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Viruses fight back against rn ai technology
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Viruses fight back against rn ai technology

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RNA silencing refers to related processes of post-transcriptional control of gene expression found in plants, animals and fungi. A unifying feature of RNA silencing is that it mediates ...

RNA silencing refers to related processes of post-transcriptional control of gene expression found in plants, animals and fungi. A unifying feature of RNA silencing is that it mediates sequence-specific degradation of target transcripts, recruiting RNA molecules of 21–23 nucleotides as specificity determinants. In higher plants, RNA silencing serves as an adaptive, antiviral defence system, which is transmitted systemically in response to localized virus challenge. Plant viruses have elaborated a variety of counter-defensive measures to overcome the host silencing response. One of these strategies is to produce proteins that target the cell autonomous or signalling steps of RNA silencing. It is not known whether a similar antiviral mechanism also operates in animal cells

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Viruses fight back against rn ai technology Viruses fight back against rn ai technology Presentation Transcript

  • Gaykar Amruta B.
  • PTGS in plants:Discovery of Jorgensen in 1990 AIM: upregulate activity of chsA Expected:more pigments Observed:white sectors Loss of mRNAs of both endo-and transgene (Etienne et al., 2006)
  • RNA interference – gene silencing by double-strandedRNA:The 2006 Nobel Prize for Physiology or Medicine CURRENT SCIENCE, VOL. 91, NO. 11, 10 DECEMBER 2006
  • Mechanism of RNAi Two major pathways involved miRNA Control of endogenous gene expression siRNA Defense against viruses and transposons (Lindbo et al., 2005)
  • Geminivirus induced gene silencing in plants (Ramachandran et. al., 2005)
  • Transgene directed gene silencing in plans  Sense  Antisense  Sense- Antisense (Waterhouse and Helliwell ,2003)
  • Introduction Four major tomato-infecting tospoviruses  TSWV  Groundnut ringspot virus (GRSV)  Tomato chlorotic spot virus (TCSV) and  Watermelon silver mottle virus (WSMoV), in a single small chimaeric hairpin (hp) RNA construct
  • Constructs used in gene silencing
  • Results
  • Suppression of RNA silencing by viral proteins
  • (Miguel, 2007)
  • SGS3-mediated generation of siRNAs
  • Genome organization of RCNMV
  • RNA1 is essential for suppressing RNAi
  • Introduction  BBTV, a circular single-stranded DNA virus  Genus- Babuvirus  Family- Nanoviridae  Multi-segmented genome  B3 and B4,encoded by DNA3 and DNA4 of virus(BBTV), exhibit RNA silencing suppression activity
  • Materials and Methods Plasmids and Agrobacterium  The ORF fragments B1, B3, B4, B5 and B6 of BBTV DNA1, DNA3, DNA4, DNA5, DNA6 were obtained by PCR using primers  The obtained fragments were inserted into pND108 Agroinfiltration and GFP imaging Western blot analysis
  • Transcription cassettes for Agroinfiltration
  •  BBTV B3 , B4 and B5 enhance the pathogenicity of chimeric PVX N. benthamiana leaves infected with chimeric PVX at 14 days post infiltration (dpi)
  • Western blot analysis Accumulation of PVX CP in N. benthamiana leaves
  • N. benthamiana leaves infectedwith chimeric PVX under UVlight at 5 dpi GFP accumulation detected by western blot analysis with anantibody specific for GFP at 5 dpi B3 and B4 reverse established RNA silencing of GFP
  • Results:14 dpi  BBTV B4, but not B3 protein, suppresses systemic gene silencing in newly emerged leaves