L. Guo,Z.-D. Zhou,F. Mao,X.-Y. Fan,G.-Y. Liu,J. Huang,X.-M. Qiao
Drosophila suzukii (spotted wing drosophila) has become a major invasive insect pest of soft fruits in the America and Europe, causing severe yield losses every year. The female D. suzukii shows the oviposition preference for ripening or ripe fruit by cutting the hard skin with its serrated ovipositor. A recent study reported that mechanosensation is involved in the texture discrimination during egg-laying behaviour in D. suzukii . However, the underlying mechanism and molecular entity that control this behaviour are not known. The transient receptor potential (TRP) channels and degenerin/epithelial sodium channels (DEG/ENaC) are two candidate gene families of mechanically activated ion channels. Thus, we first identified TRP and DEG/ENaC genes in D. suzukii by bioinformatic analysis. Using transcriptome sequencing, we found that many TRP genes were expressed in the ovipositor in both D. suzukii and D. melanogaster , while some DEG/ENaCs showed species-specific expression patterns. Exposure to drugs targeting TRP and DEG/ENaC channels abolished the oviposition preference for harder texture in female D. suzukii . Therefore, mechanosensitive ion channels may play significant roles in the texture assessment of egg-laying behaviour in D. suzukii , which has promising implications to further research on the development of novel control measures.
Xiao-Li Bing,Zi-Jian Liang,Jia Tian,Xue Gong,Shao-Qiu Huang,Jie Chen,Xiao-Yue Hong
Insects are rich in various microorganisms, which play diverse roles in affecting host biology. Although most Drosophila species prefer rotten fruits, the agricultural pest Drosophila suzukii attacks ripening fruits before they are harvested. We have reported that the microbiota has positive and negative impacts on the agricultural pest D. suzukii on nutrient-poor and -rich diets, respectively. On nutrient-poor diets, microbes provide protein to facilitate larval development. But how they impede D. suzukii development on nutrient-rich diets is unknown. Here we report that Acetobacter pomorum (Apo), a commensal bacterium in many Drosophila species and rotting fruit, has several detrimental effects in D. suzukii . Feeding D. suzukii larvae nutrient-rich diets containing live Apo significantly delayed larval development and reduced the body weight of emerged adults. Apo induced larval immune responses and downregulated genes of digestion and juvenile hormone metabolism. Knockdown of these genes in germ-free larvae reproduced Apo-like weakened phenotypes. Apo was confirmed to secrete substantial amounts of gluconic acid. Adding gluconic acid to the D. suzukii larval diet hindered larval growth and decreased adult body weight. Moreover, the dose of gluconic acid that adversely affected D. suzukii did not negatively affect Drosophila melanogaster , suggesting that D. suzukii is less tolerant to acid than D. melanogaster . Taken together, these findings indicate that D. suzukii is negatively affected by gluconic acid, which may explain why it prefers ripening fruit over Apo-rich rotting fruit. These results show an insect's tolerance to microbes can influence its ecological niche.
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