RNAi-mediated transgenic Tospovirus resistance broken by intraspecies silencing suppressor protein complementation.
Extension of an inverted repeat transgene cassette, containing partial nucleoprotein (N) gene sequences from four different tomato-infecting Tospovirus spp. with a partial N gene sequence from the tomato strain of Tomato yellow ring virus (TYRV-t), renders transgenic Nicotiana benthamiana plants additionally resistant to this strain but not to the soybean strain of this Tospovirus sp. (TYRV-s), both strains exhibiting 14.4% nucleotide sequence divergence in their N genes. Surprisingly, coinoculation of the TYRV-t-resistant transgenic lines with both TYRV-t and TYRV-s resulted in rescue of the former. Mass-spectrometric analysis of the viral ribonucleocapsids accumulating in the transgenic plants showed the presence of the N proteins of both strains excluding hetero-encapsidation as rescue mechanism and indicating suppression of TYRV-t N gene transcript breakdown by RNA interference. Prior (Potato virus X [PVX]-vector-mediated) expression of the TYRV-s silencing suppressor (NS(s)) gene also allowed TYRV-t to break the resistance. This phenomenon was also observed when the homologous (TYRV-t) NS(s) gene was provided from a PVX replicon, demonstrating that TYRV can break RNA-mediated host resistance upon a priori expression of its NS(s) protein. Remarkably, mixed inoculation of TYRV-t with other Tospovirus spp. or nonrelated viruses did not result in resistance breaking, indicating that the rescuing activity of NS(s)-though based on suppressing RNA silencing-is species-dependent.
Hassani-Mehraban
Afshin
A
Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD, Wageningen, The Netherlands.
Brenkman
A B
AB
van den Broek
N J F
NJ
Goldbach
Rob
R
Kormelink
Richard
R
D000595:Amino Acid Sequence; D001483:Base Sequence; D004279:DNA, Viral / Q000235:genetics; D005814:Genes, Viral; D005816:Genetic Complementation Test; D054884:Host-Pathogen Interactions / Q000235:genetics; D018551:Solanum lycopersicum / Q000235:genetics / Q000821:virology; D008969:Molecular Sequence Data; D019590:Nucleocapsid Proteins / Q000235:genetics; D010935:Plant Diseases / Q000235:genetics / Q000821:virology; D010940:Plant Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D013489:Suppression, Genetic; D014026:Nicotiana / Q000235:genetics* / Q000821:virology*; D017865:Tospovirus / Q000235:genetics* / Q000472:pathogenicity*
D004279:DNA, Viral; D019590:Nucleocapsid Proteins; D010940:Plant Proteins; D034741:RNA, Small Interfering