Abstract
Plant varieties expressing the Bt (Bacillus thuringiensis) insecticidal proteins Cry1Ah and Cry2Ab have potential commercialization prospects in China. However, their potential effects on non-target arthropods (NTAs) remain uncharacterized. The cotton aphid Aphis gossypii is a worldwide pest that damages various important crops. The ladybeetle Propylea japonica is a common and abundant natural enemy in many cropping systems in East Asia. In the present study, the effects of Cry1Ah and Cry2Ab proteins on A. gossypii and P. japonica were assessed from three aspects. First, neither of the Cry proteins affected the growth or developmental characteristics of the two test insects. Second, the expression levels of the detoxification-related genes of the two test insects did not change significantly in either Cry protein treatment. Third, neither of the Cry proteins had a favourable effect on the expression of genes associated with the amino acid metabolism of A. gossypii and the nutrition utilization of P. japonica. In conclusion, the Cry1Ah and Cry2Ab proteins do not appear to affect the cotton aphid A. gossypii or the ladybeetle P. japonica.
Highlights
Toxin (Cry1Ac) is grown in China, the world’s leading producer of cotton[9]
We investigated the effects of Cry1Ah and Cry2Ab proteins on cotton aphid A. gossypii and ladybeetle P. japonica from three aspects: (1) the toxicity of Cry proteins on the growth and developmental characteristics of A. gossypii and P. japonica; (2) the detoxification response of A. gossypii and P. japonica to Cry proteins; and (3) the effects of Cry proteins on the expression of genes that are associated with the amino acid metabolism of A. gossypii and the nutrition utilization of P. japonica
In the Cry1Ah treatment, genes that are associated with A. gossypii detoxification responses [i.e., CYP6A2, CYP6A13, glutathione S-transferase delta 1 (GSTd1), carboxylesterases (CarE)] were slightly up-regulated compared with the control treatment, whereas only the gene CYP6A14 was slightly down-regulated (Fig. 1)
Summary
Toxin (Cry1Ac) is grown in China, the world’s leading producer of cotton[9]. To cope with pest resistance, a new cotton cultivar (producing Cry1Ac and Cry2Ab) has been developed in China and will be commercially available in the foreseeable future[10,11]. Throughout East Asia, the ladybird beetle Propylea japonica (Thunberg) (Coleoptera: Coccinellidae) is a common and abundant natural enemy in many cropping systems, including maize, cotton, rice, vegetables, and fruit trees[21,22,23] Both the larvae and adults feed on aphids, thrips, spider mites, and the eggs and young larvae of Lepidoptera[24]. The quantitative nutritional approach consists of measuring the amount of food that is consumed, digested and assimilated, excreted, metabolized, and converted into biomass[36] An analysis of these measurements reveals how organisms respond to different foods and which food components exert the greatest effects on growth[37]. This method has been used to investigate how Bt proteins influence insects[38,39,40]
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