Gene expression of pea aphid (Hemiptera: Aphididae) salivary effectors changes based on feeding duration and plant species.

Aphids are agricultural pests that damage crops directly through feeding and indirectly by transmitting plant viruses. Central to their success are salivary effectors, secreted proteins that suppress plant defenses and facilitate nutrient uptake. Nonetheless, numerous salivary effectors remain uncharacterized to date. It is unclear whether effector gene expression patterns vary in response to factors such as feeding duration, aphid age, tissue type, and host plant. To address current knowledge gaps, we reared pea aphids, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), and 2 host plants, barrel medic (Medicago truncatula Gaertn.) and broad bean (Vicia faba Linnaeus), under a controlled environment. Next, we quantified the gene expression patterns of 2 well-characterized (C002 and Armet) and 2 less studied aphid salivary effectors (Apolipophorin and ACYPI006346). The results show that salivary effector gene expression declines by 72 h when switching hosts (V. faba to M. truncatula), although some effectors display fluctuating patterns between specific time points (24 vs 48 h and 48 vs 72 h) when switching hosts (V. faba to M. truncatula) or not (M. truncatula to M. truncatula). One-day-old aphids consistently exhibit higher gene expression levels than older individuals when fed on a single host (V. faba to V. faba). These findings highlight the importance of considering temporal dynamics, developmental stage, and host context in studies of aphid effector biology. Our findings lay a methodological foundation that supports the design of more consistent and informative transcriptomic experiments on aphid-plant interactions.