What if a plant doesn’t smell like a plant? Suppressing monoterpenes to enhance cotton pest resistance

The volatiles of plants play important roles in insect–plant interactions. On one hand, some volatile compounds help pests locate their host plants; on the other hand, some volatiles attract natural enemies to protect the plant. By understanding these interactions, we can develop new pest management strategies. Most previous studies have focused on how to attract more natural enemies by overexpressing volatiles, rather than investigating how reducing specific volatiles might help prevent pests from finding their host plant. In this study, we used Virus-Induced Gene Silencing (VIGS) to manipulate the expression of GhTPS3, which is an important gene involved in the biosynthesis of volatile monoterpenes such as α-pinene, β-pinene, β-phellandrene, and γ-terpinene in cotton (Gossypium hirsutum). In particular, α- and β-pinene are major volatiles emitted by cotton and used as cues by herbivores. VIGS treatment reduced the expression of GhTPS3 and the amounts of α- and β-pinene detected by GC-MS were significantly lower compared to GFP and negative control groups. In choice bioassays, we found that cotton aphids (Aphis gossypii) preferred cotton plants emitting α- and β-pinene compared to the GhTPS3 knockdown treatment, up to four weeks after infestation. These results highlight volatile manipulation as a potential pest management strategy in cotton. Future work will focus on other cotton pests and the impact on natural enemies.