ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Microbe and Virus Interactions with Plants
This article is part of the Research TopicEpigenetic modification in plant-pathogen interactions: Role, Mechanism, Disease ManagementView all 3 articles
FoCup, a secreted protein, is essential for virulence of Fusarium oxysporum f. sp. cucumerinum on cucumber
Provisionally accepted
- 1Shenyang Agricultural University College of Horticulture, Shenyang, China
- 2Chinese Academy of Agricultural Sciences State Key Laboratory for Biology of Plant Diseases and Insect Pests, Beijing, China
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Fusarium oxysporum f. sp. cucumerinum (Foc) infected cucumber (Cucumis sativus), leading to serious wilt disease and great economical losses worldwide. During infection, Foc secreted various protein effectors to facilitate colonization and disease development. Here, we identified a novel virulence effector, designated FoCup, which was highly up-regulated during Foc-cucumber interactions according to transcriptomic data. Bioinformatic analysis using SignalP-5.0 and InterPro predicted an N-terminal signal peptide and a cupredoxin domain in FoCup. Phylogenetic analysis indicated that FoCup is highly conserved within the Fusarium genus. Its secretory capability was experimentally confirmed by the yeast invertase secretion assay. Subcellular localization in Nicotiana benthamiana leaf cells revealed that FoCup-GFP predominantly localized to the plasma membrane, co-localizing with the membrane marker CD3-1007 (AtPIP2A-mCherry). Functional characterization demonstrated that Δ FoCup knockout mutants exhibited significantly reduced virulence on cucumber, accompanied by decreased conidiation, and increased sensitivity to osmotic stressors (e.g., glycerol, sorbitol, NaCl, KCl). In contrast, mycelial growth remained comparable to the wild-type (WT) strain. The impaired virulence and conidiation in the knockout mutants (ΔFoCup) were fully restored in the complementary mutants (ΔFoCup+FoCup). Specifically, pathogenicity tests showed that the disease index caused by ΔFoCup was significantly reduced by 54.5and 62.5 compared to the wild type Foc, underscoring the critical role of FoCup in pathogenesis. Our findings provide new insights into the molecular mechanisms underlying Foc virulence.
Keywords: Fusarium oxysporum f. sp. cucumerinum, cucumber, Virulence, effector, Cupredoxin domain
Received: 20 Oct 2025; Accepted: 27 Nov 2025.
Copyright: © 2025 Xu, Liu, Li, Guo, Sun, Yu, Sun and Lu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Chao-Ge Yu
Zhou-Ping Sun
Xiao-Hong Lu
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