A single gene in Fusarium oxysporum limits host range

Area of Science:

• Plant Pathology
• Molecular Biology
• Genetics

Background:

• Fusarium oxysporum comprises various formae speciales (e.g., F. oxysporum f. sp. radicis-cucumerinum (Forc) and F. oxysporum f. sp. melonis (Fom)) with distinct host ranges.
• Mobile chromosomes in Forc and Fom have been previously implicated in determining their differing host specificities.
• Understanding the genetic basis of host specificity is crucial for managing plant diseases caused by Fusarium oxysporum.

Purpose of the Study:

• To identify specific genes responsible for the difference in host range between Forc and Fom.
• To investigate the role of a candidate effector gene in determining Fusarium oxysporum host specificity.

Main Methods:

• Comparative analysis of pathogenicity chromosomes between Forc and Fom.
• RNA-sequencing to identify candidate genes involved in host range.
• Functional analysis of a candidate effector gene through genetic transformation experiments in Forc.

Main Results:

• Eleven candidate genes were selected for testing, including a putative effector gene unique to the Fom pathogenicity chromosome.
• Transforming Forc with the Fom effector gene resulted in significantly reduced or abolished pathogenicity towards cucumber.
• The transformed Forc strains retained pathogenicity towards melon and watermelon, indicating a specific role in cucumber interaction.

Conclusions:

• A single effector gene from Fom determines host specificity, being recognized by the cucumber plant's immune system.
• This study provides the first evidence of a single gene dictating host specificity differences between Fusarium oxysporum formae speciales.
• The findings offer new insights into the molecular mechanisms underlying plant-pathogen interactions and host specialization.