Evolution of GSTD1 in Cactophilic Drosophila

Area of Science:

• * Evolutionary biology
• * Molecular genetics
• * Insect adaptation

Background:

• * Glutathione S-transferase D1 (GSTD1) plays a key role in detoxifying xenobiotics and adapting to new food sources.
• * GSTD1 is implicated in host-plant adaptation in Drosophila, particularly in species shifting to new cactus hosts.
• * The repleta group of Drosophila offers a model for studying ecological genetics of adaptation.

Purpose of the Study:

• * To investigate population genetic and molecular evolution of the GstD1 gene in nine Drosophila species.
• * To analyze the association of GstD1 evolution with different cactus host plants (Opuntia vs. Columnar).
• * To identify signatures of selection and molecular changes in GstD1 related to adaptation.

Main Methods:

• * Population genetic analyses of the GstD1 gene.
• * Molecular evolution analyses, including tests for selective sweeps and positive selection.
• * Sequence analysis of GstD1 in nine Drosophila species associated with different cacti.

Main Results:

• * Strong evidence of selection was detected in the GstD1 gene of Drosophila hexastigma.
• * D. hexastigma GstD1 sequences exhibit a recent selective sweep and positive selection at residue 116 (Q116T).
• * This substitution outside the active site causes a conformational change, potentially enhancing substrate binding.

Conclusions:

• * GSTD1 in D. hexastigma has likely evolved improved substrate binding capabilities.
• * This adaptation is crucial for coping with the chemically diverse columnar cactus environments inhabited by this species.
• * The study highlights GSTD1 as a target for adaptation in Drosophila species diversifying their diets.