Abstract
Viruses are obligate parasites which cause a range of severe plant diseases that affect farm productivity around the world, resulting in immense annual losses of yield. Therefore, control of viral pathogens continues to be an agronomic and scientific challenge requiring innovative and ground-breaking strategies to meet the demands of a growing world population. Over the last decade, RNA silencing has been employed to develop plants with an improved resistance to biotic stresses based on their function to provide protection from invasion by foreign nucleic acids, such as viruses. This natural phenomenon can be exploited to control agronomically relevant plant diseases. Recent evidence argues that this biotechnological method, called host-induced gene silencing, is effective against sucking insects, nematodes, and pathogenic fungi, as well as bacteria and viruses on their plant hosts. Here, we review recent studies which reveal the enormous potential that RNA-silencing strategies hold for providing an environmentally friendly mechanism to protect crop plants from viral diseases.
Highlights
Antiviral Plant Defence ResponsesPlant viruses are submicroscopic spherical, rod-shaped or filamentous particles which contain different kinds of genomes
We have demonstrated that transgenic Arabidopsis and barley (Hordeum vulgare) plants, expressing a 791 nucleotide double-stranded RNA (dsRNA) (CYP3RNA) targeting all three CYP51 genes (FgCYP51A, FgCYP51B, FgCYP51C) in Fusarium graminearum (Fg), inhibited fungal infection via host-induced gene silencing (HIGS) [81,82]
The same authors addressed the question whether multiple transgene copies coincided with the processing of hpRNA to siRNA and the occurrence of resistant phenotypes [167]. They found no significant correlation between the resistance and the copy number of the transgene and consistent with another study [94]; structural characteristics of the RNA-silencing construct [148,149], the locus of transgene integration [168,169] and the promotor used for transgene expression [170] as well as undesired transgene silencing provoked by using transgenic technologies [171] may account for RNA-silencing effectiveness
Summary
Plant viruses are submicroscopic spherical, rod-shaped or filamentous particles which contain different kinds of genomes. The controversy on whether plant viruses are recognized as PAMP-coding pathogens is still a matter of debate; recent findings indicate that the detection of dsRNAs (produced as result of virus replication during infection) as viral PAMPs involves typical PTI components, and the induced immune response differs from those of the RNA-silencing pathway [27,28,29,30,31]. Viral effectors are sensed by host R-proteins that trigger a cascade of downstream signalling events that induce R-gene mediated resistance (ETI) How those defences and counter-defences orchestrate in plant-virus interactions is not in the scope of this review, and readers are referred to recent reviews [10,11,12,13,32,33]
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