RESUMEN
The juvenile hormone binding protein (JHBP) and takeout (TO) genes, mediated by the juvenile hormone (JH), play a crucial role in regulating the reproductive physiology of insects. Our previous study revealed that spinosad-resistant Frankliniella occidentalis (NIL-R) exhibited reduced fecundity and significant changes in JHBP/TO family gene expression. We hypothesized that these genes were involved in regulating the fitness costs associated with resistance. In this study, 45 JHBP/TO genes were identified in F. occidentalis, among which FoTO2 and FoTO10 were duplicates. Additionally, eight genes exhibited significant down-regulation in the NIL-R population. Two genes (FoTO6 and FoTO24) that exhibited the most significant differential expression between the spinosad-susceptible (Ivf03) and NIL-R populations were selected to investigate their roles in resistance fitness using RNA interference (RNAi). Following interference with FoTO6, FoTO24, and their combination, the expression levels of vitellogenin (Vg) were downregulated by 3%-30%, 13%-28%, and 14%-32% from the 2nd day to the 5th day, respectively; Krüppel-homolog 1 (Kr-h1) expression was down-regulated by 3%-65%, 11%-34%, and 11%-39% from the 2nd day to the 5th day, respectively; ovariole length was shortened by approximately 18%, 21%, and 24%, respectively; and the average number of eggs decreased from 407 to 260, 148, and 106, respectively. Additionally, a JH supplementation experiment on the NIL-R population revealed that the expression levels of both FoTO6, FoTO24, Vg and Kr-h1 were significantly upregulated compared with those observed in the Ivf03 population, resulting in increased fecundity. These results suggest that FoTO6 and FoTO24 are involved in JH-mediated regulation of the reproductive fitness cost of resistance to spinosad. Further, FoTO6 and FoTO24 can be considered potential target genes for applying RNAi technology in the scientific management of F. occidentalis.
Asunto(s)
Proteínas de Insectos , Resistencia a los Insecticidas , Thysanoptera , Animales , Resistencia a los Insecticidas/genética , Proteínas de Insectos/genética , Proteínas de Insectos/metabolismo , Thysanoptera/genética , Thysanoptera/fisiología , Thysanoptera/efectos de los fármacos , Insecticidas/farmacología , Femenino , Reproducción/genética , Macrólidos/farmacología , Vitelogeninas/genética , Vitelogeninas/metabolismo , Combinación de Medicamentos , Hormonas Juveniles/metabolismo , Hormonas Juveniles/farmacología , Interferencia de ARN , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Aptitud GenéticaRESUMEN
BACKGROUND: The western flower thrips Frankliniella occidentalis, a worldwide agricultural pest, has developed resistance to an array of insecticides. Spinosad resistance confers an apparent fitness cost in F. occidentalis. In the present study, we compared the reproductive capacities, ovary development, and the expression of the vitellogenin (Vg) gene in spinosad-susceptible (Ivf03) and -resistant (NIL-R) near isogenetic lines of F. occidentalis in order to clarify the reason for the fitness cost in spinosad resistance. RESULTS: The NIL-R strain exhibited a 17.9% decrease in fecundity (eggs laid per female) as compared to the Ivf03 strain, and the ovariole was significantly shortened by 2.8% in the NIL-R strain relative to the Ivf03 strain. Compared to the Ivf03 strain, the expression levels of Vg mRNA and protein were downregulated by 33.7% and 32.9% in the NIL-R strain, respectively. Moreover, interference with the Vg gene significantly reduced the expression levels of Vg mRNA and protein, and decreased ovariole length, survival rates and the fecundity of both strains. CONCLUSION: The results indicate that the downregulated expression of Vg may contribute to the reduction of ovariole length and consequently to a fitness cost in spinosad-resistant F. occidentalis. The results not only increase our understanding of the evolution of insecticide resistance, but also could contribute to the formulation of control strategy of F. occidentalis. © 2022 Society of Chemical Industry.
Asunto(s)
Insecticidas , Thysanoptera , Femenino , Animales , Vitelogeninas/genética , Insecticidas/farmacología , Macrólidos/farmacología , Resistencia a los Insecticidas/genéticaRESUMEN
Although esterase-mediated spinosad resistance has been proposed for several insects, the associated molecular mechanism remains poorly understood. In this study, we investigated the mechanism of esterase-based spinosad resistance in house flies using a susceptible strain (SSS) and a spinosad-resistant, near-isogenic line (N-SRS). Combined with the synergistic effect of DEF on spinosad in the N-SRS strain, decreased ali-esterase activity in the spinosad-resistant strain has implicated the involvement of mutant esterase in spinosad resistance in house flies. Examination of the carboxylesterase gene MdαE7 in the two strains revealed that four non-synonymous mutations (Trp251-Leu, Asp273-Glu, Ala365-Val, and Ile396-Val) may be associated with spinosad resistance in house flies. Single nucleotide polymorphism analysis further indicated a strong relationship between these four mutations and spinosad resistance. Moreover, quantitative real-time PCR revealed a female-linked MdαE7 expression pattern in the N-SRS strain, which may contribute to sex-differential spinosad resistance in house flies.
Asunto(s)
Moscas Domésticas/fisiología , Resistencia a los Insecticidas/genética , Insecticidas/toxicidad , Macrólidos/toxicidad , Animales , Carboxilesterasa/metabolismo , Combinación de Medicamentos , Femenino , Moscas Domésticas/efectos de los fármacosRESUMEN
Females developed notably higher resistance than males in a spinosad-resistant house fly strain, however, resistance factors responsible for this phenomenon are poorly understood. In this study, the potential role of cytochrome P450 monooxygenases involved in the sex-differential spinosad resistance in house flies was investigated, using a susceptible strain (SSS) and a spinosad resistant near-isogenic line (N-SRS). Combination of the synergism of spinosad by PBO and increased cytochrome P450 monooxygenase activity in the N-SRS strain implied that cytochrome P450 monooxygenases contributed to spinosad resistance in house flies. Transcriptional levels of eight P450 genes related to insecticide resistance in two genders of the SSS and N-SRS strain were separately evaluated by quantitative real-time PCR. Notably, compared with the corresponding gender of susceptible SSS house flies, CYP4G2 and CYP6A5v2 were overexpressed in resistant N-SRS females, while the expression of these two P450 genes was significantly decreased in resistant N-SRS males. Furthermore, by measuring the expression of CYP4G2 and CYP6A5v2 in female and male house fly populations with different spinosad resistance levels, which were generated from a series of genetic crosses, the genetic linkage between spinosad resistance and P450 gene expression was analyzed. It was found that with increased spinosad resistance, CYP4G2 and CYP6A5v2 were up-regulated in females, while both of them were down-regulated in males, and this suggested their involvement in the female-linked spinosad resistance of house flies. Taken together, our results provide valuable insight into the involvement of cytochrome P450 monooxygenases in the sex-differential spinosad resistance in house flies.
Asunto(s)
Sistema Enzimático del Citocromo P-450/metabolismo , Moscas Domésticas/efectos de los fármacos , Macrólidos/farmacología , Muscidae/efectos de los fármacos , Animales , Sistema Enzimático del Citocromo P-450/genética , Combinación de Medicamentos , Femenino , Resistencia a los Insecticidas/genética , MasculinoRESUMEN
Nicotinic acetylcholine receptors (nAChRs), a molecular target for spinosyns and neonicotinoids, mediate rapid cholinergic transmission in insect central nervous system by binding acetylcholine. Previous studies have shown that mutations in nAChRs contribute to the high level of resistance to these two classes of insecticides. In this study, we identified nine nAChR subunits from a transcriptome of the western flower thrips, Frankliniella occidentalis, including α1-7, ß1, and ß2. Exon 4 of α4 and exons 3 and 8 of α6 each have two splicing variants, respectively. In addition, altered or incorrect splicing leads to truncated forms of α3, α5, and α6 subunits. The abundance of every nAChRs in both spinosad susceptible and resistant strains was highest in the 1st instar nymph. Significantly more truncated forms of α6 subunit were detected in spinosad resistant strains, whereas, hardly any full-length form was found in the two highly resistant F. occidentalis strains (resistance ratio >104-fold). Under laboratory conditions, spinosad resistance was positively correlated with truncated α6 transcripts. The correlation was later confirmed under the field conditions using five field strains. As the molecular target of spinosad, the percentage of truncated nAChR α6 subunits can be used as a diagnostic tool to detect and quantify spinosad resistance in the field.
Asunto(s)
Resistencia a Medicamentos/efectos de los fármacos , Proteínas de Insectos , Macrólidos/farmacología , Receptores Nicotínicos , Animales , Combinación de Medicamentos , Resistencia a Medicamentos/genética , Proteínas de Insectos/genética , Proteínas de Insectos/metabolismo , Neoptera/genética , Neoptera/metabolismo , Receptores Nicotínicos/genética , Receptores Nicotínicos/metabolismoRESUMEN
Frankliniella occidentalis (Pergande) is an economically important pest of agricultural crops. High resistance has been detected in field populations of F. occidentalis against the insecticide spinosad. In this study, we compared life history traits, body sizes, and feeding behaviors (recorded via an electrical penetration graph) of spinosad-susceptible (Ivf03) and spinosad-resistant (NIL-R) near-isogenic lines of F. occidentalis. Life table analysis showed that NIL-R had reduced female longevity and reduced fecundity. The relative fitness of NIL-R (0.43) was less than half that of Ivf03. NIL-R individuals were smaller than Ivf03 individuals, both in body length and body width at every stage. The number and duration of feeding activities were significantly reduced in NIL-R, with the exception of total duration of long-ingestion probes. These results suggest that there is a fitness trade-off associated with spinosad resistance in F. occidentalis, and that the development of resistance in this pest species may be reduced by rotating spinosad with other pesticides lacking cross-resistance.
Asunto(s)
Aptitud Genética , Resistencia a los Insecticidas , Insecticidas/farmacología , Macrólidos/farmacología , Thysanoptera/efectos de los fármacos , Animales , Combinación de Medicamentos , Conducta Alimentaria/efectos de los fármacos , Femenino , Masculino , Ninfa/efectos de los fármacos , Ninfa/genética , Ninfa/crecimiento & desarrollo , Ninfa/fisiología , Pupa/efectos de los fármacos , Pupa/genética , Pupa/crecimiento & desarrollo , Pupa/fisiología , Thysanoptera/genética , Thysanoptera/crecimiento & desarrollo , Thysanoptera/fisiologíaRESUMEN
Tomato spotted wilt virus (TSWV) is transmitted by Frankliniella occidentalis (Pergande) in a persistent-propagative manner. We previously observed significant results in terms of feeding behavior of spinosad-susceptible (Ivf03) and -resistant (Spin-R) strains of F. occidentalis using electrical penetration graph. TSWV transmission by the two strains was compared in the present study. The results showed that the titer of TSWV-N RNA (a part of S RNA of TSWV and encoding the nucleocapsid protein) in Ivf03 and Spin-R strains was not significantly different after a 48-h inoculation access period. The TSWV transmission rate did not significantly differ between the two strains and was 51.0% for Ivf03 and 44.4% for Spin-R. The virus transmission rate was significantly higher for males than females of both strains. The virus transmission rate for males and females of Ivf03 was 68.1 and 33.8%, respectively; however, in case of Spin-R, it was 60 and 28.8% for males and females, respectively. Additionally, number of probes and duration of probes were generally greater for viruliferous females of Ivf03 than for viruliferous females of Spin-R but the total number and duration of noningestion probes did not significantly differ between males of the two strains. The latter finding behavior may help explain the similar transmission rates for the susceptible and resistant strains.