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Viral resistance

Viral resistance



biotic resistance towards plant

biotic resistance towards plant



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    Viral resistance Viral resistance Presentation Transcript

    • Viral resistance
    • STRESS Abiotic Component Biotic Component Sunlight  Salt concentration  Drought conditions  Temperatures  Soil condition  Oxidative agents  Cold conditions  Metal toxicity   Virus  Fungal pathogens  Bacteria  Nematodes  Insects  Weed  Parasitic angiosperms
    • INFECTED LEAF Biotic Stress – viruses  Modes of virus resistances  Viral coat protein mediated  Antisense  Ribozymes  Satellite sequences  Non structural protein resistance  Gene silencing 
    • Coat protein mediated cross protection Ability of first virus to prevent the effect of second virus.  Sanford and Johnston (1985)  Powell – Abel et al.(1986)  Part of viral genome  Focused on codes of coat protein of TMV  Well studied + easily transformed by Agrobacterium tumefaciens . 
    • Cont…..  CP coding seq Engineered CP coding seq cassette vector (pMON316) * 35 CaMV promoter * NOS terminator signal  In agrobacterial cells  Tobacco leaf disc – kanamycin medium  Plant with TMV Notes:- 3:1 ratio, increased infection = late symptoms
    • Non structural protein mediated resistances Non structural “replicase” protein  54 kDa ORF of TMV – Golemboski et al. (1990)  Pinto et al. (1999) oped rice yellow mosaic virus resistant transgenic crop by replicase.  Eg. Tobacco, potato, tomato, soybean, rice, citrus , orange, maize – CP TMV, AMV and TRV. 
    • Cont….. Milton Zaitlin’s lab, cornell University , Golemboski et al, 1990 – gene of viral replicase.  Use tobacco – 3 terminal TMV 54 kDa used for encoding repilcase.  MacFarlene and Davies (1992) similar expt.  Not clear mechanism – not effective. 
    • Antisense RNAs A Complementary DNA strand of a gene can be inserted in reverse orientation this is referred as antisense gene.  mRNA by normal gene complementary to mRNA of antisense gene.  Hybridize  Block the specific gene expression.  Sanford and Johnston (1985).  Eg. Beta 1,3-glucanase was down regulated by antisense RNA in Tobacco + tolerance mosaic virus+ delayed spread+ reduced virus yield. 
    • Ribozymes Ribozymes are small RNA molecules – catalytic cleavage of target RNA  Block the replication of RNA.  But not effective . 
    • Movement proteins rapid spread of virus.  30kDa protein of TMV  32 kDa protein of brome mosaic virus  transgenic tobacco plant – mutated 30kDa of MP.  hence competes with TMV virus  Develop resistance  Malyashenko et al (1993) – has cDNA thermal mutant MP of TMV showed resistances at 33̇͘ but not at 24˚c. ˚c 
    • Satellite sequences  Small RNA molecules that are unable to multiple in host cell without helper virus.  Not in replication but affect diseases symptoms  cucumber mosaic virus cucumovirus (CMV) symptoms – reduced – carrying satellite  Transgenic tobacco and tomato plant with CMV satellites – china – (1990 - 1992)  not good- sever disease symptoms  Satellites mutates very fast  Recombination bt satellites – serious
    • Mechanism of post-transcriptional gene silencing (PTGS)
    • Gene silencing in transgenic plants It was firstly reported when introduction of additional chalcone synthase gene was transformed to petunia flower to intensify the voilet color of flower  Obtained flowers (transgenic lines) were both 1. intensed violet colered type- transgenesis worked 2. and white colored as well-Both native and transgenic chalcone synthase turned off  Stable integration and expression of transgene is required for commercial exploitation.  Expression of introduced gene can be abberant - GENE SILENCING!!! 
    • bhendi yellow vein mosaic virus – gene silening in varoius plant
    • References H.S Chawla, Introduction to plant Biotechnology(2002) oxford and IBH publishing co. pvt ltd.  U. Satayanaryana, Book of Biotechnology (2010) 6th ,Uppala author-publish interlinks. John barton, transgenic plants (1992), imperial college press. A.Slater, N.Scott and M.Fowler, Plant biotechnology (2003),oxford university press. Google images. 