title: Combined Activity of DCL2 and DCL3 Is Crucial in the Defense against Potato Spindle Tuber Viroid.
abstract: Viroids are self replicating non-coding RNAs capable of infecting a wide range of plant hosts. They do not encode any proteins, thus the mechanism by which they escape plant defenses remains unclear. RNAi silencing is a major defense mechanism against virus infections, with the four DCL proteins being principal components of the pathway. We have used Nicotiana benthamiana as a model to study Potato spindle tuber viroid infection. This viroid is a member of the Pospiviroidae family and replicates in the nucleus via an asymmetric rolling circle mechanism. We have created knock-down plants for all four DCL genes and their combinations. Previously, we showed that DCL4 has a positive effect on PSTVd infectivity since viroid levels drop when DCL4 is suppressed. Here, we show that PSTVd levels remain decreased throughout infection in DCL4 knockdown plants, and that simultaneous knockdown of DCL1, DCL2 or DCL3 together with DCL4 cannot reverse this effect. Through infection of plants suppressed for multiple DCLs we further show that a combined suppression of DCL2 and DCL3 has a major effect in succumbing plant antiviral defense. Based on our results, we further suggest that Pospoviroids may have evolved to be primarily processed by DCL4 as it seems to be a DCL protein with less detrimental effects on viroid infectivity. These findings pave the way to delineate the complexity of the relationship between viroids and plant RNA silencing response.
authors.affiliation: Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece.
authors.forename: Konstantina
authors.initials: K
authors.lastname: Katsarou
authors.affiliation: Department of Biology, University of Crete, Heraklion, Greece.
authors.forename: Eleni
authors.initials: E
authors.lastname: Mavrothalassiti
authors.affiliation: Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Belgium.
authors.forename: Wannes
authors.initials: W
authors.lastname: Dermauw
authors.affiliation: Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Belgium.|Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, The Netherlands.
authors.forename: Thomas
authors.initials: T
authors.lastname: Van Leeuwen
authors.affiliation: Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece.|Department of Biology, University of Crete, Heraklion, Greece.
authors.forename: Kriton
authors.initials: K
authors.lastname: Kalantidis
mesh_terms: D015152:Blotting, Northern; D020411:Oligonucleotide Array Sequence Analysis; D010935:Plant Diseases / Q000276:immunology* / Q000821:virology; D010940:Plant Proteins / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D014026:Nicotiana / Q000821:virology*; D014772:Viroids / Q000276:immunology* / Q000378:metabolism; D014777:Virus Diseases / Q000276:immunology*
chemical_list: D010940:Plant Proteins