Picture of an aphid sitting on a leaf. Image credit: Viktor Forgacs (CC0)
The peach aphid is one of the most harmful pests worldwide and can parasitize over 400 species of plants. In addition to sucking phloem sap and secreting honeydew, the peach aphid can also spread various plant viruses, causing severe crop yield reductions and huge economic losses.
So far, the control of peach aphids mainly relies on chemical pesticides. However, the long-term and unreasonable use of these chemicals has led to environmental pollution and prompted aphids to develop resistance to pesticides, making the control of these insects even more difficult. Therefore, it is imperative to develop new, environmentally friendly insecticides.
For example, secondary plant metabolites, such as betulin – which is a key bioactive compound in aphid-resistant wild peach – have been proven to be highly toxic to aphids, demonstrating significant potential for development as a green insecticide. To find out how exactly betulin acts against aphids, Wang et al. used a combination of field trials and molecular, genetic and electrophysiological approaches.
The results showed that betulin inhibits the expression of MpGABR – a gene that helps regulate nerve signals in aphids – while simultaneously suppressing the function of the MpGABR protein by binding to its specific structural component called THR228. Exposing aphids to betulin significantly inhibited the expression of MpGABR. Micro-scale thermophoresis (a technique used to measure the binding between molecules) and voltage clamp experiments (used to study how compounds affect ion channel activity) confirmed that betulin could bind to the MpGABR protein via THR228 and acted as its inhibitor. Molecular docking (a computer method that predicts how a molecule interacts with a protein), mutagenesis analysis, and genome editing studies further suggested that THR228 is a key site that has remained nearly unchanged in aphid through evolution because it is essential for the protein’s function.
The findings of Wang et al. will be beneficial for pesticide companies for developing new products, helping farmers control aphids and avoiding environmental pollution. More research is needed before these benefits can be realized, such as solvent formulation trials for developing betulin as an aphid insecticide, regional trials for using betulin as an aphid insecticide, and screening for insecticides with similar functions to this metabolite.
