Silencing fatty acyl-CoA reductase with dsRNA damaged the lipid-based cuticle barrier in Locusta migratoria

Cuticular hydrocarbons (CHCs) prevent massive water loss and are therefore essential for insect survival in scorching and dry environments. Locusta migratoria, a widespread agricultural pest, is exposed to elevated temperatures in its natural habitat. To understand the molecular mechanisms in L. migratoria against desiccation, we identified and characterized a fatty acyl-CoA reductase gene (LmFAR). LmFAR was highly expressed in the integument and fat body. Moreover, we found that LmFAR protein was localized in oenocytes. After suppressing LmFAR, over 90 % locusts died with a reduction of body water content. The procuticle structure of dsLmFAR treated insects was loose and cuticle barrier was disrupted, suggesting that FAR products are important to incorporate into the chitin matrix. dsLmFAR treated locusts showed increased sensitivity to desiccation conditions, xenobiotics and insecticides penetration was facilitated. CHC quantification by GC-MS analysis and in situ lipid detection by Bodipy both indicated that knockdown of LmFAR resulted in a decrease in total cuticle lipid amounts. In conclusion, LmFAR contributes to normal CHC amounts and cuticle integrity in locusts, thereby contributing to their adaptation to water variation.