Deducing the Genomic Footprint and Functional Impact of Chickpea Domestication on Nitrogen Fixation

University Of California-Davis, Davis CA

Investigators

Abstract

PI: Douglas Cook (University of California - Davis) coPIs: Varma Penmetsa (University of California - Davis) and Eric von Wettberg (Florida International University) Collaborator: Abdullah Kahraman (Harran University, Turkey) Legume species are key components of both natural and agricultural ecosystems. Their importance derives in large part from their capacity for symbiotic nitrogen fixation with soil bacteria, enabling them to return vital nitrogen to the soil environment and to create seed and forage of high protein content. Two decades of molecular and genomic studies in model systems have revealed the presence of exquisite genetic pathways that initiate symbiosis, but despite these advances essentially little is known about genes that regulate symbiotic performance in the natural environment. Research under this project strives to understand the evolution of symbiotic performance in the wild progenitors of legume crops and the ways in which human selection has reshaped this potential during domestication. The research combines ecology and population genomics with classical molecular genetics and reverse genetic assays to deduce the functional consequences of standing variation in wild populations of Cicer reticulatum and its domesticated counterpart Cicer arietinum (chickpea). Project outcomes will expand our knowledge of symbiotic nitrogen fixation in novel ways, and will contribute to an emerging paradigm in plant biology where the intersection of ecology, genomics and molecular biology empowers the study of gene function in natural and human-built environments. Importantly, the outcomes should have relevance to both basic science and to agriculture. Legumes provide an estimated 30% of humankind's nutritional nitrogen, while in agricultural systems crop rotations with legume species provide an important means to maintain soil fertility. Despite legumes' comparative advantage of N-fixation, nitrogen fertilizers are often added during legume cultivation and legumes are often grown under high residual nitrogen following cereal crops. These practices relax selection on nitrogen fixation traits and contribute in a substantial way to environmental degradation through nitrogen runoff. Improved understanding of the processes that regulate N-fixation in natural and agricultural environments will ultimately enable rationale strategies to mitigate these situations. Of more immediate impact, researchers on this project are mentoring under-represented minorities as young biologists by participating in established high school science programs at UC Davis and the Fairchild Botanical Garden. The project will provide training for undergraduate students in laboratory science, while mentoring their academic and professional development. Data and biological resources generated under this project will be available through public repositories, including the National Center for Biotechnology Information (NCBI) and through the Germplasm Resource Information Network (GRIN) of the USDA Agricultural Research Service. Information will also be provided through a project-specific web site.