Identification of carboxylesterase genes and their expression profiles in the Colorado potato beetle Leptinotarsa decemlineata treated with fipronil and cyhalothrin.

Based on the Leptinotarsa decemlineata transcriptome dataset and the GenBank sequences, 70 novel carboxylesterases and 2 acetylcholinesterases were found. The 72 members belong to a multifunctional carboxylesterase/cholinesterase superfamily (CCE). A phylogenetic tree including the 72 LdCCEs and the CCEs from Tribolium castaneum, Drosophila melanogaster and Apis mellifera revealed that all CCEs fell into three main phylogenetic groups: dietary/detoxification, hormone/semiochemical processing, and neurodevelopmental classes. Numbers of L. decemlineata CCEs in the three classes were 52, 12 and 8, respectively. The dietary/detoxification class includes two clades: coleopteran xenobiotic metabolizing and α-esterase type CCEs. CCEs in the two clades have independently expanded in L. decemlineata. The hormone/semiochemical processing class has three clades: integument CCEs, β- and pheromone CCEs and juvenile hormone CCEs. Integument CCEs in L. decemlineata have also expanded. The neurodevelopmental CCEs are implicated the most ancient class, containing acetylcholinesterase, neuroligin, neurotactin, glutactin, gliotactin and others. Among the 70 novel CCE genes, KM220566, KM220530, KM220576, KM220527 and KM220541 were fipronil-inducible, and KM220578, KM220566, KM220542, KM220564, KM220561, KM220554, KM220527, KM220538 and KM220541 were cyhalothrin-inducible. They were the candidates involving in insecticide detoxification. Moreover, our results also provided a platform to understand the functions and evolution of L. decemlineata CCE genes.