Crop Stress and its Management: Perspectives and Strategies
Crops experience an assortment of environmental stresses which include abiotic viz., drought, water logging, salinity, extremes of temperature, high variability in radiation, subtle but perceptible changes in atmospheric gases and biotic viz., insects, bi
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RNAi: Machinery and Role in Pest and Disease Management Surekha Agarwal, Muthugounder Mohan, and Satendra K. Mangrauthia
Abstract RNA interference (RNAi) is a homology-dependent gene silencing technology that is initiated by double stranded RNA (dsRNA). A multitude of small RNAs accumulate in plant tissues, although heterogeneous in size, sequence, genomic distribution, biogenesis, and action, most of these molecules mediate repressive gene regulation through RNA silencing. Micro and small interfering RNAs represent small RNA families that are recognized as critical regulatory species across the eukaryotes. Besides their roles in developmental patterning and maintenance of genome integrity, small RNAs are also integral components of plant responses to adverse environmental conditions, including biotic stress. Recent studies broaden the role of RNAi, and many successful examples have described the application of RNAi for engineering plant resistance against a range of prokaryotic and eukaryotic organisms. Expression of dsRNA directed against suitable pathogen and insect genes in transgenic plants showed protection against pests, opening the way for a new generation of pest and disease resistant crops. Here, current knowledge on the uptake mechanisms of dsRNA in plant pests and the potential of RNAi to control pest and pathogen is described. Concerns regarding further research on dsRNA uptake mechanisms and the promising application possibilities for RNAi in pest and disease management have been discussed. Further, the progress of RNAi-based transgenic plant resistance against eukaryotic pests, as well as future challenges and prospects are addressed.
S. Agarwal • M. Mohan • S.K. Mangrauthia (*) Directorate of Rice Research, Hyderabad 500 030, Andhra Pradesh, India e-mail: [email protected]
B. Venkateswarlu et al. (eds.), Crop Stress and its Management: Perspectives and Strategies, DOI 10.1007/978-94-007-2220-0_13, © Springer Science+Business Media B.V. 2012
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Introduction
RNA interference (RNAi) is a gene silencing phenomenon found in almost all the eukaryotes that inhibits gene expression through homology based sequence-specific interactions. Biochemical and genetic studies have demonstrated that the core mechanisms and machinery of RNA silencing are shared among different organisms. The phenomenon is conserved across kingdoms and is manifested as quelling in fungi, RNAi in animals, and co-suppression or post-transcriptional gene silencing (PTGS) in plants. RNAi is considered as one of the major breakthrough of twenty-first century in molecular biology. It was first discovered in plants and fungi when the over-expression of a gene suppressed the expression of both the endogenous gene and transgene (Napoli et al. 1990). A similar phenomenon in Neurospora crassa was studied, wherein introduction of homologous RNA molecules resulted “quelling” of the endogenous gene (Romano and Macino 1992). In animals, the phenomenon was first reported by Guo and Kemphues (1995) where they found
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