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Conditional embryonic lethality to improve the sterile insect technique in Ceratitis capitata (Diptera: Tephritidae).

Schetelig MF, Caceres C, Zacharopoulou A, Franz G, Wimmer EA - BMC Biol. (2009)

Bottom Line: These elements act differently in expression strength and their ability to drive lethal effector gene activation.Moreover, position effects strongly influence the efficiency of the system.Out of 60 combinations of driver and effector construct integrations, several lines resulted in larval and pupal lethality with one line showing complete embryonic lethality.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Developmental Biology, Göttingen Center for Molecular Biosciences, Johann-Friedrich-Blumenbach-Institute of Zoology and Anthropology, Georg-August-University Göttingen, GZMB, Ernst-Caspari-Haus, Göttingen, Germany. marc.schetelig@ars.usda.gov

ABSTRACT

Background: The sterile insect technique (SIT) is an environment-friendly method used in area-wide pest management of the Mediterranean fruit fly Ceratitis capitata (Wiedemann; Diptera: Tephritidae). Ionizing radiation used to generate reproductive sterility in the mass-reared populations before release leads to reduction of competitiveness.

Results: Here, we present a first alternative reproductive sterility system for medfly based on transgenic embryonic lethality. This system is dependent on newly isolated medfly promoter/enhancer elements of cellularization-specifically-expressed genes. These elements act differently in expression strength and their ability to drive lethal effector gene activation. Moreover, position effects strongly influence the efficiency of the system. Out of 60 combinations of driver and effector construct integrations, several lines resulted in larval and pupal lethality with one line showing complete embryonic lethality. This line was highly competitive to wildtype medfly in laboratory and field cage tests.

Conclusion: The high competitiveness of the transgenic lines and the achieved 100% embryonic lethality causing reproductive sterility without the need of irradiation can improve the efficacy of operational medfly SIT programs.

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Mating competitiveness of LL #67 in field cage tests. To test the competitiveness of the embryonic LL #67, 20 non-irradiated and 20 irradiated males from LL #67 (120 Gy) competed with 20 non-irradiated wildtype (WT) Argentinean (Arg) males for mating with 20 WT Arg females in a field cage [17]. The males were marked with different colored water-based paints. Mating couples were taken out of the cage and the type of mating couple was recorded. Twelve replications were carried out. (A) The proportion of matings of each mating type was calculated by dividing the number of the occurred matings by the number of total possible matings (limited by the number of Arg females, n = 20). The proportion of matings was 18 ± 11% for non-irradiated LL #67 males, 13 ± 9% for irradiated LL #67 males, and 12 ± 12% for non-irradiated Arg males. The proportion of total matings over all 12 replications was 43 ± 5%, indicating an acceptable degree of sexual activity during the test period. Running a conventional ANOVA, no statistical differences (F = 1.62; P = 0.171) can be found between the different matings that occurred. The tests thus showed that non-irradiated and irradiated LL #67 males were at least as, if not more, competitive as WT non-irradiated Arg males. (B) Eggs and hatched larvae from each mating type were recorded and the egg hatch is shown. All matings of LL #67 males (regardless of whether non-irradiated or irradiated) to WT Arg females led to complete embryonic lethality. In comparison with the complete lethality of LL #67 (descending from EgII) with or without irradiation, previous sterility tests with irradiated WT EgII males (100 Gy) showed an egg hatch of 1.2% [35]. In addition, radiation-induced sterility has been shown to be indirectly correlated to the competitiveness of the flies [4].
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Figure 7: Mating competitiveness of LL #67 in field cage tests. To test the competitiveness of the embryonic LL #67, 20 non-irradiated and 20 irradiated males from LL #67 (120 Gy) competed with 20 non-irradiated wildtype (WT) Argentinean (Arg) males for mating with 20 WT Arg females in a field cage [17]. The males were marked with different colored water-based paints. Mating couples were taken out of the cage and the type of mating couple was recorded. Twelve replications were carried out. (A) The proportion of matings of each mating type was calculated by dividing the number of the occurred matings by the number of total possible matings (limited by the number of Arg females, n = 20). The proportion of matings was 18 ± 11% for non-irradiated LL #67 males, 13 ± 9% for irradiated LL #67 males, and 12 ± 12% for non-irradiated Arg males. The proportion of total matings over all 12 replications was 43 ± 5%, indicating an acceptable degree of sexual activity during the test period. Running a conventional ANOVA, no statistical differences (F = 1.62; P = 0.171) can be found between the different matings that occurred. The tests thus showed that non-irradiated and irradiated LL #67 males were at least as, if not more, competitive as WT non-irradiated Arg males. (B) Eggs and hatched larvae from each mating type were recorded and the egg hatch is shown. All matings of LL #67 males (regardless of whether non-irradiated or irradiated) to WT Arg females led to complete embryonic lethality. In comparison with the complete lethality of LL #67 (descending from EgII) with or without irradiation, previous sterility tests with irradiated WT EgII males (100 Gy) showed an egg hatch of 1.2% [35]. In addition, radiation-induced sterility has been shown to be indirectly correlated to the competitiveness of the flies [4].

Mentions: An ideal line for releasing purposes should be embryonic lethal, but should also be competitive. We therefore did competition tests with LLs #66 and #67 (Figure 6C). WT females were crossed with WT males and transgenic males in different ratios (1:1:1, 1:1:3, 1:1:5, and 1:1:9; these numbers represent the ratio of WT females: WT males: transgenic males). The reduction of progeny compared with WT-only controls showed that both lines are highly competitive. Remarkable is the higher fertilization success of LL #67 males compared with WT males starting from ratio 1:1:5. For the ratio 1:1:9 an overall progeny rate of only 0.4% was measured. At the same time a WT control at ratio 1:10:0 gave only little reduction of overall progeny (Figure 6C). Thus, transgenic males from LLs #66 and #67 performed in laboratory competition tests comparably or even better than WT males. Progeny from all competition tests were identified as non-transgenic individuals by fluorescent microscopy, which additionally indicated the complete lethality of LLs #66 and #67. Interestingly, all lines deriving from the effector line TREhs43-hidAla5_F1m2 (#66, #67, and #68) partially lacked anterior orbital bristles, which did not obviously interfere with the mating success of these transgenic males. In addition to laboratory tests, field cage tests [17] with LL #67 males showed a comparable or even better competitiveness than WT (Figure 7).


Conditional embryonic lethality to improve the sterile insect technique in Ceratitis capitata (Diptera: Tephritidae).

Schetelig MF, Caceres C, Zacharopoulou A, Franz G, Wimmer EA - BMC Biol. (2009)

Mating competitiveness of LL #67 in field cage tests. To test the competitiveness of the embryonic LL #67, 20 non-irradiated and 20 irradiated males from LL #67 (120 Gy) competed with 20 non-irradiated wildtype (WT) Argentinean (Arg) males for mating with 20 WT Arg females in a field cage [17]. The males were marked with different colored water-based paints. Mating couples were taken out of the cage and the type of mating couple was recorded. Twelve replications were carried out. (A) The proportion of matings of each mating type was calculated by dividing the number of the occurred matings by the number of total possible matings (limited by the number of Arg females, n = 20). The proportion of matings was 18 ± 11% for non-irradiated LL #67 males, 13 ± 9% for irradiated LL #67 males, and 12 ± 12% for non-irradiated Arg males. The proportion of total matings over all 12 replications was 43 ± 5%, indicating an acceptable degree of sexual activity during the test period. Running a conventional ANOVA, no statistical differences (F = 1.62; P = 0.171) can be found between the different matings that occurred. The tests thus showed that non-irradiated and irradiated LL #67 males were at least as, if not more, competitive as WT non-irradiated Arg males. (B) Eggs and hatched larvae from each mating type were recorded and the egg hatch is shown. All matings of LL #67 males (regardless of whether non-irradiated or irradiated) to WT Arg females led to complete embryonic lethality. In comparison with the complete lethality of LL #67 (descending from EgII) with or without irradiation, previous sterility tests with irradiated WT EgII males (100 Gy) showed an egg hatch of 1.2% [35]. In addition, radiation-induced sterility has been shown to be indirectly correlated to the competitiveness of the flies [4].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2662800&req=5

Figure 7: Mating competitiveness of LL #67 in field cage tests. To test the competitiveness of the embryonic LL #67, 20 non-irradiated and 20 irradiated males from LL #67 (120 Gy) competed with 20 non-irradiated wildtype (WT) Argentinean (Arg) males for mating with 20 WT Arg females in a field cage [17]. The males were marked with different colored water-based paints. Mating couples were taken out of the cage and the type of mating couple was recorded. Twelve replications were carried out. (A) The proportion of matings of each mating type was calculated by dividing the number of the occurred matings by the number of total possible matings (limited by the number of Arg females, n = 20). The proportion of matings was 18 ± 11% for non-irradiated LL #67 males, 13 ± 9% for irradiated LL #67 males, and 12 ± 12% for non-irradiated Arg males. The proportion of total matings over all 12 replications was 43 ± 5%, indicating an acceptable degree of sexual activity during the test period. Running a conventional ANOVA, no statistical differences (F = 1.62; P = 0.171) can be found between the different matings that occurred. The tests thus showed that non-irradiated and irradiated LL #67 males were at least as, if not more, competitive as WT non-irradiated Arg males. (B) Eggs and hatched larvae from each mating type were recorded and the egg hatch is shown. All matings of LL #67 males (regardless of whether non-irradiated or irradiated) to WT Arg females led to complete embryonic lethality. In comparison with the complete lethality of LL #67 (descending from EgII) with or without irradiation, previous sterility tests with irradiated WT EgII males (100 Gy) showed an egg hatch of 1.2% [35]. In addition, radiation-induced sterility has been shown to be indirectly correlated to the competitiveness of the flies [4].
Mentions: An ideal line for releasing purposes should be embryonic lethal, but should also be competitive. We therefore did competition tests with LLs #66 and #67 (Figure 6C). WT females were crossed with WT males and transgenic males in different ratios (1:1:1, 1:1:3, 1:1:5, and 1:1:9; these numbers represent the ratio of WT females: WT males: transgenic males). The reduction of progeny compared with WT-only controls showed that both lines are highly competitive. Remarkable is the higher fertilization success of LL #67 males compared with WT males starting from ratio 1:1:5. For the ratio 1:1:9 an overall progeny rate of only 0.4% was measured. At the same time a WT control at ratio 1:10:0 gave only little reduction of overall progeny (Figure 6C). Thus, transgenic males from LLs #66 and #67 performed in laboratory competition tests comparably or even better than WT males. Progeny from all competition tests were identified as non-transgenic individuals by fluorescent microscopy, which additionally indicated the complete lethality of LLs #66 and #67. Interestingly, all lines deriving from the effector line TREhs43-hidAla5_F1m2 (#66, #67, and #68) partially lacked anterior orbital bristles, which did not obviously interfere with the mating success of these transgenic males. In addition to laboratory tests, field cage tests [17] with LL #67 males showed a comparable or even better competitiveness than WT (Figure 7).

Bottom Line: These elements act differently in expression strength and their ability to drive lethal effector gene activation.Moreover, position effects strongly influence the efficiency of the system.Out of 60 combinations of driver and effector construct integrations, several lines resulted in larval and pupal lethality with one line showing complete embryonic lethality.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Developmental Biology, Göttingen Center for Molecular Biosciences, Johann-Friedrich-Blumenbach-Institute of Zoology and Anthropology, Georg-August-University Göttingen, GZMB, Ernst-Caspari-Haus, Göttingen, Germany. marc.schetelig@ars.usda.gov

ABSTRACT

Background: The sterile insect technique (SIT) is an environment-friendly method used in area-wide pest management of the Mediterranean fruit fly Ceratitis capitata (Wiedemann; Diptera: Tephritidae). Ionizing radiation used to generate reproductive sterility in the mass-reared populations before release leads to reduction of competitiveness.

Results: Here, we present a first alternative reproductive sterility system for medfly based on transgenic embryonic lethality. This system is dependent on newly isolated medfly promoter/enhancer elements of cellularization-specifically-expressed genes. These elements act differently in expression strength and their ability to drive lethal effector gene activation. Moreover, position effects strongly influence the efficiency of the system. Out of 60 combinations of driver and effector construct integrations, several lines resulted in larval and pupal lethality with one line showing complete embryonic lethality. This line was highly competitive to wildtype medfly in laboratory and field cage tests.

Conclusion: The high competitiveness of the transgenic lines and the achieved 100% embryonic lethality causing reproductive sterility without the need of irradiation can improve the efficacy of operational medfly SIT programs.

Show MeSH
Related in: MedlinePlus