Expression of effector gene SIX1 of Fusarium oxysporum requires living plant cells

• Published in: Fungal genetics and biology 2008-09, Vol.45 (9), p.1257-1264
• Main Authors: van der Does, H. Charlotte, Duyvesteijn, Roselinde G.E., Goltstein, Pieter M., van Schie, Chris C.N., Manders, Erik M.M., Cornelissen, Ben J.C., Rep, Martijn
• Format: Article
• Language: English
• Subjects: Avirulence; Cells, Cultured; Confocal microscopy; cultured cells; dead plant material; effector genes; fungal proteins; Fungal Proteins - analysis; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fusarium - chemistry; Fusarium - genetics; Fusarium - metabolism; Fusarium oxysporum; gene expression; gene expression regulation; Gene Expression Regulation, Fungal; Green fluorescent protein; Green Fluorescent Proteins - analysis; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; host plants; infection; living plant material; Lycopersicon esculentum - microbiology; microbial colonization; pathogenicity; Plant Diseases - microbiology; plant morphology; plant pathogenic fungi; Plant Roots - microbiology; protein synthesis; Recombinant Fusion Proteins - analysis; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; rhizosphere; Root colonization; Tomato; Two-photon microscopy; Xylem - chemistry; Xylem - genetics; Xylem - metabolism
• ISSN: 1087-1845; 1096-0937
• DOI: 10.1016/j.fgb.2008.06.002

Fusarium oxysporum is an asexual, soil inhabiting fungus that comprises many different formae speciales, each pathogenic towards a different host plant. In absence of a suitable host all F. oxysporum isolates appear to have a very similar lifestyle, feeding on plant debris and colonizing the rhizosphere of living plants. Upon infection F. oxysporum switches from a saprophytic to an infectious lifestyle, which probably includes the reprogramming of gene expression. In this work we show that the expression of the known effector gene SIX1 of F. oxysporum f. sp. lycopersici is strongly upregulated during colonization of the host plant. Using GFP (green fluorescent protein) as reporter, we show that induction of SIX1 expression starts immediately upon penetration of the root cortex. Induction requires living plant cells, but is not host specific and does not depend on morphological features of roots, since plant cells in culture can also induce SIX1 expression. Taken together, F. oxysporum seems to be able to distinguish between living and dead plant material, preventing unnecessary switches from a saprophytic to an infectious lifestyle.