Mo appears to play different roles in the interaction with the host. Previous work in Mo has focused on virulence factors that are unique genes, assessing the diversity and evolution of a large gene family will provide novel insight into evolution of pathogenicity and host adaptation. The gene family appears in Mo populations adapted to different hosts that have different combinations of alleles for the genes. This is particularly relevant to the evolution of pathogenesis to new hosts, such as wheat and maize. The model being tested is that the gene family has evolved to carry out a range of virulence functions against different host targets and that as grass species evolved or were domesticated, certain resistance traits were lost or fixed in the host population, and host targets diverged during speciation, requiring the Mo gene family to evolve during co-evolution with the host.Broader Impact: Wheat blast has become a significant threat to wheat production in South America. In April 2016, an outbreak occurred in Bangladesh and sequence analysis of mRNA of infected tissue suggest high similarity to isolates from South America suggesting the potential for migration. An alternate view is that Mo isolates on grasses are a source of wheat pathogens and that some wheat cultivars or changes in environment allow grass pathogens to move to wheat. To protect US wheat it is important to understand the genetic potential of US grass pathogens. Analysis of genotypes of grass isolates in Texas will provide a better understanding of the evolution of the Mo gene family that is the subject of this proposal and provide a baseline for distinguishing the potential sources of wheat blast that may occur in Texas in the future. If existing Texas isolates from grasses have the potential to infect wheat, it would provide important insight into strategies (cultivars, cultural practices) that may delay or prevent wheat blast occurrence in Texas and the US. If wheat blast has occurred by a host jump/shift, knowing the genotypes of native grass isolates will be important to identify the source of the pathogen and if the pathogen arrived by migration from South America, will help define how the migration occurred. Thus, the broader impact of the proposal is to help prevent global dispersal of wheat blast disease.