Zhang Jianqin, Ge Pingting, Li Daqi, Guo Yaping, Zhu Kun Yan, Ma Enbo, Zhang Jianzhen
Research Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi 030006, China.
Department of Entomology, 123 Waters Hall, Kansas State University, Manhattan, KS 66506, USA.
J Insect Physiol. 2015 Jun;77:1-8. doi: 10.1016/j.jinsphys.2015.03.013. Epub 2015 Apr 1.
Carboxylesterases (CarEs) play a crucial role in detoxification of xenobiotics and resistance to insecticides in insects. In this study, two cDNAs of CarE genes (LmCesA4 and LmCesA5) were sequenced from the migratory locust, Locusta migratoria. The cDNAs of LmCesA4 and LmCesA5 putatively encoded 538 and 470 amino acid residues, respectively. The deduced amino acid sequences of the two CarE genes showed 45.0% identities, possessed highly conserved catalytic triads (Ser-Glu-His), and clustered in phylogenetic analysis. These results suggest that they are homologous genes. Both CarE genes were expressed throughout the developmental stages. However, LmCesA4 was predominately expressed in the midgut (including the gastric caeca) and fat bodies, whereas LmCesA5 was mainly expressed in the gastric caeca. The in situ hybridization results showed that the transcripts of the two genes were localized in apical and basal regions of the columnar cells in the gastric caeca. Gene silencing followed by insecticide bioassay increased the mortalities of deltamethrin-, malathion-, and carbaryl-treated locusts by 29.5%, 31.0% and 20.4%, respectively, after the locusts were injected with LmCesA4 double-stranded RNA (dsRNA). In contrast, the injection of LmCesA5 dsRNA did not significantly increase the susceptibility of the locusts to any of these insecticides. These results suggest that these genes not only show different tissue expression patterns but also play different roles in insecticide detoxification.
羧酸酯酶（CarEs）在昆虫对外源化合物的解毒作用及对杀虫剂的抗性中发挥着关键作用。在本研究中，从飞蝗Locusta migratoria中测序得到了两个羧酸酯酶基因（LmCesA4和LmCesA5）的cDNA。LmCesA4和LmCesA5的cDNA分别推测编码538和470个氨基酸残基。这两个羧酸酯酶基因推导的氨基酸序列显示出45.0%的同一性，具有高度保守的催化三联体（丝氨酸-谷氨酸-组氨酸），并且在系统发育分析中聚类。这些结果表明它们是同源基因。两个羧酸酯酶基因在整个发育阶段均有表达。然而，LmCesA4主要在中肠（包括胃盲囊）和脂肪体中表达，而LmCesA5主要在胃盲囊中表达。原位杂交结果表明，这两个基因的转录本定位在胃盲囊中柱状细胞的顶端和基部区域。在用杀虫剂生物测定法进行基因沉默后，向飞蝗注射LmCesA4双链RNA（dsRNA）后，溴氰菊酯、马拉硫磷和西维因处理的飞蝗死亡率分别提高了29.5%、31.0%和20.4%。相比之下，注射LmCesA5 dsRNA并未显著提高飞蝗对这些杀虫剂中任何一种的敏感性。这些结果表明，这些基因不仅表现出不同的组织表达模式，而且在杀虫剂解毒中发挥着不同的作用。
