Abstract
BackgroundPlant allelochemicals act as toxins, inhibitors of digestion, and deterrents that affect the fecundity of insects. These compounds have attracted significant research attention in recent decades, and much is known about the effects of these xenobiotic plant secondary metabolites on insect development. To date, although ecological interactions between xenobiotic plant secondary chemicals that retard insect growth have been observed in many species, it remains unclear how particular allelochemicals influence insect development in a life stage-dependent manner.ResultsWe found that 2-tridecanone can affect insect development; this effect appears similar to the symptoms induced by the physiological imbalance between juvenile and molting hormones in cotton bollworm. We later detected that a decrease in the concentration of 20-hydroxyecdysone occurred alongside the observed symptoms. We next identified the transcriptome of Helicoverpa armigera and eightdigital gene expression libraries for shading light on how 2-tridecanone retarded the development of cotton bollworm. The expression of CYP314A1, CYP315A1, CYP18A1, CYP307A1, and CYP306A1 (unigenes 16487, 15409, 40026, 41217, 35643, 16953, 8199, 13311, and 13036) were found to be induced by 2-tridecanone; these are known to be related to the biosynthesis or metabolism of 20-hydroxyecdysone. Expression analysis and RNA interference studies established that the retardant effect of 2-tridecanone on the development of cotton bollworm is mediated by P450 genes.ConclusionsThe candidate P450 gene approach described and exploited here is useful for identifying potential causal genes for the influence of plant allelochemicals on insect development.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3277-y) contains supplementary material, which is available to authorized users.
Highlights
Plant allelochemicals act as toxins, inhibitors of digestion, and deterrents that affect the fecundity of insects
Our experimental results showed that the plant allelochemical 2-TD affects insect development (Table 1), and we observed that a decrease in the concentration of 20E occurred along with the growth retardation symptoms following 2-TD treatment (Table 1). 2-TD treatment induced the expression of P450 detoxification enzyme genes
Other 2-TDregulated mito.CYP genes are related to the metabolism of molting hormone, but there have been no reports to prove that these two unigenes are involved in the biosynthesis or metabolism of molting hormone. Both the up- and down-regulation of these two P450 unigenes may be of critical importance in the development and metamorphosis of insects. As many of these genes are conserved among many insect species, our study provides a foundation for the functional characterization of the roles of these two P450 unigenes in insect development and metamorphosis
Summary
Plant allelochemicals act as toxins, inhibitors of digestion, and deterrents that affect the fecundity of insects. These compounds have attracted significant research attention in recent decades, and much is known about the effects of these xenobiotic plant secondary metabolites on insect development. Ecological interactions between xenobiotic plant secondary chemicals that retard insect growth have been observed in many species, it remains unclear how particular allelochemicals influence insect development in a life stage-dependent manner. Plant allelochemicals are known to induce the expression of various cytochrome P450 genes in insects. Many studies have demonstrated that the expression levels of cotton bollworm cytochrome P450 genes can be induced by plant allelochemicals [12,13,14]. The expression of CYP6AE, CYP9A, and CYP6B subfamily transcripts can be induced by xanthotoxin [16, 17]. 2-TD can significantly induce the expression of CYP6B6 [14]
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