Genetic variation for heat thermotolerance in eggs as compared to other stages of the life cycle in Drosophila melanogaster

NORRY FM; STAZIONE LEONEL; BORDA MIGUEL ANGEL; SAMBUCETTI PABLO; GOMEZ FEDERICO

Simposio; IEPEP 8th International Symposium on the Environmental Physiology of Ectotherms and Plants; 2019

Evolutionary changes for adaptation to high-temperature environments require genetic variation for thermotolerance in all stages of the life cycle. In the model insect Drosophila melanogaster, thermotolerance phenotypes have been mapped for quantitative trait loci (QTL) in previous studies in both larvae and adults but not yet in eggs. Here we QTL-mapped hatch ability of eggs with and without exposure to heat stress. We used recombinant inbred lines (RIL) and composite interval mapping. RIL were previously obtained from a crossing between a Danish line (D48) and an Australian line (SH2) selected for low (D48) and high (SH2) resistance for heat stress in adult flies. Two main results were obtained. First, eggs were found to be more heat tolerant than both larvae and adults, with substantial genetic variation in heat resistance across RIL. Second, four QTLs were found for thermotolerance in eggs (QTL cytological ranges: 21C3-23E, 30A3-34C4, 64D-67A, 95C6-97F), and only one of these QTL (95C6-97F) co-localized (overlapped) with thermotolerance-QTL in larvae and adults. In addition, expression levels of some candidate genes within two large-effect QTL in adults (hsp60, hsc70-3, cátsup, ddc, trap1, CG10383, cyp6a13) correlated with heat-stress resistance in adults and larvae but not in eggs across RIL. All of the examined stages of the life cycle exhibited substantial genetic variation in heat-stress resistance, but the genetic basis of this variation in eggs is largely different from the genetic basis of thermotolerance in larvae and adults.