NSF-REU
RESEARCH EXPERIENCES FOR UNDERGRADUATES FROM RURAL AND TRIBAL COLLEGES 

InvestigatorBrian Darby, Ph.D.

Location:  Department of Biology, University of North Dakota

Project Title:  Genetic basis of stress tolerance in grassland soil nematodes

Description:  Nematodes that feed on bacteria perform a number of important functions in soil ecosystems as they disperse microbes throughout the soil, regulate the microbial communities on which they feed, and regulate the rate and chemistry in which soil organic matter is transformed into inorganic and dissolved organic nitrogen.  Many species are exposed to rapid desiccation, freezing or heat stress.  The main objective of this research is to understand what genes are differentially regulated by soil nematodes in response to abiotic stresses, and how this differs between species.  The production of membrane protecting proteins and metabolites is a recurring theme in the cellular response of nematodes to desiccation, freezing, and thermal stress.  From a histological perspective, this is not surprising, as membrane rupture is one of the primary biophysical threats from these abiotic stressors.  Non-reducing disaccharides, such as trehalose, are used by some nematodes to maintain membrane integrity during anhydrobiosis or cryobiosis.  These compounds associate with membranes to prevent shearing during desiccation or ice nucleation.  Trehalose is synthesized by Trehalose-6-Phosphate Synthase (T6P) and catabolized by trehalase.
Caenorhabditis elegans is particularly suitable for studying organism-environment interactions in a genetic context because they can be cultured easily in laboratory environments, have short generation times of days to weeks, and benefit from the genomic tools and sequence data obtained from being the first fully sequenced multi-celled organism.  Genetic mutants from an EMS screen that are deficient for both the T6P (tps-1,2) and trehalase (tre-1,2,3,4,5) genes are available from the Caenorhabditis Genetics Center (Minneapolis, MN) and can be used to test the role of T6P and trehalase on C. elegans' abiotic stress tolerance by subjecting these mutants to standardized desiccation, freezing, and heat stress assays.