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Genetic elimination of field-cage populations of Mediterranean fruit flies.

Leftwich PT, Koukidou M, Rempoulakis P, Gong HF, Zacharopoulou A, Fu G, Chapman T, Economopoulos A, Vontas J, Alphey L - Proc. Biol. Sci. (2014)

Bottom Line: Our results show (i) full functionality of RIDL, (ii) equivalency of RIDL and wild-type strains for life-history characteristics, and (iii) a high level of sexual competitiveness against both wild-type and wild-derived males.Weekly releases of OX3864A males into stable populations of wild-type medfly caused a successive decline in numbers, leading to eradication.The results show that genetic control can provide an effective alternative to SIT for the control of pest insects.

View Article: PubMed Central - PubMed

Affiliation: Oxitec Limited, 71 Innovation Drive, Milton Park, Oxford OX14 4RQ, UK School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk NR4 7TJ, UK.

ABSTRACT
The Mediterranean fruit fly (medfly, Ceratitis capitata Wiedemann) is a pest of over 300 fruits, vegetables and nuts. The sterile insect technique (SIT) is a control measure used to reduce the reproductive potential of populations through the mass release of sterilized male insects that mate with wild females. However, SIT flies can display poor field performance, due to the effects of mass-rearing and of the irradiation process used for sterilization. The development of female-lethal RIDL (release of insects carrying a dominant lethal) strains for medfly can overcome many of the problems of SIT associated with irradiation. Here, we present life-history characterizations for two medfly RIDL strains, OX3864A and OX3647Q. Our results show (i) full functionality of RIDL, (ii) equivalency of RIDL and wild-type strains for life-history characteristics, and (iii) a high level of sexual competitiveness against both wild-type and wild-derived males. We also present the first proof-of-principle experiment on the use of RIDL to eliminate medfly populations. Weekly releases of OX3864A males into stable populations of wild-type medfly caused a successive decline in numbers, leading to eradication. The results show that genetic control can provide an effective alternative to SIT for the control of pest insects.

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Life-history traits of fsRIDL strain flies, visualization of RIDL transformation marker and RIDL construct details. (a) Key elements of transgenic constructs: OX3864 and OX3647 use a tetO–tTA positive feedback system to give tetracycline-repressible lethality [26,31], rendered female-specific by addition of two sex-specific alternative splicing introns from two different tephritid species (to avoid repetitive genetic elements and the risk of recombination): Bactrocera zonata, BzTra (GenBank accession: BankIt1696174 BzTra KJ397268), and Ceratitis capitata, CcTra [28]. Only females produce splice variants encoding functional tTA protein. OX3864 and OX3647 differ in the promoter used for DsRed2. OX3864 used HR5 IE1, whereas OX3647 used polyubiquitin. (b) DsRed2 fluorescence renders the RIDL males (middle, OX3647Q; right, OX3864A) easily and reliably distinguishable from wt (left). (c) Same adults as in panel (b), under white light. (d) Survival under stress test conditions, i.e. without food or water post-eclosion. Adult male and female survival data are combined (n = 180). (e) Survival under non-stressed conditions of ad libitum food and water (n = 180), OX3647Q showed significantly reduced survival relative to wt. (f) Female lifetime egg productivity: average production from three cages of 30 females over three weeks. Wt lines produced more eggs than the other three lines; OX3864A produced more eggs than tsl and OX3647Q. (g) Individual female lifetime fecundity: no difference between the strains in the average number of eggs laid per female. (h) Hatching rates of eggs laid by the females in panel (g). tsl and OX3647Q had reduced egg hatch rates relative to wt, OX3864A did not differ from wt. All values are mean (±s.e.) unless otherwise stated.
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RSPB20141372F1: Life-history traits of fsRIDL strain flies, visualization of RIDL transformation marker and RIDL construct details. (a) Key elements of transgenic constructs: OX3864 and OX3647 use a tetO–tTA positive feedback system to give tetracycline-repressible lethality [26,31], rendered female-specific by addition of two sex-specific alternative splicing introns from two different tephritid species (to avoid repetitive genetic elements and the risk of recombination): Bactrocera zonata, BzTra (GenBank accession: BankIt1696174 BzTra KJ397268), and Ceratitis capitata, CcTra [28]. Only females produce splice variants encoding functional tTA protein. OX3864 and OX3647 differ in the promoter used for DsRed2. OX3864 used HR5 IE1, whereas OX3647 used polyubiquitin. (b) DsRed2 fluorescence renders the RIDL males (middle, OX3647Q; right, OX3864A) easily and reliably distinguishable from wt (left). (c) Same adults as in panel (b), under white light. (d) Survival under stress test conditions, i.e. without food or water post-eclosion. Adult male and female survival data are combined (n = 180). (e) Survival under non-stressed conditions of ad libitum food and water (n = 180), OX3647Q showed significantly reduced survival relative to wt. (f) Female lifetime egg productivity: average production from three cages of 30 females over three weeks. Wt lines produced more eggs than the other three lines; OX3864A produced more eggs than tsl and OX3647Q. (g) Individual female lifetime fecundity: no difference between the strains in the average number of eggs laid per female. (h) Hatching rates of eggs laid by the females in panel (g). tsl and OX3647Q had reduced egg hatch rates relative to wt, OX3864A did not differ from wt. All values are mean (±s.e.) unless otherwise stated.

Mentions: Repressible female-specific lethality was achieved by introduction of alternatively spliced, sex-specific introns from the medfly and the peach fruit fly transformer genes (Cctra and Bztra) in the tTA open reading frame [28]. Only females produce functional tTA, and this initiates a lethal tTA positive feedback loop in the absence of tetracycline (figure 1a) [28]. This mechanism functions as both the pre-release genetic sexing and post-release population suppression mechanism. The OX3864A and OX3647Q strains developed and tested here contained potentially significant improvements over previous fsRIDL strains. These include double tetO/tTA autoloops with two separate tra introns in the open reading frames, and DsRed2 fluorescent markers for ease of identification (figure 1b,c) [25,28]. tsl is the genetic sexing strain T(Y;5)101 called also Vienna-8 (without the pericentric inversion D53), introgressed into the TOLIMAN wt [35].Figure 1.


Genetic elimination of field-cage populations of Mediterranean fruit flies.

Leftwich PT, Koukidou M, Rempoulakis P, Gong HF, Zacharopoulou A, Fu G, Chapman T, Economopoulos A, Vontas J, Alphey L - Proc. Biol. Sci. (2014)

Life-history traits of fsRIDL strain flies, visualization of RIDL transformation marker and RIDL construct details. (a) Key elements of transgenic constructs: OX3864 and OX3647 use a tetO–tTA positive feedback system to give tetracycline-repressible lethality [26,31], rendered female-specific by addition of two sex-specific alternative splicing introns from two different tephritid species (to avoid repetitive genetic elements and the risk of recombination): Bactrocera zonata, BzTra (GenBank accession: BankIt1696174 BzTra KJ397268), and Ceratitis capitata, CcTra [28]. Only females produce splice variants encoding functional tTA protein. OX3864 and OX3647 differ in the promoter used for DsRed2. OX3864 used HR5 IE1, whereas OX3647 used polyubiquitin. (b) DsRed2 fluorescence renders the RIDL males (middle, OX3647Q; right, OX3864A) easily and reliably distinguishable from wt (left). (c) Same adults as in panel (b), under white light. (d) Survival under stress test conditions, i.e. without food or water post-eclosion. Adult male and female survival data are combined (n = 180). (e) Survival under non-stressed conditions of ad libitum food and water (n = 180), OX3647Q showed significantly reduced survival relative to wt. (f) Female lifetime egg productivity: average production from three cages of 30 females over three weeks. Wt lines produced more eggs than the other three lines; OX3864A produced more eggs than tsl and OX3647Q. (g) Individual female lifetime fecundity: no difference between the strains in the average number of eggs laid per female. (h) Hatching rates of eggs laid by the females in panel (g). tsl and OX3647Q had reduced egg hatch rates relative to wt, OX3864A did not differ from wt. All values are mean (±s.e.) unless otherwise stated.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150327&req=5

RSPB20141372F1: Life-history traits of fsRIDL strain flies, visualization of RIDL transformation marker and RIDL construct details. (a) Key elements of transgenic constructs: OX3864 and OX3647 use a tetO–tTA positive feedback system to give tetracycline-repressible lethality [26,31], rendered female-specific by addition of two sex-specific alternative splicing introns from two different tephritid species (to avoid repetitive genetic elements and the risk of recombination): Bactrocera zonata, BzTra (GenBank accession: BankIt1696174 BzTra KJ397268), and Ceratitis capitata, CcTra [28]. Only females produce splice variants encoding functional tTA protein. OX3864 and OX3647 differ in the promoter used for DsRed2. OX3864 used HR5 IE1, whereas OX3647 used polyubiquitin. (b) DsRed2 fluorescence renders the RIDL males (middle, OX3647Q; right, OX3864A) easily and reliably distinguishable from wt (left). (c) Same adults as in panel (b), under white light. (d) Survival under stress test conditions, i.e. without food or water post-eclosion. Adult male and female survival data are combined (n = 180). (e) Survival under non-stressed conditions of ad libitum food and water (n = 180), OX3647Q showed significantly reduced survival relative to wt. (f) Female lifetime egg productivity: average production from three cages of 30 females over three weeks. Wt lines produced more eggs than the other three lines; OX3864A produced more eggs than tsl and OX3647Q. (g) Individual female lifetime fecundity: no difference between the strains in the average number of eggs laid per female. (h) Hatching rates of eggs laid by the females in panel (g). tsl and OX3647Q had reduced egg hatch rates relative to wt, OX3864A did not differ from wt. All values are mean (±s.e.) unless otherwise stated.
Mentions: Repressible female-specific lethality was achieved by introduction of alternatively spliced, sex-specific introns from the medfly and the peach fruit fly transformer genes (Cctra and Bztra) in the tTA open reading frame [28]. Only females produce functional tTA, and this initiates a lethal tTA positive feedback loop in the absence of tetracycline (figure 1a) [28]. This mechanism functions as both the pre-release genetic sexing and post-release population suppression mechanism. The OX3864A and OX3647Q strains developed and tested here contained potentially significant improvements over previous fsRIDL strains. These include double tetO/tTA autoloops with two separate tra introns in the open reading frames, and DsRed2 fluorescent markers for ease of identification (figure 1b,c) [25,28]. tsl is the genetic sexing strain T(Y;5)101 called also Vienna-8 (without the pericentric inversion D53), introgressed into the TOLIMAN wt [35].Figure 1.

Bottom Line: Our results show (i) full functionality of RIDL, (ii) equivalency of RIDL and wild-type strains for life-history characteristics, and (iii) a high level of sexual competitiveness against both wild-type and wild-derived males.Weekly releases of OX3864A males into stable populations of wild-type medfly caused a successive decline in numbers, leading to eradication.The results show that genetic control can provide an effective alternative to SIT for the control of pest insects.

View Article: PubMed Central - PubMed

Affiliation: Oxitec Limited, 71 Innovation Drive, Milton Park, Oxford OX14 4RQ, UK School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk NR4 7TJ, UK.

ABSTRACT
The Mediterranean fruit fly (medfly, Ceratitis capitata Wiedemann) is a pest of over 300 fruits, vegetables and nuts. The sterile insect technique (SIT) is a control measure used to reduce the reproductive potential of populations through the mass release of sterilized male insects that mate with wild females. However, SIT flies can display poor field performance, due to the effects of mass-rearing and of the irradiation process used for sterilization. The development of female-lethal RIDL (release of insects carrying a dominant lethal) strains for medfly can overcome many of the problems of SIT associated with irradiation. Here, we present life-history characterizations for two medfly RIDL strains, OX3864A and OX3647Q. Our results show (i) full functionality of RIDL, (ii) equivalency of RIDL and wild-type strains for life-history characteristics, and (iii) a high level of sexual competitiveness against both wild-type and wild-derived males. We also present the first proof-of-principle experiment on the use of RIDL to eliminate medfly populations. Weekly releases of OX3864A males into stable populations of wild-type medfly caused a successive decline in numbers, leading to eradication. The results show that genetic control can provide an effective alternative to SIT for the control of pest insects.

Show MeSH
Related in: MedlinePlus