Patterns of longevity and fecundity at two temperatures in a set of heat-selected recombinant inbred lines of Drosophila melanogaster

Abstract

Quantitative trait loci (QTL) were mapped for longevity and fecundity at two temperatures, 20 and 30 °C, in two sets of recombinant inbred lines (RIL) highly differing in thermotolerance. Early fecundity (EF) and longevity showed a negative association between temperatures. For instance, longevity was higher and fecundity was lower in the RIL panel showing higher life span at 30 °C. One X-linked QTL (7B3-12E) co-localized for longevity and EF at 20 °C, with one QTL allele showing a positive additive effect on longevity and a negative effect on EF. The across-RIL genetic correlation between longevity and EF was not significant within each temperature, and most QTL that affect life span have no effect on EF at each temperature. EF and longevity can mostly be genetically uncoupled in the thermotolerance-divergent RIL within each temperature as opposed to between temperatures. QTL were mostly temperature specific, although some trait-specific QTL showed possible antagonistic effects between temperatures.

Thermal‐specific patterns of longevity and fecundity in a set of heat‐sensitive and heat‐resistant genotypes of Drosophila melanogaster

“…The oviposition surface consisted of a solution of agar (1.5 g) and water (140 ml) plus 0.2 ml of food coloring and yeast paste. Food coloring (Fleibor Laboratory, La Tablada, Buenos Aires, Argentina) was added to facilitate the observation of all eggs and egg shells (Sambucetti et al., ). The eggs were counted on the spoons using a stereo microscope every 2 days, when flies were transferred to new vials with fresh spoons.…”

“…Several QTL mapping studies revealed some potentially pleiotropic regions with effects on both stress resistance and longevity (Vieira et al., ; Wang et al., ; Defays et al., ; Rodriguez et al., ; Sambucetti et al., ), suggesting an association of the genetic variation for stress resistance with longevity. Previous studies in Drosophila melanogaster Meigen (Diptera: Drosophilidae) have found a major QTL affecting heat resistance in the middle of chromosome 2 (Norry et al., , 2007a, ; Morgan & Mackay, ; Arias et al., ).…”

“…Some candidate genes included within these QTLs are associated with stress resistance in Drosophila (e.g., trap1 , catsup , ddc , hsp60 , hsc70 ; Norry et al., ). Some temperature‐specific QTL for longevity co‐localize with heat‐resistance QTL (Sambucetti et al., ). For example, the X‐linked QTL mentioned above has an allele with positive effects on both KRHT (knockdown resistance to high temperature) and longevity at high temperature, indicating that the QTL conferring heat resistance also increases longevity at high temperature (Sambucetti et al., ).…”

“…Some temperature‐specific QTL for longevity co‐localize with heat‐resistance QTL (Sambucetti et al., ). For example, the X‐linked QTL mentioned above has an allele with positive effects on both KRHT (knockdown resistance to high temperature) and longevity at high temperature, indicating that the QTL conferring heat resistance also increases longevity at high temperature (Sambucetti et al., ). In spite of these possible links between heat resistance and longevity, the possible effects of heat‐resistance genotypes remains to be explored on other fitness traits, such as fecundity in Drosophila .…”

“…Given the well‐known association between longevity and fecundity, it is interesting to test these two classes of traits for their possible associations to heat‐resistance genotypes at elevated temperature (e.g., Loeschcke et al., ). QTL mapping in recombinant inbred lines (RIL) from crosses between heat‐selected populations provided information about genomic regions affecting heat resistance (Norry et al., , 2007a, ; Morgan & Mackay, ; Arias et al., ; Sambucetti et al., ), as well as longevity and fecundity (Defays et al., ; Sambucetti et al., ; Highfill et al., ). This information can be used to establish fly stocks with alternative genotypes for heat resistance, which can be used to test fitness‐related traits of individuals carrying heat‐sensitive genotypes in comparison to individuals carrying heat‐resistant genotypes (e.g., Loeschcke et al., ).…”