Thesis subject

Genotype - Environment interactions: Identification of genes underlying phenotypic plasticity in the nematode Caenorhabditis elegans

The phenotypes of organisms result from complex networks of interactions between different genes, and between these genes and the environment. The extent to which a genotype can change its phenotype in a range of environ­ments (phenotypic plasticity) is essential for the survival of organisms and ­is a trait in itself, subjected to evolutionary forces like all other genetically determi­ned characters. Plastici­ty has been shown in various phenotypic traits ranging from morpholo­gy, growth, and repro­duction to life expectancy and expression of diseases. However, the under­lying genetic mechanism of this phenomenon is unclear.

The objective of this proposal is to identify genes in the nematode Caenorhabdi­tis elegans underlying plasticity in life-cycle traits. Research will focus on plasticity to temperature in maturation time, growth and life expectancy. Since i) C. elegans is amenable for genetic studies and inbred strains can easily be crossed and differ in plasticity, ii) the latest developments in DNA-marker technology allow the generation of numerous genetic markers, and iii) C. elegans will be the first animal whose genome will be completely sequenced in 1998, C. elegans provi­des a perfect model for this project. The following tasks will be carried out: 1) crossing of wild strains yielding approx. 1000 recombinant inbred lines, 2) construction of a highly saturated linkage map, 3) measuring plasticity in life-cycle traits in recombinant inbred lines, 4) mapping QTL’s associated with plasticity, 5) identification of genes using a candidate gene approach. To study the “plasticity genes” in more detail, “knock-out” mutants will be generated by chemical deletion mutagenesis and/or transposon tagging. The outcome of this project will be a first step in post-sequence genetics of C. elegans and may serve as an example for the functional analysis of other eukaryotic genomes, including human. Furthermore it will elucidate the biological significance and functi­on of genotype-environment interactions involving polygenic traits. An important spin-off will be the availability of a high density linkage map of C. elegans for the scientific community.