ABSTRACT
Horizontal pollen transmission by the raspberry bushy dwarf virus 1b deletion mutant (RBΔ1bstop), which is defective in virus virulence, was significantly decreased compared to wild-type raspberry bushy dwarf virus (wtRBDV). We assessed accumulation of viral genomic (g) RNAs in pollen grains from RBΔ1bstop-infected plants and found that the pollen grains had less viral gRNA than those from wtRBDV-infected plants. In addition, pollen grains from 1b-expressing transgenic plants (1b-plants) infected with RBΔ1bstop were more efficient in horizontal virus transmission to healthy plants after pollination than pollen from RBΔ1bstop-infected wild type plants. Moreover, viral gRNA accumulation in pollen grains from RBΔ1bstop-infected 1b-plants was higher than in pollen from RBΔ1bstop-infected wild type plants. We suggest that 1b increases the amount of viral gRNAs released from elongating pollen grains.
Subject(s)
Genes, Viral , Plant Diseases/virology , Plant Viruses/genetics , Pollen/virology , Rubus/virology , Disease Transmission, Infectious , In Situ Hybridization , Mutation , Plant Viruses/pathogenicity , Plants, Genetically Modified , Pollination , RNA Viruses/genetics , RNA Viruses/pathogenicity , RNA, Viral/genetics , RNA, Viral/metabolism , Rubus/physiology , Nicotiana/genetics , Nicotiana/physiology , Nicotiana/virologyABSTRACT
A product translated from the 1b gene of raspberry bushy dwarf virus (RBDV) was specifically detected in RBDV-infected Nicotiana benthamiana plants by immunoblot analysis. To analyze the effects of the 1b gene on virus infection in host plants, an RBDV deletion mutant virus (RB∆1bstop), which is unable to express the 1b gene, was constructed and inoculated to N. benthamiana plants. The results showed that accumulation of the virus genomic (g) RNAs 1 and 2 decreased in inoculated leaves, and that systemic virus spread was delayed compared with wild-type RBDV. In contrast, accumulation of the viral gRNAs 1 and 2 was elevated in RB∆1bstop-infected leaf tissues during ectopic expression of the 1b gene. Furthermore, we found that the 1b has weak RNA silencing suppressor activity.