RNA interference of acetylcholinesterase in the Asian citrus psyllid, Diaphorina citri, increases its susceptibility to carbamate and organophosphate insecticides

Abstract

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Lividae) transmits the Candidatus Liberibacter asiaticus, which causes citrus greening disease or Huanglongbing, (HLB). To date, there is no efficient cure for HLB disease and the control of D. citri using insecticides became the most important tools for the management of HLB. However, the extensive use of insecticides could increase D. citri resistance to these insecticides. The objective of this study was to investigate the effect of RNA interference of acetylcholinesterase (AChE) on the mortality and susceptibility of D. citri to the four major insecticides used in Florida. In this study, we used a consensus sequence derived from the two AChE genes and cholinesterase 2-like (ChE-2-like) gene to target all of the three genes. Treatment with dsRNA-AChE increased the mortality percentages of both nymphs and adults of D. citri. The mortality percentage increased with the increase in the concentration of applied dsRNA-AChE, and the highest mortality (> 60%) was observed at the highest applied concentration (125ng/μl). Treatments of nymphs or adults with dsRNA-AChE down-regulated the expression of the three targeted genes of D. citri. Silencing of AChE and ChE in D. citri nymphs increased the susceptibility of emerged adults to chlorpyrifos and carbaryl, which act as AChE inhibitors. However, treatment with dsRNA-AChE did not increase the susceptibility of emerged adults to imidacloprid, which acts as an agonist of nicotinic acetylcholine receptors. In the same manner, treatment of adults with dsRNA-AChE increased their susceptibility to chlorpyrifos and carbaryl, but did not affect their susceptibility to imidacloprid. The ANOVA did not show any significant increase in susceptibility of D. citri adults to fenpropathrin after treatment with dsRNA-AChE, either as nymphs or as adults. However, simple linear regression showed that treatment with dsRNA-AChE increased D. citri susceptibility to fenpropathrin, which indicated that AChE could be involved in the metabolism of fenpropathrin. Our results indicated that silencing of AChE and ChE genes in D. citri to increase its susceptibility to insecticides could be a promising tool for the control of this important vector.

Identification of detoxification genes in imidacloprid‐resistant Asian citrus psyllid (Hemiptera: Lividae) and their expression patterns under stress of eight insecticides

“…To confirm the function of the six overexpressed detoxification genes in imidacloprid resistance, the RNAi were used to silence these overexpressed detoxification genes in the imidacloprid‐resistant strain. By using an RNAi‐mediated approach (topical feeding application), it was demonstrated that five CYP4 genes ( CYP4C67 , CYP4DA1 , CYP4C68 , CYP4G70 and CYP4DB1 ) confer imidacloprid resistance in ACP, and that silencing acetylcholinesterase increased the mortality of ACP in response to carbaryl treatment . A similar RNAi delivery method was also reported in Ostrinia nubilalis larvae .…”

“…In addition, RNase‐free water and dsRNA‐gfp (100 µg mL −1 ) were used as controls. RNAi experiments were performed by the topical feeding application described by Kishk and Killiny . Briefly, ACP newly emerged adults from the imidacloprid‐resistant strain were starved for 4 h and were anaesthetized with a short puff of CO 2 before the application dsRNA.…”

“…The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is a serious pest in citrus throughout the world. This insect directly damages plants by feeding on sap and indirectly damages plants by transmitting the phloem‐limited bacterium Candidatus Liberibacter asiaticus ( C las), which causes huanglongbing (HLB) or citrus greening disease, which is the most fatal citrus disease worldwide. ACP is susceptible to a number of insecticide classes, and the use of insecticides to control ACP is the most effective strategy to prevent the spread of HLB …”

“…The ESTs and GSTs also play a central role in detoxification of insecticides . Some research reported that the knockdown of ESTs and GSTs in ACP leads to increased susceptibility to insecticides . Nevertheless, no EST and GST genes have been reported to be responsible for imidacloprid resistance in ACP.…”

Resistance Potential of <i>Chrysoperla carnea</i> (Stephens) to Insecticides Used Against Sucking Complex of Cotton

“…It is usually responsible for degradation of excitatory neurotransmitter, acetylcholine, thereby termination of nerve impulse transmission at cholinergic synapses [31], which is critical to the functioning of the insect nervous system [29,32]. Once this enzyme is inhibited, acetylcholine builds up and insect expire from overstimulation of their nervous system [33].…”