TY - JOUR
T1 - Cadherin gene expression and effects of Bt resistance on sperm transfer in pink bollworm
AU - Carrière, Yves
AU - Showalter, Ann M.
AU - Fabrick, Jeff A.
AU - Sollome, James
AU - Ellers-Kirk, Christa
AU - Tabashnik, Bruce E.
N1 - Funding Information:
This research was partly supported by USDA Agriculture Biotechnology Risk Assessment Research Grant 2003-04371 and USDA National Research Initiative Grant 2006-35302-17365 . Mention of a commercial or proprietary product does not constitute a recommendation by the USDA. We thank Dawn Higginson and two anonymous reviewers for comments that improved the manuscript.
PY - 2009/11
Y1 - 2009/11
N2 - Cadherin proteins bind Bacillus thuringiensis (Bt) toxins in lepidopteran midguts but their inherent function remains unclear. In pink bollworm, Pectinophora gossypiella, three recessive mutations in a cadherin gene (BtR) are tightly linked with resistance to Bt toxin Cry1Ac. Here we examined patterns of transcription of this gene and the association between cadherin genotype and sperm transfer in pink bollworm. Cadherin RNA was most abundant in larvae, but was also found in adults and embryos. In fourth instar larvae, cadherin RNA was most abundant in the gut, yet its presence in the testes indicates a potential role in sperm production. Previously, we found reduced first-male paternity in pink bollworm males homozygous for cadherin mutations conferring resistance to Bt, when a resistant and susceptible male competed for access to a female. However, the number of offspring sired by resistant and susceptible males was similar without competition. Male Lepidoptera produce both fertile eupyrene sperm and anucleate, non-fertile apyrene sperm, suggesting that apyrene sperm may contribute to male reproductive success when sperm competition occurs. Accordingly, we hypothesized that cadherin-based resistance to Bt entails fitness costs that reduce apyrene sperm transfer. To test this hypothesis, we compared apyrene and eupyrene sperm transfer in males from four strains of pink bollworm. Transfer of apyrene and eupyrene sperm was lower in homozygous resistant than in susceptible males. Furthermore, homozygous resistant males weighed less than susceptible males, which could have diminished sperm transfer by resistant males directly, or via a positive association between male weight, spermatophore weight and sperm transfer. While data suggest that cadherin mutations induced a recessive fitness cost affecting apyrene sperm transfer, these mutations also generated recessive costs that affected other traits and could have lowered first-male paternity.
AB - Cadherin proteins bind Bacillus thuringiensis (Bt) toxins in lepidopteran midguts but their inherent function remains unclear. In pink bollworm, Pectinophora gossypiella, three recessive mutations in a cadherin gene (BtR) are tightly linked with resistance to Bt toxin Cry1Ac. Here we examined patterns of transcription of this gene and the association between cadherin genotype and sperm transfer in pink bollworm. Cadherin RNA was most abundant in larvae, but was also found in adults and embryos. In fourth instar larvae, cadherin RNA was most abundant in the gut, yet its presence in the testes indicates a potential role in sperm production. Previously, we found reduced first-male paternity in pink bollworm males homozygous for cadherin mutations conferring resistance to Bt, when a resistant and susceptible male competed for access to a female. However, the number of offspring sired by resistant and susceptible males was similar without competition. Male Lepidoptera produce both fertile eupyrene sperm and anucleate, non-fertile apyrene sperm, suggesting that apyrene sperm may contribute to male reproductive success when sperm competition occurs. Accordingly, we hypothesized that cadherin-based resistance to Bt entails fitness costs that reduce apyrene sperm transfer. To test this hypothesis, we compared apyrene and eupyrene sperm transfer in males from four strains of pink bollworm. Transfer of apyrene and eupyrene sperm was lower in homozygous resistant than in susceptible males. Furthermore, homozygous resistant males weighed less than susceptible males, which could have diminished sperm transfer by resistant males directly, or via a positive association between male weight, spermatophore weight and sperm transfer. While data suggest that cadherin mutations induced a recessive fitness cost affecting apyrene sperm transfer, these mutations also generated recessive costs that affected other traits and could have lowered first-male paternity.
KW - Bacillus thuringiensis
KW - Bt resistance
KW - Cadherin
KW - Fitness costs
KW - Pectinophora gossypiella
KW - Sperm competition
KW - Sperm transfer
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U2 - 10.1016/j.jinsphys.2009.07.013
DO - 10.1016/j.jinsphys.2009.07.013
M3 - Article
C2 - 19666026
AN - SCOPUS:70249083388
SN - 0022-1910
VL - 55
SP - 1058
EP - 1064
JO - Journal of Insect Physiology
JF - Journal of Insect Physiology
IS - 11
ER -