title: Participation of the Cowpea mosaic virus protease in eliciting extreme resistance.
abstract: Extreme resistance of Arlington line cowpea (Vigna unguiculata) to Cowpea mosaic virus (CPMV) is under control of a dominant locus designated Cpa. We transiently expressed, using Tomato bushy stunt virus (TBSV) vectors and Agrobacterium tumefaciens, in nearly isogenic Cpa/Cpa and cpa/cpa cowpea lines, sequences from RNA1, the larger of two CPMV genomic RNAs. Activation of a Cpa-specific response mapped to the CPMV 24K protease (24KPro). Mutational analysis of the 24KPro gene implicated protease activity, rather than 24KPro structure, in Cpa-mediated recognition of CPMV invasion. A 24KPro with alanine replacing the active site cysteine [24KPro(C-A)], but not wildtype 24KPro, accumulated after agroinfiltration of the corresponding binary vector constructions into Cpa/Cpa cowpea. In cpa/cpa cowpea, both protease versions accumulated, with 24KPro(C-A) in greater abundance. Thus, enzymically active 24KPro was recognized by both cowpea genotypes, but in Cpa/Cpa cowpea the suppression of 24KPro accumulation was very strong, consistent with extreme resistance to CPMV.
authors.affiliation: Department of Plant Pathology, College of Agricultural and Environmental Sciences, University of California, Davis, CA 95616, USA.
authors.forename: Qiuling
authors.initials: Q
authors.lastname: Fan
authors.forename: Mohan
authors.initials: M
authors.lastname: Niroula
authors.forename: Paul A
authors.initials: PA
authors.lastname: Feldstein
authors.forename: George
authors.initials: G
authors.lastname: Bruening
mesh_terms: D017798:Comovirus / Q000201:enzymology*; D007887:Fabaceae / Q000502:physiology*; D015967:Gene Expression Regulation, Viral; D020022:Genetic Predisposition to Disease; D005822:Genetic Vectors; D016679:Genome, Viral; D005838:Genotype; D009154:Mutation; D010447:Peptide Hydrolases / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology / Q000821:virology*; D057865:Plant Immunity / Q000502:physiology; D018515:Plant Leaves; D012231:Rhizobium / Q000235:genetics / Q000378:metabolism
chemical_list: D010447:Peptide Hydrolases