Global Constraints within the Developmental Program of the Drosophila Wing

Organismal phenotypes emerge from a complex set of genotypic interactions. While technological advances in sequencing provide a quantitative description of an organism’s genotype, characterization of an organism’s physical phenotype lags far behind. Here, we relate genotype to the complex and multi-dimensional phenotype of an anatomical structure using the Drosophila wing as a model system. We develop a mathematical approach that enables a robust description of biologically salient phenotypic variation. Analysing natural phenotypic variation, and variation generated by weak perturbations in genetic and environmental conditions during development, we observe a highly constrained set of wing phenotypes. In a striking example of dimensionality reduction, the nature of varieties produced by the Drosophila developmental program is constrained to a single integrated mode of variation in the wing. Our strategy demonstrates the emergent simplicity manifest in the genotype-to-phenotype map in the Drosophila wing and may represent a general approach for interrogating a variety of genotype-phenotype relationships.

Our first generation of results suggested the presence of a soft mode in the dynamical system that is the development of the wing close to final form. The soft mode leads to “developmental epistasis” wherein the peculiarities of genetic mutations and environmental variations are funneled into a single, spatially-extended, mode of variation. 

Our second generation of resutls suggests, that avolutionary level data are in teh aggreement with the evelopental picture.