The maize inflorescences, the tassel and the ear, produce more grain than any other crop. The genetic processes that control tassel and ear development also underlie construction of inflorescence architecture across the grasses, including other grain and cereal crops that help feed the world. Thus, understanding the architecture of the maize ear is of especially broad relevance for agricultural research. When water availability is limited during the early growing season, early season drought stress disturbs or blocks maize ear development, which negatively impacts yield. Critical regulators of plant development and networks of gene expression that control distinct steps in generating maize ear architecture have been identified, but how they interact with drought stress is unknown. The project will use current knowledge as a foundation for understanding how two kinds of variation, in natural genetic factors and in the environment in the form of early season drought stress, modulate ear architecture.
Three scientific objectives will be pursued. First, existing high throughput genomics data will be integrated with more traditional breeding data as the basis of a web-accessible database. Serving as a repository for additional project data, and as a resource for queries by standard and specialized analysis tools, the database will thus provide rapid and complex data responses to address a spectrum of biologically relevant questions, including those in the project's second and third research objectives. Second, the nucleotide differences responsible for natural, quantitative genetic variation that controls the complex trait of inflorescence architecture will be elucidated. The project will use genomics tools and resources to identify and clone key genetic factors that have quantifiable effects on inflorescence architecture through their interactions with known genes. These quantitative genes will be integrated into emerging regulatory networks. Third, the mechanisms by which early season drought stress impacts the developmental processes that define the architecture of the maize ear will be identified. Here the project will couple spatial and temporal assessments of ear development to high throughput gene expression profiling.
These drought studies will spearhead interdisciplinary research at the interface of plant stress biology and development. Together the research will establish the molecular basis in maize of what plant breeders have historically called background effects, or the genetic landscape within which genes of major effect act, and illustrate how drought stress alters the timing and execution of endogenous mechanisms that regulate changes in inflorescence architecture.
Previous drought stress studies in maize have mostly focused on mid and late season growth periods, however early season drought stress, which affects the establishment of inflorescence development programs, also leads to substantial reductions in yields. Predicted changes in global climate and expanded cultivation of maize in developing countries will likely increase the impact of early season stress on yields. Understanding the genes and gene interactions that control maize inflorescence development, and how this transcriptional network responds to abiotic stress is necessary to provide the tools for sustaining maize yields. The project will provide insights to the important background effects that breeders seek to understand and address, and can work with. Thus, the research may ultimately be useful to plant breeders selecting for inflorescences that will be more productive in environments where drought stress is encountered. Seed stocks from the project will be available at the Maize Genetics Co-op Stock Center (http://maizecoop.cropsci.uiuc.edu/) and all project data will be made available from the project web site (http://www.maizeinflorescence.org), and distributed to permanent, public repositories such as MaizeGDB (http://www.maizegdb.org/). The project integrates highly controlled greenhouse conditions and agriculturally relevant field conditions with genomics resources to understand how environmental and developmental pathways converge. This work will cultivate broad and comprehensive training opportunities across diverse disciplines that encompass plant development, quantitative genetics, abiotic stress responses and bioinformatics. Educational training workshops will be organized to provide experiential learning opportunities both in the US and Mexico, in the lab and in the field. Postdoctoral scholars and graduate, undergraduate, and high school students will be mentored in the context of this multi-disciplinary research program.