Pathogen-Derived Resistance: A Promising Avenue for Controlling Plant Virus Diseases Buhari Lawan Muhammad, Bello Hassan Jakada, Tahir Abdulqadir Ahmad. Jodhpur National University (JNU), Department of Botany. Jhanwar Road Near Boranada, Jodhpur Rajasthan. buharilawan20@gmail.com Pathogen-Derived Resistance Transgenic Plants Introduction Figure 1: Schematic representation of a plant virus and its life cycle in a plant cell. (Jackson et al., 1993). Plant Virus diseases causes many important plant diseases and are responsible for huge losses in crop production and quality in all parts of the world. Diseases caused by plant viruses are difficult to manage. The concept of pathogen-derived resistance has stimulated research on obtaining virus resistance through genetic engineering. Is a way in which plants can be protected from diseases with trangenes that are derived from the pathogen themselves, a concept refer to as Pathogen-derived resistance. a b Figure 5: (a) Typical Mosaisc pattern on flued cured tobacco leaves infected with tobacco Mosaic virus. Source: www. Apsnet.org (b)An early, clear demonstration of coat-protein mediated resistance against TMV in transgenic plants. Each of the plants was inoculated with a severe yellow strain of TMV ten days prior to the photograph (Beachy, 1999). Mechanism of Pathogen-Derived Resistance to Virus in Transgenic Plants Transgenic CP Reassembly Challenge Virus 5’ end RNA Several approaches have been used to engineer plants for virus resistance, which are as follows: Coat protein Mediated Resistance, cDNA of satellite RNA, Defective viral genome, Antisense RNA approach, and Ribozyme-mediated protection Replicase Figure 2. Computer-assisted graphic representation of a model that shows the predicted interactions between transgenic TMV CP (orange, upper) and challenge virus (grey, lower) that are involved in coat-protein-mediated resistance (from Bendahmane & Beachy 1998). Insert Tables or Images of artwork, etc. Figure 3. The strategies of plant virus resistance Source: NTU : Institute of Biotechnology hompage.ntu.edu.tw/-linss01/ c a b Figure 6: (a)Transgenic papaya plants show resistance (right) while non-transgenic plants (left) are susceptible to papaya ringspot virus under field conditions. (b) Farmer displaying healthy transgenic papaya fruit in Thailand. (c) Transgenic tomato plants show resistance (left) while non-transformed plants are susceptible to cucumber mosaic virus under field conditions (Right). Source: (Meng and Gubba 2000). Antisense RNA-Mediated Resistance Conclusions The antisense RNA is thought to form a duplex with the target viral RNA by hybridization. The duplexes formed may stimulate degradation of the mRNA by RNAses or could prevent binding of the ribosome, thereby impeding translation into proteins. Coat Protein-Mediated Protection (CPMP) Pathogen-Derived resistance has been used to control Important plant virus diseases. Coat Protein mediated Protection (CPMP) has been reported for Tobacco mosaic virus, TMV, Tomato mosaic virus, ToMV, cucumber mosaic virus, CMV, Alfalfa mosaic virus, AlMV, Potato virus X (PVX), Potato virus Y (PVY), and Potato leaf roll virus, PLRV. And has more than 100 field trials with more than 20 species. sffdghf Antisense Transgene Coat protein genes have been shown to be effective in preventing or reducing infection and disease caused by homologous and closely related viruses. It was suggested that CP- mediated protection (CPMP) against TMV was through the inhibition of virion disassembly in the initially infected cells. Target viral mRNA Figure 4: Possible mechanisms of antisense gene action. Source: BATS: Centre for Biosafety and Sustainability (www.bats.ch/bats/publikationen/1995-1_TA /3-state.php ) References Antisense mRNA Plant RNAse Andrew O. Jackson Karen-Beth C. Scholthof, Herman B. Scholthof, (1993) and Control of Plant Virus Diseases by Pathogen-Derived Resistance in Transgenic Plants' Plant Physiol. (1993) 102: 7-1 2. Meng. B. and Gubba, A. 2000. Genetic Engineering: A novel and powerful tools to combat plant virus diseases. APSnet Features. Online. doi: 10.1094/APSnetFeature-2000-0500B. Duplex Viral/antisense mRNA Degradation of RNA duplex Binding of Ribosomes inhibited Plant Ribosomes