Stability of Culex quinquefasciatus resistance to Bacillus sphaericus evaluated by molecular tools

Amorim, Liliane Barbosa; Barros, Rosineide Arruda de; Chalegre, Karlos Diogo de Melo; Oliveira, Cláudia Maria Fontes de; Regis, Lêda; Silva-Filha, Maria Helena Neves Lobo

doi:10.1016/j.ibmb.2010.02.002

Cited by 19 publications

(28 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From the evolutionary point of view, further studies are needed in order to clarify the mechanisms responsible for the rise of such events in this specific region of the cqm1 gene, as well as the impact of these alleles on the biological performance of the targeted insects. Although resistance in individuals from the CqRL1/2362 colony was related to a discrete reduction of some biological parameters (9), this colony has been maintained in the laboratory for more than 10 years and recent data have shown that the cqm1 REC allele is able to compete with cqm1, at least under laboratory conditions (1). Similarly, cadherin genes, in view of null alleles found associated with Cry1Ac resistance, do not seem to be essential for the survival of H. virescens, P. gossypiella, and H. armigera (12,22,45).…”

Section: Discussionmentioning

confidence: 99%

Novel Mutations Associated with Resistance to Bacillus sphaericus in a Polymorphic Region of the Culex quinquefasciatus cqm1 Gene

Chalegre

Romão

Tavares

et al. 2012

Appl Environ Microbiol

Self Cite

View full text Add to dashboard Cite

Bin toxin from Bacillus sphaericus acts on Culex quinquefasciatus larvae by binding to Cqm1 midgut-bound receptors, and disruption of the cqm1 gene is the major cause of resistance. The goal of this work was to screen for a laboratory-selected resistance cqm1 REC allele in field populations in the city of Recife, Brazil, and to describe other resistance-associated polymorphisms in the cqm1 gene. The cqm1 REC allele was detected in the four nontreated populations surveyed at frequencies from 0.001 to 0.017, and sequence analysis from these samples revealed a novel resistant allele (cqm1 REC-D16 ) displaying a 16-nucletotide (nt) deletion which is distinct from the 19-nt deletion associated with cqm1 REC . Yet a third resistant allele (cqm1 REC-D25 ), displaying a 25-nt deletion, was identified in samples from a treated area exposed to B. sphaericus. A comparison of the three deletion events revealed that all are located within the same 208-nt region amplified during the screening procedure. They also introduce equivalent frameshifts in the sequence and generate the same premature stop codon, leading to putative transcripts encoding truncated proteins which are unable to locate to the midgut epithelium. The populations analyzed in this study contained a variety of alleles with mutations disrupting the function of the corresponding Bin toxin receptor. Their locations reveal a hot spot that can be exploited to assess the resistance risk through DNA screening.T he utilization of biolarvicides based on Bacillus sphaericus requires monitoring strategies which can predict or prevent potential resistance selection among exposed mosquito populations. The binary (Bin) crystal toxin, which is the major active insecticidal factor found in commercial B. sphaericus strains, acts on mosquito larvae after ingestion, processing and binding to specific receptors located on the midgut epithelium (5, 24). Bin toxin displays high activity against larvae of the Culex pipiens complex and B. sphaericus has an excellent persistence under field conditions, which make this an effective biolarvicide for controlling these species in urban areas (17). However, the mode of action of Bin toxin relies entirely on its binding to a single class of midgut receptors which are glycosylphosphatidylinositol (GPI)-anchored ␣-glucosidases named Cpm1 and Cqm1 for Culex pipiens and Culex quinquefasciatus, respectively (7,29,30). Failure of toxins to bind to their midgut receptors has been described, in a wide range of target insects, as the primary resistance mechanism to insecticidal proteins from entomopathogenic bacteria (11,16,25). In the case of B. sphaericus, this is a critical aspect since resistance cases have also been reported after laboratory selection or field exposure (2,25,27,36,38,44).Investigation of the B. sphaericus resistance mechanisms has confirmed the essential role for the binding of Bin toxin to its receptors, since mutations within the cpm1/cqm1 genes, which are recessively inherited, are the major causes leading to the absence of ...

show abstract

Section: Discussionmentioning

confidence: 99%

Novel Mutations Associated with Resistance to Bacillus sphaericus in a Polymorphic Region of the Culex quinquefasciatus cqm1 Gene

Chalegre

Romão

Tavares

et al. 2012

Appl Environ Microbiol

Self Cite

View full text Add to dashboard Cite

show abstract

“…In mosquitoes, resistances to chemical insecticides were shown to increase development time or to reduce survival, fecundity, wing length or mating success (De Oliveira et al 2003;Bourguet et al 2004;Berticat et al 2008). The second method consists of monitoring the changes in resistance allele frequencies in space (through transects between resistant and susceptible populations, Lenormand et al 1999) or time (over several generations without pesticide, Gilliland et al 1998;Roux et al 2005a;Amorim et al 2010). The main advantage of this method is that it takes into account the fitness costs expressed at all the life-stages of the resistant phenotype (Gilliland et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Fitness costs of resistance to Bti toxins in the dengue vector Aedes aegypti

2011

View full text Add to dashboard Cite

Sustainable insect vector disease control strategies involve delaying the evolution of resistance to insecticides in natural populations. The evolutionary dynamics of resistance in the field is highly dependent on the fitness cost of resistance alleles. To successfully manage resistance evolution in target species, it is not only important to find evidence of fitness cost in resistant insects, but also to determine at which stage of the insect's life it is expressed. Here, we show that resistance costs to the bacterio-insecticide Bacillus thuringiensis subsp. israelensis (Bti) are expressed at all the life-stages of the dengue vector Aedes aegypti, including egg survival, larval development time, and female fecundity. We show that the storage of eggs for 4 months is long enough to counter-select resistance alleles. This suggests that Bti resistance is not likely to evolve in temperate climates where most mosquito species overwinter as eggs. In tropical regions with a rapid turn-over of generations, resistance alleles are likely to be counter-selected in only few generations without treatment through fitness costs expressed in terms of larval development time and female fecundity. We discuss the implications of our findings in terms of sustainable management strategies in light of the challenge of preserving the long-term efficiency of this environmentally safe anti-mosquito bio-insecticide.

show abstract

“…If mosquitoes develop resistance to one strain of Bs, it appears that they will develop resistance to other Bs strains due to the similarity of the binary toxins in most strains; but, they remain susceptible to Bti [176]. Resistant strain fitness was found to be heavily impacted, especially fecundity and fertility, which became very low in a study [204,205], although opposite results were achieved in another study [206].…”

Section: Resistance To Btimentioning

confidence: 98%

Mosquito-Borne Diseases Emergence/Resurgence and How to Effectively Control It Biologically

2020

View full text Add to dashboard Cite

Deadly pathogens and parasites are transmitted by vectors and the mosquito is considered the most threatening vector in public health, transmitting these pathogens to humans and animals. We are currently witnessing the emergence/resurgence in new regions/populations of the most important mosquito-borne diseases, such as arboviruses and malaria. This resurgence may be the consequence of numerous complex parameters, but the major cause remains the mismanagement of insecticide use and the emergence of resistance. Biological control programmes have rendered promising results but several highly effective techniques, such as genetic manipulation, remain insufficiently considered as a control mechanism. Currently, new strategies based on attractive toxic sugar baits and new agents, such as Wolbachia and Asaia, are being intensively studied for potential use as alternatives to chemicals. Research into new insecticides, Insect Growth Regulators, and repellent compounds is pressing, and the improvement of biological strategies may provide key solutions to prevent outbreaks, decrease the danger to at-risk populations, and mitigate resistance.Pathogens 2020, 9, 310 2 of 26 are not used at all, and those that are still in the test or design phase but are very promising, which we suggest to be considered in the biological control of mosquito-borne diseases.

show abstract

Stability of Culex quinquefasciatus resistance to Bacillus sphaericus evaluated by molecular tools

Cited by 19 publications

References 38 publications

Novel Mutations Associated with Resistance to Bacillus sphaericus in a Polymorphic Region of the Culex quinquefasciatus cqm1 Gene

Novel Mutations Associated with Resistance to Bacillus sphaericus in a Polymorphic Region of the Culex quinquefasciatus cqm1 Gene

Fitness costs of resistance to Bti toxins in the dengue vector Aedes aegypti

Mosquito-Borne Diseases Emergence/Resurgence and How to Effectively Control It Biologically

Contact Info

Product

Resources

About