Chemical inhibition of Kir channels reduces salivary secretions and phloem feeding of the cotton aphid, Aphis gossypii (Glover)

BACKGROUND The unique feeding biology of aphids suggests novel insecticide targets are likely to exist outside of the nervous system. We therefore aimed to directly test the hypothesis that pharmacological inhibition of inward rectifier potassium (Kir) channels would result in salivary gland failure and reduced sap ingestion by the cotton aphid, Aphis gossypii. RESULTS The Kir inhibitors VU041 and VU590 reduced the length of the salivary sheath in a concentration dependent manner, indicating that the secretory activity of the salivary gland is reduced by Kir inhibition. Next, we employed the electrical penetration graph (EPG) technique to measure the impact Kir inhibition has to aphid sap feeding and feeding biology. Data show that foliar application of VU041 eliminated the E1 and E2 phases (phloem feeding) in all aphids studied. Contact exposure to VU041 after foliar applications was found to be toxic to A. gossypii at 72 and 96 h post-infestation, indicating mortality is likely a result of starvation and not acute toxicity. Furthermore, VU041 exposure significantly altered the feeding behavior of aphids, which is toxicologically relevant for plant-virus interactions. CONCLUSION These data suggest Kir channels are critical for proper function of aphid salivary glands and the reduced plant feeding justifies future work in developing salivary gland Kir channels as novel mechanism aphicides. Furthermore, products like VU041 would add to a very minor arsenal of compounds that simultaneously reduce vector abundance and alter feeding behavior. (c) 2019 Society of Chemical Industry