US-Tunisia Planning Visit: The Genomics of Salinity Adaptation in the Medicago Truncatula-Sinorhizobium Symbiosis

University Of Southern California, Los Angeles CA

Investigators

Abstract

0751073 Nuzhdin This proposal is to support planning visits by the two PIs, Dr. Sergey Nuzhdin, Department of Molecular & Computational Biology, University of Southern California, Los Angeles and Dr. Sharon Strauss, Section of Evolution and Ecology, University of California at Davis, California to Tunisia, to establish research collaboration between them and Dr. Mohamed Elarabi Aouani, Center of Biotechnology, Technopole de Bordj Cedra (CBBC) in Hammam Lif, Tunisia. The PIs collaboration will also involve a number of French scientists working with Dr. Aouani. They plan to discuss the Genomics of Salinity Adaptation in the Medicago truncatula-Sinorhizobium symbiosis. They will participate in extensive discussions and tour the Tunisian lab, greenhouse facilities, and field sites. Dr. Aouani's team will contribute biological material, perform genetic characterization and greenhouse trials, and participate in field experiments during the course of the proposed project. Intellectual merit: Although Darwin emphasized the importance of ecological interactions for evolutionary diversification, we have only recently acquired the molecular tools that allow us to understand how adaptive variation evolves in response to environmental challenges and ecological interactions. The project will focus on an ecographically diverse Tunisian collection of Medicago truncatula (Mtr) and their nitrogen-fixing symbionts Sinorhizobium meliloti (Sm). The primary research goal is to identify networks of genes in the Mtr and Sm genomes that are involved in adaptation and coadaptation in response to high-salinity conditions. Genotypes from six focal populations, three from highly saline sites, will be tested under high vs. low salinity and in factorial combinations with rhizobial strains from high and low salinity sites, to document the roles of Mtr genotype, Sm genotype, and their interaction on performance under contrasting salinity regimes. Concurrent metabolome and transcriptome profiles will identify networks of genes associated with salinity tolerance and fitness tradeoffs between experimental treatments. Broader impacts: Increasing soil salinity is a major agricultural problem that will only become more urgent with continued irrigation. A long-term goal of this project is to facilitate the development of legume crops suited to saline environments, by identifying genetic pathways involved in salinity tolerance, and determining how these pathways influence the relationship of the host plant with its nitrogen-fixing symbiont. Because disparate regions of the world face similar environmental challenges, cross-cultural exchanges of knowledge and training are essential for science-based problem solving. The project will involve support for a U.S. post-doctoral scientist and a U.S. graduate student to participate in the visits.