Desiccation resistance: effect of cuticular hydrocarbons and water content inDrosophila melanogasteradults

Abstract

BackgroundThe insect cuticle covers the whole body and all appendages and has bi-directionnal selective permeability: it protects against environmental stress and pathogen infection and also helps to reduce water loss. The adult cuticle is often associated with a superficial layer of fatty acid-derived molecules such as waxes and long chain hydrocarbons that prevent rapid dehydration. The waterproofing properties of cuticular hydrocarbons (CHs) depend on their chain length and desaturation number. Drosophila CH biosynthesis involves an enzymatic pathway including several elongase and desaturase enzymes.MethodsThe link between desiccation resistance and CH profile remains unclear, so we tested (1) experimentally selected desiccation-resistant lines, (2) transgenic flies with altered desaturase expression and (3) natural and laboratory-induced CH variants. We also explored the possible relationship between desiccation resistance, relative water content and fecundity in females.ResultsWe found that increased desiccation resistance is linked with the increased proportion of desaturated CHs, but not with their total amount. Experimentally-induced desiccation resistance and CH variation both remained stable after many generations without selection. Conversely, flies with a higher water content and a lower proportion of desaturated CHs showed reduced desiccation resistance. This was also the case in flies with defective desaturase expression in the fat body.DiscussionWe conclude that rapidly acquired desiccation resistance, depending on both CH profile and water content, can remain stable without selection in a humid environment. These three phenotypes, which might be expected to show a simple relationship, turn out to have complex physiological and genetic links.

Peer Review #3 of "The cuticle inward barrier in Drosophila melanogaster is shaped by mitochondrial and nuclear genotypes and a sex-specific effect of diet (v0.1)"

“…Likewise, it has previously been demonstrated that diet does control the efficiency of the outward barrier, probably by influencing the amounts and, importantly, the composition of CHCs (Fedina et al, 2012). In line with this work, a recent study reported that the proportion of desaturated CHCs defines the efficiency of the barrier against desiccation (Ferveur et al, 2018).…”

Desiccation Resistance and Micro-Climate Adaptation: Cuticular Hydrocarbon Signatures of Different Argentine Ant Supercolonies Across California

“…Nevertheless, similar correlative effects with environmental factors have been found, with the total amount of n-alkenes showing a positive correlation with temperature and n-alkanes showing a negative correlation with humidity (Woodrow et al 2000). Moreover, it has recently been demonstrated in Drosophila fruit flies that increased proportions of n-alkenes and alkadienes are linked to increased resistance to desiccation, hinting at similar adaptive mechanisms for n-alkenes as in L. humile, allowing for acclimatization to related climatic conditions (Ferveur et al 2018).…”

“…For the corresponding correlation graphs and test statistics of each of the individual CHCs see Supplementary Fig. 2 and Supplementary Table 1 2015; Ferveur et al 2018). Trimethyl alkanes, on the other hand, showed the reverse correlation, being negatively correlated with monthly average temperature, but positively with monthly average precipitation (Fig.…”

Inhibition of fatty acid desaturation impairs cuticle differentiation in Drosophila melanogaster

“…It has been reported recently that desiccation susceptibility in adult D. melanogaster is due to a general physiological constitution involving Desat1 function rather than directly depending on desaturation of surface CHCs (Ferveur, Cortot, Rihani, Cobb, & Everaerts, ). To test for this possibility in our experiments, we determined the water content of control ( n = 398) and CAY10566‐fed larvae ( n = 412).…”

“…By contrast, Desat1 is essential for viability. It is expressed at all stages and is among others involved in the synthesis of desaturated CHCs (Ferveur et al, ; Wang et al, ). Interestingly, the cuticle barrier efficiency depends on the ratio of desaturated to saturated CHCs, rather than on the total amounts of desaturated CHC.…”