Jelisaveta Djordjevic, Zoé Dumas, Marc Robinson-Rechavi, Tanja Schwander, Darren James ParkerPlease use the format "First name initials family name" as in "Marie S. Curie, Niels H. D. Bohr, Albert Einstein, John R. R. Tolkien, Donna T. Strickland"
<p style="text-align: justify;">Sexually dimorphic phenotypes are thought to arise primarily from sex-biased gene expression during development. Major changes in developmental strategies, such as the shift from hemimetabolous to holometabolous development, are therefore expected to have profound consequences for the dynamics of sex-biased gene expression. However, no studies have previously examined sex-biased gene expression during development in hemimetabolous insects, precluding comparisons between developmental strategies. Here we characterized sex-biased gene expression at three developmental stages in a hemimetabolous stick insect (<em>Timema californicum</em>): hatchlings, juveniles, and adults. As expected, the proportion of sex-biased genes gradually increased during development, mirroring the gradual increase of phenotypic sexual dimorphism. Sex-biased genes identified at early developmental stages were generally consistently male- or femalebiased at later stages, suggesting their importance in sexual differentiation. Additionally, we compared the dynamics of sex-biased gene expression during development in <em>T. californicum</em> to those of the holometabolous fly <em>Drosophila melanogaster</em> by reanalyzing publicly available RNA-seq data from third instar larval, pupal and adult stages. In D. melanogaster, 84% of genes were sex-biased at the adult stage (compared to only 20% in <em>T. californicum</em>), and sex-biased gene expression increased abruptly at the adult stage when morphological sexual dimorphism is manifested. Our findings are consistent with the prediction that the dynamics of sex-biased gene expression during development differ extensively between holometabolous and hemimetabolous insect species.</p>
Timema, sex-biased gene expression, development, Drosophila
Evo-Devo, Evolutionary Dynamics, Evolutionary Ecology, Expression Studies, Genotype-Phenotype, Molecular Evolution, Reproduction and Sex, Sexual Selection