Characterization of resistance mechanism in transgenic Nicotiana benthamiana containing Turnip crinkle virus coat protein

Plant Cell Rep. 2008 Nov;27(11):1731-40. doi: 10.1007/s00299-008-0595-9. Epub 2008 Aug 14.

Abstract

Two transgenic lines, of Nicotiana benthamiana expressing Turnip crinkle virus (TCV)-coat protein (CP) gene with contrasting phenotype, the highest (#3) and the lowest (#18) CP expressers, were selected and challenged with the homologous TCV. The former, the highest expresser, showed nearly five times more CP expression than the latter. Progenies of #3 and #18 lines showed 30 and 100% infection rates, respectively. The infected progenies of #3 line showed mild and delayed symptom with TCV. This is a coat protein-mediated resistance (CP-MR), and its resistance level is directly proportional to CP transgene expression. However, CP-MR of the transgenic plants was specific only for TCV but not for heterologous viruses. Newly growing leaves of those infected progenies of #3 line did not show any visible symptoms at 4-week post-inoculation (wpi) with TCV, suggesting a reversal from infection. This was confirmed by RT-PCR analysis with the disappearance of the target at 4 wpi. This is a case of RNA-mediated resistance, and a threshold level of transgene expression may be needed to achieve the silent state. To confirm the RNA silencing, we infiltrated Agrobacterium carrying TCV-CP into leaves of progenies of #3 and performed RT-PCR analysis. The results indicate that TCV-CP's suppressor activity against RNA silencing itself can be silenced by the homologous expression of TCV-CP in the transgenic plants. The transgenic plants containing TCV-CP seem to be a model system to study viral protection mediated by a combination of protein and RNA silencing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Blotting, Western
  • Capsid Proteins / genetics*
  • Carmovirus / genetics*
  • DNA Primers
  • Enzyme-Linked Immunosorbent Assay
  • Nicotiana / genetics*
  • Nicotiana / virology
  • Plants, Genetically Modified / genetics*
  • Plants, Genetically Modified / virology
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transcription, Genetic

Substances

  • Capsid Proteins
  • DNA Primers