The P25 Pathogenicity Factor of Beet necrotic yellow vein virus Targets the Sugar Beet 26S Proteasome Involved in the Induction of a Hypersensitive Resistance Response via Interaction with an F-box Protein

Abstract

P25, a Beet necrotic yellow vein virus (BNYVV) pathogenicity factor, interacts with a sugar beet protein with high homology to Arabidopsis thaliana kelch repeat containing F-box family proteins (FBK) of unknown function in yeast. FBK are members of the Skp1-Cullin-F-box (SCF) complex that mediate protein degradation. Here, we confirm this sugar beet FBK-P25 interaction in vivo and in vitro and provide evidence for in planta interaction and similar subcellular distribution in Nicotiana tabacum leaf cells. P25 even interacts with an FBK from A. thaliana, a BNYVV nonhost. FBK functional classification was possible by demonstrating the interaction with A. thaliana orthologs of Skp1-like (ASK) genes, a member of the SCF E3 ligase. By means of a yeast two-hybrid bridging assay, a direct effect of P25 on SCF-complex formation involving ASK1 protein was demonstrated. FBK transient Agrobacterium tumefaciens-mediated expression in N. benthamiana leaves induced a hypersensitive response. The full-length F-box protein consists of one F-box domain followed by two kelch repeats, which alone were unable to interact with P25 in yeast and did not lead to cell-death induction. The results support the idea that P25 is involved in virus pathogenicity in sugar beet and suggest suppression of resistance response.

Ubiquitin and Plant Viruses, Let’s Play Together!

“…Yeast two-hybrid experiments evidenced the interaction of P25 with a number of candidate proteins involved in ubiquitination (Thiel and Varrelmann, 2009), in particular a protein containing an F-box domain and two Kelch repeats. The biological relevance of BNYVV P25 in terms of degradation remains unclear, but rather than P25 being a substrate of this host F-box protein, it has been proposed that P25 might inhibit the interaction between the SKP1 homolog ASK1 and the F-box protein, thereby altering proper target recognition and leading to cell necrosis in an as yet undefined manner (Thiel et al, 2012).…”

Chlorovirus Skp1-Binding Ankyrin Repeat Protein Interplay and Mimicry of Cellular Ubiquitin Ligase Machinery

“…Several ubiquitin-interfering viral proteins interact directly with E3 family enzymes, in particular the cullin-based RING (really interesting new gene) finger-type ubiquitin ligase (CRL) SCF (Skp1, cullin, F-box) complex (4,5). The F-box protein is one of the four subunits of the SCF complex which mediates target recruitment for ubiquitination.…”

Evaluation of rhizomania-resistance segregating sequences and overall genetic diversity pattern among selected accessions of Beta and Patellifolia. Potential implications of breeding for genetic bottlenecks in terms of rhizomania resistance

“…We performed also high resolution melting analysis (HRM) after PCR for one of the products in order to identify potential Rz2-accompanying polymorphisms described earlier (Thiel et al 2012). As a result we found that one of the resistant cultivars repeatedly clustered with the susceptible-like profile as far as this sequence is concerned, displaying a heterozygote-like HRM profile (Fig.…”