The Dual Role of the Potyvirus P3 Protein ofTurnip mosaic virusas a Symptom and Avirulence Determinant in Brassicas

Abstract

Two isolates of the potyvirus Turnip mosaic virus (TuMV), UK 1 and CDN 1, differ both in their general symptoms on the susceptible propagation host Brassica juncea and in their ability to infect B. napus lines possessing a variety of dominant resistance genes. The isolate CDN 1 produces a more extreme mosaic in infected brassica leaves than UK 1 and is able to overcome the resistance genes TuRB01, TuRB04, and TuRB05. The resistance gene TuRB03, in the B. napus line 22S, is effective against CDN 1 but not UK 1. The nucleic acid sequences of the UK 1 and CDN 1 isolates were 90% identical. The C-terminal half of the P3 protein was identified as being responsible for the differences in symptoms in B. juncea. A single amino acid in the P3 protein was found to be the avirulence determinant for TuRB03. Previous work already has identified the P3 as an avirulence determinant for TuRB04. Our results increase the understanding of the basis of plant-virus recognition, show the importance of the potyviral P3 gene as a symptom determinant, and provide a role in planta for the poorly understood P3 protein in a normal infection cycle.

Mapping and candidate-gene screening of the novel Turnip mosaic virus resistance gene retr02 in Chinese cabbage (Brassica rapa L.)

“…TuRB04 and TuRB05 (Jenner et al , 2003, TuRB01b (Rusholme 2000), and retr01 and ConTR01 (Rusholme 2000;Rusholme et al 2007). These genes were mapped with RFLP, AFLP, and SSR markers.…”

“…Most of the genes mapped in brassicas are specific to certain TuMV isolates, being found in B. napus and B. rapa . Most of them are dominant, such as TuRB01 , TuRB03 (Hughes et al 2003), TuRB04-05 (Jenner et al , 2003, and TuRB01b (Rusholme 2000). TuRB01 is a single dominant resistance gene and was the first TuMV resistance gene described in Brassica.…”

An overlapping essential gene in the Potyviridae

“…1), is a Ϸ42-kDa nonstructural protein and is one of the least well characterized Potyvirus proteins. It may be involved in virus replication, pathogenicity, resistance breaking, and systemic infection (6,9,(21)(22)(23). It is interesting that previous investigations into the function and localization of P3 have produced conflicting results (6).…”

Identification of amino acids of the beet necrotic yellow vein virus p25 protein required for induction of the resistance response in leaves of Beta vulgaris plants

“…In one case, an RNA sequence was also shown to act as an Avr factor (Szittya & Burgyan, 2001). Some of these Avr determinants have been reported to function as pathogenic determinants; for instance, turnip crinkle virus CP (Ren et al, 2000;Qu et al, 2003), cucumovirus 2b protein (Li et al, 1999), cauliflower mosaic virus transactivator/viroplasmin protein (Kobayashi & Hohn, 2004) and potyvirus P3 protein (Johansen et al, 2001;Jenner et al, 2003).…”