Frp1 is a Fusarium oxysporum F‐box protein required for pathogenicity on tomato

Abstract

SummaryFusarium oxysporum f. sp. lycopersici is the causal agent of tomato wilt disease. In order to identify genes involved in its pathogenicity, we performed insertional mutagenesis. Mutant N40 had lost its pathogenicity completely, when tested in bioassays with tomato seedlings. Molecular characterization of mutant N40 revealed that the plasmid insertion had occurred in a gene that codes for a 60.2 kDa protein containing an F-box motif. The gene was therefore designated as FRP1 (F-box protein required for pathogenicity). Targeted FRP1 disruptants had lost their pathogenicity completely, and became fully virulent again upon re-introduction of the FRP1 gene. This confirmed that the FRP1 gene is required for pathogenesis. In a yeast two-hybrid assay Frp1 interacts with Skp1, suggesting involvement of an SCF ubiquitin ligase complex in pathogenicity. FRP1 is constitutively expressed during infection and under different culture conditions. Although growth, spore formation and germination on artificial media were not impaired, confocal laser scanning microscopy of a GFP-marked mutant N40 and a GFP-marked targeted FRP1 disruptant revealed that they were unable to colonize the roots.

Lessons from Fungal F-Box Proteins

“…lycopersici, a vascular wilt pathogen of tomato, Frp1 (F-box protein required for pathogenicity 1) was found using an insertional mutagenesis screen for pathogenicity genes (46). Frp1 is required for assimilation of various (nonsugar) carbon sources as well as induction of genes for cell wall-degrading enzymes, which would explain the deficient plant root colonization and penetration by the ⌬frp1 mutant (W. Jonkers et al, in press).…”

Interplay between ethylene, ETP1/ETP2 F-box proteins, and degradation of EIN2 triggers ethylene responses in Arabidopsis

“…In plants, there are ;700 F-box proteins (Gagne et al 2002), and they are involved in a plethora of biological processes including plant hormone responses (Xie et al 1998;Gray et al 2001;Guo and Ecker 2003;Potuschak et al 2003;Fu et al 2004;Dharmasiri et al 2005;Kepinski and Leyser 2005), lateral root formation (Coates et al 2006), light signaling and clock control (Mas et al 2003;Imaizumi et al 2003Imaizumi et al , 2005, pollen recognition and rejection (Qiao et al 2004a,b;Sijacic et al 2004), and plant-pathogen interactions (Kim and Delaney 2002;Duyvesteijn et al 2005;van den Burg et al 2008). Based on phylogenetic analysis, the superfamily of F-box proteins is divided into 20 groups (Gagne et al 2002).…”

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

“…The construct used for GFP-marking of Fol with GFP behind the constitutive GPD promoter is described elsewhere (Duyvesteijn et al, 2005). For construction of the SIX1-promoter-GFP construct the SIX1 ORF, present in a NcoI-SpeI genomic fragment containing the SIX1 gene in the pGEMT-easy vector, was first replaced by a XbaI restriction site in the following way: in pGEMT-easy containing the NcoI-SpeI fragment with SIX1, the entire SIX1 open reading was deleted and replaced by an XbaI restriction site.…”