A Salivary Effector of the Pea Aphid Interacts with Pea Proteins and Enhances Its Performance on the Host Plant.

Aphids have intricate interactions with their host plants, but the molecular mechanisms behind these interactions remain largely unknown. The pea aphid, Acyrthosiphon pisum, is a legume specialist that forms a complex of several biotypes, each specialized in feeding on a few legume species. Aphids inject a cocktail of salivary effector proteins into plants to suppress plant immunity and promote their performance, such as fecundity. Previous studies showed that subsets of salivary effector genes of A. pisum are differentially expressed between the pea- and alfalfa-adapted biotypes. We hypothesized that the salivary effector genes that are important for A. pisum to feed on pea (Pisum sativum) are highly expressed in the pea-adapted biotype compared with non-adapted ones and selected such genes for functional characterization. We examined 10 candidate genes and found that expression of the salivary gene LOC100159932 (Ap4) in pea leaves increased the fecundity of the A. pisum pea biotype. A yeast two-hybrid screening using Ap4 as a bait identified two pea proteins named PsBPL1 and PsBPL2 that showed high homology with Arabidopsis BPL (Binding Partner of ACD11-Like) proteins, which are conserved in plants and fungi and known to be involved in plant immunity. GFP-tagged Ap4 proteins produced puncta in Nicotiana benthamiana cytoplasm, and a bimolecular fluorescence complementation experiment confirmed the interaction of Ap4 and PsBPL1 and PSBPL2 in planta. These results highlight Ap4's role as an effector and suggest the involvement of BPL proteins in pea-aphid interactions. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.