Sun Liang, Wang Qian, Wang Qi, Zhang Yuxing, Tang Meijun, Guo Huawei, Fu Jianyu, Xiao Qiang, Zhang Yanan, Zhang Yongjun
Key Laboratory of Tea Quality and Safety Control, Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China.
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
Front Physiol. 2017 Dec 18;8:1085. doi: 10.3389/fphys.2017.01085. eCollection 2017.
Carboxylesterases (CXEs) belong to a family of metabolic enzymes. Some CXEs act as odorant-degrading enzymes (ODEs), which are reportedly highly expressed in insect olfactory organs and participate in the rapid deactivation of ester pheromone components and plant volatiles. The tea geometrid Prout produces sex pheromones consisting of non-ester functional compounds but relies heavily on acetic ester plant volatiles to search for host plants and locate oviposition sites. However, studies characterizing putative candidate ODEs in this important tea plant pest are still relatively scarce. In the present study, we identified 35 candidate genes from chemosensory organs based on previously obtained transcriptomic data. The deduced amino acid sequences possessed the typical characteristics of the insect CXE family, including oxyanion hole residues, the Ser-Glu-His catalytic triad, and the Ser active included in the conserved pentapeptide characteristic of esterases, Gly-X-Ser-X-Gly. Phylogenetic analyses revealed that the EoblCXEs were diverse, belonging to several different insect esterase clades. Tissue- and sex-related expression patterns were studied via reverse-transcription and quantitative real-time polymerase chain reaction analyses (RT- and qRT-PCR). The results showed that 35 genes presented a diversified expression profile; among these, 12 appeared to be antenna-biased, two were non-chemosensory organ-biased, 12 were ubiquitous, and nine showed heterogeneous expression levels among different tissues. Intriguingly, two genes, and , were not only strongly localized to antennal sensilla tuned to odorants, such as the sensilla trichodea (Str I and II) and sensilla basiconica (Sba), but were also expressed in the putative gustatory sensilla styloconica (Sst), indicating that these two CXEs might play multiple physiological roles in the chemosensory processing system. This study provides the first elucidation of CXEs in the chemosensory system of a geometrid moth species and will enable a more comprehensive understanding of the functions of insect CXEs across lepidopteran species.
羧酸酯酶（CXEs）属于一类代谢酶。一些CXEs作为气味降解酶（ODEs），据报道在昆虫嗅觉器官中高度表达，并参与酯类信息素成分和植物挥发物的快速失活。茶尺蠖Prout产生由非酯功能化合物组成的性信息素，但在寻找寄主植物和定位产卵地点时严重依赖乙酸酯类植物挥发物。然而，关于这种重要茶树害虫中假定的候选ODEs的研究仍然相对较少。在本研究中，我们基于先前获得的转录组数据从化学感受器官中鉴定出35个候选基因。推导的氨基酸序列具有昆虫CXE家族的典型特征，包括氧阴离子洞残基、Ser-Glu-His催化三联体以及酯酶保守五肽特征中的Ser活性位点Gly-X-Ser-X-Gly。系统发育分析表明，茶尺蠖CXEs具有多样性，属于几个不同的昆虫酯酶分支。通过逆转录和定量实时聚合酶链反应分析（RT-和qRT-PCR）研究了组织和性别相关的表达模式。结果表明，35个基因呈现出多样化的表达谱；其中，12个表现出触角偏向性，2个偏向于非化学感受器官，12个在各处均有表达，9个在不同组织中的表达水平存在差异。有趣的是，两个基因， 和 ，不仅强烈定位于对气味有反应的触角感器，如毛形感器（Str I和II）和锥形感器（Sba），还在假定的味觉栓锥形感器（Sst）中表达，这表明这两个CXEs可能在化学感受处理系统中发挥多种生理作用。本研究首次阐明了尺蛾科蛾类化学感受系统中的CXEs，将有助于更全面地了解鳞翅目昆虫中昆虫CXEs的功能。
