The choreography of the chemical defensome response to insecticide stress: insights into the Anopheles stephensi transcriptome using RNA-Seq

Abstract

Animals respond to chemical stress with an array of gene families and pathways termed “chemical defensome”. In arthropods, despite many defensome genes have been detected, how their activation is arranged during toxic exposure remains poorly understood. Here, we sequenced the transcriptome of Anopheles stephensi larvae exposed for six, 24 and 48 hours to the LD50 dose of the insecticide permethrin to monitor transcriptional changes of defensome genes across time. A total of 177 genes involved in insecticide defense were differentially expressed (DE) in at least one time-point, including genes encoding for Phase 0, I, II, III and antioxidant enzymes and for Heat Shock and Cuticular Proteins. Three major patterns emerged throughout time. First, most of DE genes were down-regulated at all time-points, suggesting a reallocation of energetic resources during insecticide stress. Second, single genes and clusters of genes turn off and on from six to 48 hours of treatment, showing a modulated response across time. Third, the number of up-regulated genes peaked at six hours and then decreased during exposure. Our results give a first picture of how defensome gene families respond against toxicants and provide a valuable resource for understanding how defensome genes work together during insecticide stress.

Regulating resistance: CncC:Maf, antioxidant response elements and the overexpression of detoxification genes in insecticide resistance

“…Exposure to insecticide instigates a complex response through which insects sequester, detoxify or excrete toxins before they reach their target or have other adverse consequences. The battery of detoxification genes and those elements which control their coordinated response has been labelled the defensome [1]. The insect defensome must cope with a variety of assaults from foodstuffs e.g.…”

High throughput sequencing reveals Drosophila suzukii responses to insecticides

“…The higher number of significantly DEGs identified in Pierce population when compared to Clarke population flies correlates with the higher LC 50 values calculated for Pierce county flies. DEGs could reflect a combination of a selective effect yielding gene transcripts enriched in flies surviving the insecticide treatment, and an inductive effect, referred to as the defensome which occurs in animals during the treatment period in response to toxicants (Niu et al, 2012;De Marco et al, 2017).…”

Adenosine Triphosphate–Binding Cassette Transporters Are Not Involved In the Detoxification of Azadirachta indica Extracts In Anopheles stephensi Larvae

“…Azadirachta indica and other Meliaceae species have shown strong larvicidal, antiemergence, repellency, and antioviposition effects in different mosquito species (Mulla and Su 1999). It is now known that, in several mosquito species, part of the detoxification process against xenobiotics is mediated by adenosine triphosphatebinding cassette (ABC) transporters on Anopheles stephensi Liston (Epis et al 2014a(Epis et al , 2014bPorretta et al 2016;De Marco et al 2017;Mastrantonio et al 2017); Anopheles gambiae Giles (Nkya et al 2014); Aedes aegypti (L.) (Bariami et al 2012); and Aedes albopictus (Skuse) (Esquivel et al 2016). In particular, on An.…”

“…In particular, on An. stephensi it has been demonstrated that, among the 8 subfamilies (from A to H) of ABC transporters existing in insects, the B and G subfamilies play a major role in the detoxification of permethrin, showing a pattern of response that varies with time (Epis et al 2014a(Epis et al , 2014bDe Marco et al 2017;Mastrantonio et al 2017). Despite their importance against pyrethroids, these genes are not differentially expressed in response to larval exposure to temephos, a widely used larvicide, highlighting an insecticide-specific involvement of the transporters in this mosquito species (Porretta et al 2016).…”

“…Their mortality results were supported by RT-PCR data, showing a differential expression of the genes analyzed, in particular ABCG4 and ABCmember6. The overexpression peak of these 2 genes was detected after 6 h exposure, but the up-regulation persisted after 24 h. The other genes taken into account were down-regulated or not differentially expressed at the different time points (Epis et al 2014a(Epis et al , 2014bDe Marco et al 2017). In the present study, the analysis of RT-PCR data did not reveal any effect of neem treatment on ABC genes' expression: treated sample DCt values were not significantly different from controls, for any of the 6 target genes and any of the dose-time combinations (all P .…”