Nuclear dynamics and genetic rearrangement in heterokaryotic colonies of Fusarium oxysporum

• Published in: Fungal genetics and biology Vol. 91; pp. 20 - 31
• Main Authors: Shahi, Shermineh, Beerens, Bas, Bosch, Martin, Linmans, Jasper, Rep, Martijn
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.06.2016
• Subjects: carbon; CAT fusion; Cell Nucleus - genetics; Chromosome transfer; chromosomes; Chromosomes, Fungal - genetics; conidia; Conidial anastomosis; eukaryotic cells; fungi; Fusarium - genetics; Fusarium - pathogenicity; Fusarium oxysporum; Gene Rearrangement - genetics; Gene Transfer, Horizontal - genetics; genome; Genome, Fungal - genetics; Green Fluorescent Proteins - genetics; Heterokaryon; histones; hybrids; hyphae; Hyphae - genetics; Hyphae - growth & development; image analysis; Lycopersicon esculentum; Lycopersicon esculentum - microbiology; pathogenicity; pathogens; polymerase chain reaction; progeny; Spores, Fungal - genetics; Spores, Fungal - growth & development; starvation; tomatoes; Conidial anastomosis; CAT fusion; Chromosome transfer; Heterokaryon
• ISSN: 1087-1845; 1096-0937; 1096-0937
• DOI: 10.1016/j.fgb.2016.03.003

[Display omitted] •Conidial anastomosis tube (CAT) fusion in F. oxysporum induced by carbon starvation.•Viable heterokaryons emerge from CAT fusion of incompatible strains.•Chromosome elimination occurs during development of heterokaryotic colonies.•Escape from chromosome elimination can explain horizontal chromosome transfer. Recent studies have shown horizontal transfer of chromosomes to be a potential key contributor to genome plasticity in asexual fungal pathogens. However, the mechanisms behind horizontal chromosome transfer in eukaryotes are not well understood. Here we investigated the role of conidial anastomosis in heterokaryon formation between incompatible strains of Fusarium oxysporum and determined the importance of heterokaryons for horizontal chromosome transfer. Using live-cell imaging we demonstrate that conidial pairing of incompatible strains under carbon starvation can result in the formation of viable heterokaryotic hyphae in F. oxysporum. Nuclei of the parental lines presumably fuse at some stage as conidia with a single nucleus harboring both marker histones (GFP- and RFP-tagged) are produced. Upon colony formation, this hybrid offspring is subject to progressive and gradual genome rearrangement. The parental genomes appear to become spatially separated and RFP-tagged histones, deriving from one of the strains, Fol4287, are eventually lost. With a PCR-based method we showed that markers for most of the chromosomes of this strain are lost, indicating a lack of Fol4287 chromosomes. This leaves offspring with the genomic background of the other strain (Fo47), but in some cases together with one or two chromosomes from Fol4287, including the chromosome that confers pathogenicity towards tomato.