Molecular characterization of Pvr9 that confers a hypersensitive response to Pepper mottle virus (a potyvirus) in Nicotiana benthamiana

- Pvr9 from peppers confers a hypersensitive response to PepMoV in N. benthamiana.
- Pvr9 is located on pepper chromosome 6 and putatively encodes for 1298 amino acids.
- NIb is the elicitor of the Pvr9-mediated hypersensitive response.
- Important amino acid residues for function of Pvr9 and the elicitor NIb are determined through mutagenesis analyses.

There are some R genes against potyviruses which were mapped in pepper. However, none of them has been characterized at the molecular level. In this study, we characterized Pvr9 which is an Rpi-blb2 ortholog from pepper and confers a hypersensitive response to Pepper mottle virus (PepMoV) in a transient expression system in Nicotiana benthamiana. This gene putatively encoded for 1298 amino acids and is located on pepper chromosome 6. PepMoV NIb was the elicitor of the Pvr9-mediated hypersensitive response. NIb from several other potyviruses also elicited the hypersensitive response. Inoculation of pepper with PepMoV resulted in a minor increase in Pvr9 transcription in the resistant cultivar CM334 and a slight down-regulation in the susceptible cultivar Floral Gem. The 5′ upstream region of Pvr9 from cultivar CM334 had higher transcription activity than the region from cultivar Floral Gem. The cultivars CM334 and Floral Gem had non-functional Pvr9 homologs with loss-of-function mutations.