Genotype-phenotype maps and non-standard heredity in C. elegans
Institut de Biologie de l'École Normale Supérieure, Paris
A key question is the extent to which the process of phenotype construction biases and constrains phenotypic evolution. In other words, do directions of phenotypic space with high sensitivity to random mutation correspond to directions of fast evolution? The development of the vulva in the nematodeCaenorhabditis elegans provides a model system where the fates and variational properties of each of six precursor cells can be compared quantitatively. Caenorhabditis and Oscheius are twoi genera with contrasted patterns of evolutionary variation in these cell fates. We examined their sensitivity to random mutation and their evolutionary variation within and among species of each genus. Overall, our results indicate that the sensitivity to molecular dose variation of a developmental system may produce evolutionary trends at the phenotypic level.
Besides this standard “genetic” variation, the recent molecular insights into non-standard heredity raise evolutionary questions. In C. elegans, non-standard genetic heredity includes the transmission of small RNAs affecting histone modifications and gene expression. Our work shows that C. elegans harbors natural genetic variation in such non-genetic inheritance phenomena.