viral resistance gene from common bean functions across plant families and is up-regulated in a non-virus-specific manner

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 103; no. 32; pp. 11856 - 11861
• Main Authors: Seo, Y.S, Rojas, M.R, Lee, J.Y, Lee, S.W, Jeon, J.S, Ronald, P, Lucas, W.J, Gilbertson, R.L
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 08-08-2006; National Acad Sciences
• Subjects: Bean dwarf mosaic virus; Beans; Biological Sciences; Botany; Cloning, Molecular; Cucumber mosaic virus; Cucumovirus - metabolism; Cytomegalovirus; disease resistance; Fabaceae - metabolism; Geminivirus; Gene Expression Regulation, Plant; gene induction; gene up-regulation; Genes; Genes, Plant; Genes, Viral; Leaves; Lycopersicon esculentum; Models, Genetic; Mutagenesis, Site-Directed; Necrosis; Nicotiana benthamiana; Pathogens; Phaseolus vulgaris; Phenotypes; Plant Diseases - genetics; plant diseases and disorders; Plant resistance; Plants, Genetically Modified; Polymerase chain reaction; resistance mechanisms; Reverse transcriptase polymerase chain reaction; RNA; RNA - chemistry; RT-4 gene; strain differences; systemic necrosis; Transgenes; Transgenic plants; Up-Regulation; Viruses
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0604815103

Genes involved in a viral resistance response in common bean (Phaseolus vulgaris cv. Othello) were identified by inoculating a geminivirus reporter (Bean dwarf mosaic virus expressing the green fluorescent protein), extracting RNA from tissue undergoing the defense response, and amplifying sequences with degenerate R gene primers. One such gene (a TIR-NBS-LRR gene, RT4-4) was selected for functional analysis in which transgenic Nicotiana benthamiana were generated and screened for resistance to a range of viruses. This analysis revealed that RT4-4 did not confer resistance to the reporter geminivirus; however, it did activate a resistance-related response (systemic necrosis) to seven strains of Cucumber mosaic virus (CMV) from pepper or tomato, but not to a CMV strain from common bean. Of these eight CMV strains, only the strain from common bean systemically infected common bean cv. Othello. Additional evidence that RT4-4 is a CMV R gene came from the detection of resistance response markers in CMV-challenged leaves of RT4-4 transgenic plants, and the identification of the CMV 2a gene product as the elicitor of the necrosis response. These findings indicate that RT4-4 functions across two plant families and is up-regulated in a non-virus-specific manner. This experimental approach holds promise for providing insights into the mechanisms by which plants activate resistance responses against pathogens.