Identification and expression patterns of candidate carboxylesterases in Matsumura (Lepidoptera: Carposinidae), an important pest of fruit trees.

Matsumura (Lepidoptera: Carposinidae) is an important pest of fruit trees in a large area of Asia. The adults mainly depend on olfaction to communicate with the environment, but the olfactory mechanism has not been well known. Odorant degrading enzymes (ODEs) are important olfactory proteins, which inactivate and degrade odorants to free odorant receptors for maintaining olfactory sensitivity. Carboxylesterases (CXEs) are considered to be a major group of moth ODEs. In this study, four candidate CXEs (CXE1 ~ CXE4) were identified by using head transcriptomic data from adult females and males. Sequence alignment showed conserved amino acid residues and their variations in CXEs. Phylogenetic analysis indicated the CXEs with the variations cluster well, and each CXE clusters in a clade with some of the other lepidopteran CXEs, with a high enough bootstrap value. Gene expression analysis revealed that CXE2 and CXE3 have similar tissue and sex expression patterns in adults. The two CXEs have relatively high expression levels in the heads and are expressed more abundantly in the female heads than male heads. CXE1 and CXE4 are expressed at higher levels in the male heads than female heads, but not dominantly expressed in the heads among the different tissues. Whether these CXEs function as ODEs remains to be further researched. This study laid the foundation for exploring functions of CXEs.