03-08-2013, 04:17 PM
Post Transcriptional Gene Silencing: a Tool to Develop Virus Disease Resistance
ABSTRACT
Viruses are known to cause extreme damage to the crop plants leading to severe losses in their production. Controls of these viruses have been approached through conventional spraying of chemicals to control vectors and breeding through the use of resistant lines. Genetic engineering to produce virus-resistant plants has played an important role as exemplified through the development of the papaya with resistance to ring spot virus. The strategies of genetic engineering include protein based and RNA based resistance. The expression of the coat protein has been used for development of the resistance but in a number of cases, the resistance has been demonstrated to occur at RNA level. Coat protein (CP) protection has been successful and applied against several RNA viruses. The RNA silencing mechanism is now a powerful tool to develop crops species resistant to viruses. The expressions of virus-derived sense or antisense RNA in transgenic plants conferring RNA-mediated virus resistance appear to induce a form of post-transcriptional gene silencing (PTGS). It’s a nucleotide sequence specific process that induces mRNA degradation. RNA silencing, an evolutionary mechanism protecting cells from pathogenic RNA and DNA, is increasingly viewed as an adaptive immune system of plants against viruses. Several lines of research indicate that RNA silencing is a general antiviral defense mechanism in plants. In plants, RNA silencing can be induced locally and then spread throughout the organisms, and this aspect of the process likely reflects its role in viral defense. Several PTGS constructs are available for transformation and organizing the presentation will focus on various aspects of PTGS with special attention to resistance to tomato leaf curl virus.