A viral resistance gene from common bean functions across plant families and is up-regulated in a non-virus-specific manner.
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.
Seo
Young-Su
YS
Department of Plant Pathology and Section of Plant Biology, University of California, Davis, CA 95616, USA.
Rojas
Maria R
MR
Lee
Jung-Youn
JY
Lee
Sang-Won
SW
Jeon
Jong-Seong
JS
Ronald
Pamela
P
Lucas
William J
WJ
Gilbertson
Robert L
RL
D003001:Cloning, Molecular; D017799:Cucumovirus / Q000378:metabolism; D007887:Fabaceae / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005814:Genes, Viral; D008957:Models, Genetic; D016297:Mutagenesis, Site-Directed; D009336:Necrosis; D010935:Plant Diseases / Q000235:genetics*; D030821:Plants, Genetically Modified; D012313:RNA / Q000737:chemistry; D019076:Transgenes; D015854:Up-Regulation
D012313:RNA