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Consumption of Bt rice pollen containing Cry1C or Cry2A does not pose a risk to Propylea japonica (Thunberg) (Coleoptera: Coccinellidae).

ABSTRACT: As a pollen feeder, Propylea japonica would be directly exposed to Cry proteins in Bacillus thuringiensis (Bt)-transgenic rice fields. The effect of Cry1C- or Cry2A-containing transgenic rice pollen on the fitness of P. japonica was assessed using two dietary-exposure experiments in the laboratory. In the first experiment, larval developmental time of P. japonica was significantly longer when fed pollen from Bt rice lines rather than control pollen but other life table parameters were not significantly affected. In the second experiment, P. japonica was not affected when fed a rapeseed pollen-based diet containing purified Cry1C or Cry2A at concentrations that were >10-times higher than in pollen, but P. japonica was affected when the diet contained E-64 as a positive control. In both experiments, the stability and bioactivity of the Cry proteins in the food sources and the uptake of the proteins by P. japonica were confirmed. The results show that P. japonica is not sensitive to Cry1C or Cry2A proteins; the effect observed in the first experiment was likely attributable to unknown differences in the nutritional composition of Bt rice pollen. Overall, the data indicate that the growing of Cry1C- or Cry2A-transgenic rice should pose a negligible risk to P. japonica.

SUBMITTER: Li Y

PROVIDER: S-EPMC4286735 | biostudies-other | 2015

REPOSITORIES: biostudies-other

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Project description:BackgroundEndosymbionts that manipulate the reproduction of their hosts have been reported widely in invertebrates. One such group of endosymbionts is the male-killers. To date all male-killers reported are bacterial in nature, but comprise a diverse group. Ladybirds have been described as a model system for the study of male-killing, which has been reported in multiple species from widespread geographic locations. Whilst criteria of low egg hatch-rate and female-biased progenic sex ratio have been used to identify female hosts of male-killers, variation in vertical transmission efficiency and host genetic factors may result in variation in these phenotypic indicators of male-killer presence. Molecular identification of bacteria and screening for bacterial presence provide us with a more accurate method than breeding data alone to link the presence of the bacteria to the male-killing phenotype. In addition, by identifying the bacteria responsible we may find evidence for horizontal transfer between endosymbiont hosts and can gain insight into the evolutionary origins of male-killing. Phylogenetic placement of male-killing bacteria will allow us to address the question of whether male-killing is a potential strategy for only some, or all, maternally inherited bacteria. Together, phenotypic and molecular characterisation of male-killers will allow a deeper insight into the interactions between host and endosymbiont, which ultimately may lead to an understanding of how male-killers identify and kill male-hosts.ResultsA male-killer was detected in the Japanese coccinellid, Propylea japonica (Thunberg) a species not previously known to harbour male-killers. Families produced by female P. japonica showed significantly female-biased sex ratios. One female produced only daughters. This male-killer trait was maternally inherited and antibiotic treatment produced a full, heritable cure. Molecular analysis identified Rickettsia to be associated with the trait in this species of ladybird.ConclusionWe conclude that P. japonica is host to a bacterial male-killer that is vertically inherited with variable transmission efficiency. Rickettsia presence correlates with the male-killing trait, but there is some variation in the phenotypic expression of the trait due to interaction with host factors. Phylogenetic analysis using the 16S rRNA and 17 kDa antigen genes suggests there may have been horizontal transfer of Rickettsial male-killers between different ladybird hosts.

Project description:As larval cannibalism is common under intensive rearing conditions, leg regeneration can help ladybugs adapt to the competitive environment, but whether the leg regeneration leads to side effects on development remains unclear. To analyze the potentially developmental cost of leg regeneration, the developmental period and weight of leg-regenerated Coccinella septempunctata were studied in the laboratory. The results showed that, when the time intervals between the emergency of 4th-instar larva and leg amputation increased, the developmental period of leg-regenerated 4th-instar larvae was gradually prolonged. Significantly developmental delay were also examined at prepupal and pupal stages, and various timings of leg amputation affected the periods of leg-regenerated prepupae/pupae similarly. After the leg was amputated at different larval instars, the developmental delay only occurred at the larval instar when the leg was amputated, whereas other larval instars failed to be extended, and the developmental periods of leg-regenerated prepupae/pupae were affected similarly by the instars of leg amputation. Developmental delays possibly resulted in more consumption by leg-regenerated larvae, and then weight gains at prepupal/pupal stages, but different larval instars of leg amputation affected the weight gain similarly. Both the developmental delay (at 4th-instar larval, prepupal and pupal stages) and weight gain (at pupal and adult stages) in complete/bilateral amputation were longer or greater than those in half/unilateral amputation. However, the thoracic locations of leg amputation impacted the developmental delay and weight gain similarly. Our study indicates that although leg regeneration triggers the developmental cost decreasing the competitive superiority or agility, C. septempunctata larvae still choose to completely regenerate the leg to adapt to complex environments. Thus, in order to remain competitive at adult stages, leg-impaired larvae may make an investment tradeoff between leg regeneration and developmental cost.

Dataset Information

Consumption of Bt rice pollen containing Cry1C or Cry2A does not pose a risk to Propylea japonica (Thunberg) (Coleoptera: Coccinellidae).

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