Functional Genomics of Maize Gametophytes

Carnegie Institution Of Washington, Washington DC

Investigators

Abstract

PI: Matthew Evans (Carnegie Institution of Washington) CoPIs: Donald Auger (South Dakota State University; subawardee), John Fowler and Scott Givan (Oregon State University; subawardees), Erik Vollbrecht (Iowa State University; subawardee) Collaborator: Kelly Beck, Gabriel Garcia (Stanford University; subawardees) An understanding of the genetic basis of gametophyte function will have important implications for agriculture, as gametophytes are central to plant reproduction. The female and male gametophytes make up the haploid phase of the angiosperm life cycle, which immediately succeeds meiosis and precedes formation of the seed (embryo and endosperm). Although gametophytes are small and undergo few cell divisions, they are crucial for reproduction, as they produce gametes, control the fertilization process, and influence development of the seed. However, because mutations that are deleterious to these haploid tissues are difficult to recover and maintain, relatively little is known about the genetic and cellular mechanisms underlying gametophyte function and development, especially in crop plants. This project seeks to overcome this limitation using genetic tools unique to the model crop Zea mays (maize) to accomplish a genomic-scale investigation of gametophytically-required genes. Trisomic stocks that transmit duplicate chromosomal regions through the gametophyte will be used to screen for Activator transposon-tagged gametophyte-lethal mutants. The phenotype of these mutants will be characterized in male and female gametophytes, and the corresponding DNA sequences of the mutated genes identified. Verification of the identity of a select group of candidate genes will be accomplished using multiple alleles and RNA expression analyses. Complementary aims in expression profiling of gametophytes and in bioinformatics - to identify orthologous genes in other plant models and integrate the data generated by the project - will allow an assessment of the genetic basis of gametophyte function. Finally, the ability to predict gametophytic functions across species boundaries will be tested using RNA interference to target select genes in the dicot model Arabidopsis thaliana. Broader Impacts: This project is relevant to many agricultural objectives seeking to influence plant reproduction - for example, controlling pollen fertility for hybrid seed production, limiting pollen-mediated transgene flow, and inducing apomixis. Because the tools and stocks created, and sequences generated, will be freely available to the scientific community, the project will enable other researchers to better investigate gametophytes through creation of a gametophyte-specific sequence-indexed mutant collection. All stocks created by the project will be deposited in the Maize Coop Stock Center (maizecoop.cropsci.uiuc.edu). All Ac transposon flanking sequences will be searchable by BLAST, both at PlantGDB (www.plantgdb.org), and at the project''s database: ZGamDB (maizegametophyte.org). Phenotypic and expression data will also be accessible at ZGamDb. For long-term storage and broad community access, phenotypic and genetic data will be incorporated into MaizeGDB (www.maizegdb.org), and expression data will be deposited at the Gene Expression Omnibus (www.ncbi.nlm.nih.gov/geo) and the Plant Expression Database (www.plexdb.org). The project will help train 10 undergraduates to serve as science mentors for K-12 students, through exposing them to plant science research. In partnership with Stanford University''s Haas Center for Public Service, these undergraduate mentors will be placed in communities with large populations from under-represented groups, and help develop science experiences for K-12 students. In addition, the project will train two postdoctoral researchers and a graduate student in genomic-scale approaches to plant biology, and will introduce undergraduates and high school students to genomic science.