FoCup, a secreted protein, is essential for virulence of Fusarium oxysporum f. sp. cucumerinum on cucumber

Author: mycolabadmin
12/17/2025
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Summary

Researchers identified a key protein called FoCup that helps a fungal pathogen infect cucumber plants and cause devastating wilt disease. By deleting this protein from the fungus, scientists significantly reduced its ability to cause disease and produce spores needed for spreading. This discovery could help develop new ways to protect cucumber crops by targeting this critical virulence factor.

Background

Fusarium oxysporum f. sp. cucumerinum (Foc) causes devastating wilt disease in cucumber worldwide, resulting in 10-30% annual incidence and substantial crop losses. Conventional management strategies have limited efficacy due to the pathogen’s soil persistence and the complexity of breeding disease-resistant cultivars. Understanding Foc pathogenic mechanisms through identification of virulence effectors is critical for developing sustainable control measures.

Objective

This study aimed to identify and functionally characterize FoCup, a novel secreted protein effector that was highly upregulated during Foc-cucumber interactions according to transcriptomic data. The researchers sought to determine FoCup’s role in fungal virulence, conidiation, and stress tolerance through genetic and molecular approaches.

Results

FoCup contains an N-terminal signal peptide and a cupredoxin domain, and was confirmed as a secreted protein that localizes to the plasma membrane. Δ FoCup knockout mutants exhibited significantly reduced virulence (54.5-62.5% decrease in disease index), decreased conidiation, and increased sensitivity to osmotic stressors (glycerol, sorbitol, NaCl, KCl), while mycelial growth remained normal. Virulence and conidiation were fully restored in complementation mutants.

Conclusion

FoCup represents the first identified secreted protein with a cupredoxin domain in Fusarium and plays a critical role in Foc pathogenesis on cucumber. The protein influences both conidiation and virulence despite being located on a core chromosome, making it a promising target for chemical control and warranting further investigation of its mechanisms in sporulation and host infection.

Published in:Frontiers in Microbiology,
Study Type:Experimental Study,
Source: PMID: 41480111, DOI: 10.3389/fmicb.2025.1728884