Comprehensive functional mapping of accessory chromosomes identifies a dominant virulence-regulator paralog in tomato wilt pathogen
- 1Tokyo University of Agriculture and Technology (TUAT)
Abstract
Accessory chromosomes (ACs) serve as flexible genomic compartments that facilitate rapid adaptive evolution in eukaryotic microbes. In the tomato wilt pathogen Fusarium oxysporum f. sp. lycopersici, ACs are essential for virulence and host specificity; however, their structural complexity and functional redundancy have hindered a systematic characterization of their distinct roles. Here, we established a CRISPR/Cas9-based chromosomal dissection platform to generate a comprehensive functional map of pathogenicity determinants within ACs. Using this platform, we successfully generated a library of 36 large deletion mutants across the approximately 10 Mb putative AC region, enabling a chromosome-scale functional characterization of these compartments. A systematic screen of this library identified seven discrete AC segments that are indispensable for full virulence toward tomato. High-resolution chromosomal dissection of one virulence-associated segment through iterative subdivision and targeted gene disruption revealed that FTF1a-1, a single member of the Fusarium transcription factor 1 (FTF1) family that originated from the duplication of core-chromosomal virulence gene FTF2 into the AC region, functions as a dominant regulator of virulence. Given that the FTF1a-3 paralog contributes only marginally to virulence and the deletion of other paralogs does not markedly affect disease development, our findings demonstrate a functional hierarchy within the duplicated FTF1 gene family. These results imply that neofunctionalization of virulence genes within plastic fungal genomes promotes hyper-virulence and drives host-specific adaptation in F. oxysporum.
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BibTeX
@misc{yamazaki2026comprehensive,
title = {{Comprehensive functional mapping of accessory chromosomes identifies a dominant virulence-regulator paralog in tomato wilt pathogen}},
author = {M. Yamazaki and H. Saito and S. Asai and T. Kamakura and K. Komatsu and T. Arazoe and T. Arie},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.08.750270},
url = {https://www.biorxiv.org/content/10.64898/2026.09.08.750270v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Comprehensive functional mapping of accessory chromosomes identifies a dominant virulence-regulator paralog in tomato wilt pathogen
AU - M. Yamazaki
AU - H. Saito
AU - S. Asai
AU - T. Kamakura
AU - K. Komatsu
AU - T. Arazoe
AU - T. Arie
PY - 2026
DA - 2026/09/08
PB - bioRxiv
DO - 10.64898/2026.09.08.750270
UR - https://www.biorxiv.org/content/10.64898/2026.09.08.750270v1
AB - Accessory chromosomes (ACs) serve as flexible genomic compartments that facilitate rapid adaptive evolution in eukaryotic microbes. In the tomato wilt pathogen Fusarium oxysporum f. sp. lycopersici, ACs are essential for virulence and host specificity; however, their structural complexity and functional redundancy have hindered a systematic characterization of their distinct roles. Here, we established a CRISPR/Cas9-based chromosomal dissection platform to generate a comprehensive functional map of pathogenicity determinants within ACs. Using this platform, we successfully generated a library of 36 large deletion mutants across the approximately 10 Mb putative AC region, enabling a chromosome-scale functional characterization of these compartments. A systematic screen of this library identified seven discrete AC segments that are indispensable for full virulence toward tomato. High-resolution chromosomal dissection of one virulence-associated segment through iterative subdivision and targeted gene disruption revealed that FTF1a-1, a single member of the Fusarium transcription factor 1 (FTF1) family that originated from the duplication of core-chromosomal virulence gene FTF2 into the AC region, functions as a dominant regulator of virulence. Given that the FTF1a-3 paralog contributes only marginally to virulence and the deletion of other paralogs does not markedly affect disease development, our findings demonstrate a functional hierarchy within the duplicated FTF1 gene family. These results imply that neofunctionalization of virulence genes within plastic fungal genomes promotes hyper-virulence and drives host-specific adaptation in F. oxysporum.
ER -