Replicase mediated resistance against Potato Leafroll Virus in potato Desirée plants

Abstract

Potato leafroll virus (PLRV) is a major menace for the potato production all over the world. PLRV is transmitted by aphids, and until now, the only strategy available to control this pest has been to use large amounts of insecticides. Transgenic approaches involving the expression of viral replicases are being developed to provide protection for plants against viral diseases. The purpose of this study was to compare the protection afforded by the differential expression of PLRV replicase transgene in potato plants cv. Desirée. Plants were genetically modified to express the complete sense PLRV replicase gene. Two constructions were used, one containing the constitutive 35SCaMV promoter and the other the phloem-specific RolA promoter from Agrobacterium rhizogenes. Transgenic plants were infected with PLRV in vitro, using infested aphids. In plants in which 35SCaMV controlled the expression of the PLRV replicase gene, signs of infection were initially detected, although most plants later developed a recovery phenotype showing undetectable virus levels 40 days after infection. In turn, those plants with the RolA promoter displayed an initial resistance that was later overcome. Different molecular mechanisms are likely to participate in the response to PLRV infection of these two types of transgenic plants.

Evaluation of genetically modified sugarcane lines carryingCry1AC gene using molecular marker techniques

“…Different authors claimed that the transformation process and the tissue culture may induce mutations that can alter different biological phenomena in the plant. [16][17][18][19][20][21] Transgenic sugarcane plant development via A. tumefaciens mediated transformation is accompanied with partial but visible genomic changes. 16 Carmona et al 16 also pointed out that somaclonal variation resulted in sugarcane transgenic plants developed by preexisting DNA polymorphism into the donor genotype and tissue culture procedure during the transformation experiment.…”

Marker-free PLRV resistant potato mediated by Cre-loxP excision and RNAi

“…The recovery phenotype, typified by initially symptomatic plants recovering from virus infection, is not uncommon among transgenic plants, and it has also previously been observed in PLRV transgenic plants (Ehrenfeld et al 2004). Recovery was not observed in secondary infection, which is concurrent with the notion that infection is always more severe in plants obtained from infected tubers.…”

“…The use of transgenes for expression of plant virus sequences, to induce resistance (pathogen derived resistance), is one means by which the problems of complex inheritance of PLRV resistance can be overcome (Barker and Waterhouse 1999), and there are several reports on the successful application of this technology as well as commercial releases of NewLeaf varieties in the US (Barker et al 1992, 1994; Ehrenfeld et al 2004; Graham et al 1997; Kawchuk et al 1990; Thomas et al 2000). Pathogen-derived resistance activates a natural cytoplasmic antiviral mechanism called RNA interference (RNAi).…”

Small RNA Based Genetic Engineering for Plant Viral Resistance: Application in Crop Protection

“…Phloem tissue is the highway for viral systemic spread within the plants. In a study both phloem-specific promoter and 35S promoter were tested to drive the expression of silencing genes and the 35S promoter driven construct provided better resistance (Ehrenfeld et al, 2004). Expression of virus-targeting small RNA constitutively in all cell types may provide second line of defense in case virus breaks the defense in phloem and evade into newer tissue.…”