A novel chitinase-like family of candidate effectors unique to aphids
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Molecular interactions between aphids and plants include delivery of salivary effector proteins into host cells, acting as virulence factors to suppress host immunity, or as avirulence functions triggering immune activation. However, understanding of virulence and avirulence mechanisms in aphid-plant systems is currently limited. Here, we report discovery of an effector candidate family that is unique to aphids. Using functional genomics data on divergent pea aphid (Acyrthosiphon pisum) genotypes and their F1 progeny, we filtered for differentially expressed saliva proteins that co-segregated with virulence or avirulence phenotypes. LOC100575698 (ACPISUM_029930), annotated as an uncharacterized protein, was the sole candidate effector for which RNA-Seq and saliva proteomics data showed significantly different expression both between avirulent and virulent parents and between their segregating F1 progeny, with this gene upregulated in avirulent genotypes. BLASTP searches revealed multiple divergent homologs only in genomes of the Aphidomorpha infra-order, suggesting a hitherto undefined ancient aphid-specific gene family. AlphaFold models indicate strong structural similarities but weak sequence homology to chitinases. Because the aphid-specific clade all lack canonical DxxDxDxE motifs for catalytic activity, we designate the proteins as a novel CHitinase-Like (CHL) family. Association of ACPISUM_029930 (ApCHL1) with avirulence was further supported by co-segregating SNPs and a genotype-specific alternatively spliced isoform. We hypothesise that CHL proteins may function similarly to phylogenetically unrelated chitin-binding fungal effectors that sequester chitin, also present in aphid stylets, potentially preventing defence activation through plant chitin receptors and/or blocking chitin degradation by host-secreted chitinases.
Date Issued
2026-02-28
Date Acceptance
2025-10-01
Citation
Molecular Plant-Microbe Interactions, 2026, 39 (1), pp.102-113
ISSN
0894-0282
Publisher
The American Phytopathological Society
Start Page
102
End Page
113
Journal / Book Title
Molecular Plant-Microbe Interactions
Volume
39
Issue
1
Copyright Statement
Copyright © 2026 The Author(s). This work is licensed under a Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/41167599
Subjects
aphid
avirulence
chitinase-like
effector
proteomics
Publication Status
Published
Coverage Spatial
United States
Article Number
MPMI-08-25-0098-R
Date Publish Online
2025-10-30