Marta Coronado Zamora (Universitat Autònoma de Barcelona)
in: 'Frontiers in Ecology and Evolution': "Mapping selection within Drosophila melanogaster embryo’s anatomy"
by Marta Coronado Zamora (Universitat Autònoma de Barcelona)
The measure of adaptation is a main pursuit of evolutionary biology. Here we present a new approach that integrates data from genomic variation, spatial gene expression patterns and development to map adaptation over the entire embryo’s anatomy of Drosophila melanogaster. The resulting adaptation map is based on spatial information of gene expression of 5,969 genes (from text-based annotations of in situ hybridization data directly from the BDGP database) and nucleotide polymorphism and divergence data for these genes (from the DGRP project). The proportion of non-synonymous substitutions that are adaptive, neutral or slightly deleterious are estimated for the set of genes expressed in each embryonic anatomical structure using the DFE-alpha method, a robust derivative of the McDonald and Kreitman test. We also explore whether different anatomical structures differ in the phylogenetic age, codon usage or expression bias of the genes they express and whether the genes that are more widely expressed in anatomical structures show higher amount of adaptive substitutions. We found that: (i) most of the digestive system and ectoderm-derived structures are under constraint, (ii) the germ line and some specific mesoderm-derived structures show high rates of adaptive substitution and (iii) the genes that are expressed in a small number of anatomical structures show higher expression bias, lower phylogenetic ages and less constraint. This new approach, when applied to the exponential growth of both population genomic and omics data, will shed new insights on the ways that natural selection operates in the whole organisms.