Detoxification Genes Differ Between Cactus-, Fruit-, and Flower-Feeding Drosophila

Area of Science:

• Genomics
• Evolutionary Biology
• Biochemistry

Background:

• Gene families involved in detoxification, such as carboxyl/cholinesterase, glutathione S-transferase, cytochrome P450, and UDP-glucuronosyltransferase, are crucial for adapting to diverse diets.
• Drosophila species exhibit varied host use, presenting an opportunity to study the genetic basis of adaptation.

Purpose of the Study:

• To investigate the association between gene family expansions and contractions in detoxification genes and host shifts across 14 Drosophila species.
• To identify specific gene families and evolutionary events (duplication, positive selection) linked to host specialization.

Main Methods:

• Comparative genomics analysis of annotated genomes from 14 Drosophila species.
• Quantification of gene copy numbers for four key detoxification gene families (carboxyl/cholinesterase, glutathione S-transferase, cytochrome P450, UDP-glucuronosyltransferase) and ABC transporters.
• Identification of positive selection events across these gene families.

Main Results:

• Species with specialized diets, like toxic fruit feeders (D. suzukii, M. citrifolia feeders), show significant expansions in certain detoxification gene families.
• ABC transporters display distinct expansion patterns, with D. elegans and D. hydei showing notable increases.
• Cactophilic specialists exhibit gene family reductions, contrasting with expansions in other species.
• 82 positive selection events were detected, with D. suzukii and D. sechellia showing a high proportion relative to branch length.
• Genes within detoxification-associated clades and specific genes like ABC transporter CG1718 and the α-esterase gene cluster were frequently involved in duplication and selection events.

Conclusions:

• Gene family evolution, including expansions and positive selection, is strongly associated with host shifts and dietary specialization in Drosophila.
• Detoxification gene families play a critical role in adapting to novel or toxic food sources.
• Specific genes and clades show recurrent involvement in adaptation, irrespective of host use, highlighting conserved adaptive mechanisms.