Genome-wide analysis of carboxyl/cholinesterases (CCE) genes in Phenacoccus solenopsis

Carboxyl/cholinesterases (CCEs) are hydrolases converting carboxylic esters into acids and alcohols. Although CCE genes are systematically identified in 14 Hemipteran insects, the classification of CCEs is not performed in any Coccoidea insects. Here 77 CCE genes were categorized in a polyphagous Coccoidea herbivore, Phenacoccus solenopsis. Most CCEs had catalytic triad Ser-Asp/Glu-His, where serine formed a conserved sequence of GXSXG (X, any amino acid residue). Phylogenetic analysis and multiple sequence alignment revealed that 77 CCE genes fell into dietary/xenobiotic detoxification, hormone/pheromone processing and neuro/developmental function classes, including 32 α-esterases (AEs), 22 β-esterases (BEs), 9 juvenile hormone esterases (JHEs), 2 acetylcholinesterases (ACEs), 2 glutactins, 8 neuroligins and 1 glioactin. Genomic distribution and collinearity analysis, along with phylogenetic analysis, showed that a total of 12 tandem duplication events within the CCE gene family occurred in whole genome. Intron-exon structure analysis discovered there was an intronless PsCCE gene. Long PsCCEs had more exon and intron numbers. Moreover, several tandemly duplicated PsCCEs possessed identical or similar exon numbers. All CCEs were actively transcribed throughout the development and 73 CCEs were expressed when the larvae feeding on three host plants estimated by RPKM values. PsAE7, PsAE9 and PsJHE9 were only expressed in males. Therefore, a framework of information on CCE genes was established in P. solenopsis. The results facilitate exploring the resistant modes to environmental toxins.