Evolutionary Changes of GT1 Provide Insights Into the Adaptation of Butterflies to Plant Feeding.

Glycosyltransferase 1 (GT1) genes are involved in insect detoxification, olfactory perception, and endogenous metabolic regulation, and they play a role in the adaptation of butterflies to their specific feeding habits. However, their evolutionary trajectories in butterflies remain elusive. To reveal the evolutionary histories of the GT1 gene family and its relationship with feeding niches in butterflies, we systematically identified GT1 genes across 69 butterfly genomes and inferred their duplication and loss events by reconciling the gene tree with a species tree. Subsequently, the duplication modes and collinearity of these genes were determined between four selected species, followed by tests of selection pressures on the sites and branches of GT1 genes. In addition, the expression patterns of different GT1 gene subfamilies in the larval gut and adult antenna of two representative species were compared. Our results revealed substantial variation in the GT1 gene numbers among butterfly species, but no significant difference between generalists and specialists. Most GT1 genes originated via tandem duplications and are located within collinear blocks. Among the 13 subfamilies, the most expanded subfamilies, UGT33 and UGT40, harbored multiple positively selected sites, suggesting functional diversification. In addition, most GT1 genes expressed in adult antennae differ from those in larval guts, suggesting a divergence between female host selection and larval feeding preferences. Overall, the positive selection of specific sites and gene expression, not gene numbers or expansions, in the GT1 gene family is likely involved in the adaptation of plant utilization in butterflies. This study provides novel insights into the evolutionary mechanisms of detoxification-related gene families in insects and enhances our understanding of how butterflies adapt to chemical challenges posed by host plants.