Identifying candidate genes affecting developmental time in Drosophila melanogaster: pervasive pleiotropy and gene-by-environment interaction.

MENSCH JULIÁN; LAVAGNINO NICOLÁS; CARREIRA VALERIA; HASSON ESTEBAN; FANARA JUAN JOSÉ

Buenos Aires

Congreso; 4º LatinAmerican Meeting of Developmental Biology; 2008

Sociedad Latinoamericana de Biología del Desarrollo

Background: Understanding the genetic architecture of ecologically relevant adaptive traitsrequires the contribution of developmental and evolutionary biology. The time to reach the age ofreproduction is a complex life history trait commonly known as developmental time. In particular,in holometabolous insects that occupy ephemeral habitats, like fruit flies, the impact ofdevelopmental time on fitness is further exaggerated. The present work is one of the firstsystematic studies of the genetic basis of developmental time, in which we also evaluate the impact of environmental variation on the expression of the trait.Results: We analyzed 179 co-isogenic single P[GT1]-element insertion lines of Drosophilamelanogaster to identify novel genes affecting developmental time in flies reared at 25°C. Sixtypercent of the lines showed a heterochronic phenotype, suggesting that a large number of genesaffect this trait. Mutant lines for the genes Merlin and Karl showed the most extreme phenotypesexhibiting a developmental time reduction and increase, respectively, of over 2 days and 4 daysrelative to the control (a co-isogenic P-element insertion free line). In addition, a subset of 42 lines selected at random from the initial set of 179 lines was screened at 17°C. Interestingly, the geneby-environment interaction accounted for 52% of total phenotypic variance. Plastic reaction norms were found for a large number of developmental time candidate genes.Conclusion: We identified components of several integrated time-dependent pathways affectingegg-to-adult developmental time in Drosophila. At the same time, we also show that manyheterochronic phenotypes may arise from changes in genes involved in several developmentalmechanisms that do not explicitly control the timing of specific events. We also demonstrate thatmany developmental time genes have pleiotropic effects on several adult traits and that the actionof most of them is sensitive to temperature during development. Taken together, our results stressthe need to take into account the effect of environmental variation and the dynamics of geneinteractions on the genetic architecture of this complex life-history trait.