title: Post-transcriptional gene silencing suppressor activity of two non-pathogenic alphasatellites associated with a begomovirus.
abstract: Alphasatellites and betasatellites are begomovirus-associated single-stranded circular DNA molecules. Two distinct alphasatellites, Gossypium darwinii symptomless alphasatellite and Gossypium mustelinium symptomless alphasatellite, were previously isolated from Gossypium davidsonii and G.mustelinium. Here we show that the replication-associated proteins (Rep: a rolling-circle replication initiator protein) encoded by these alphasatellites interact with the Rep and C4 proteins encoded by their helper begomovirus, Cotton leaf curl Rajasthan virus (CLCuRaV), in a yeast two-hybrid assay. Both the alphasatellite-encoded Reps were found to have strong gene silencing suppressor activity, in contrast to the betasatellite-encoded betaC1 and CLCuRaV-encoded C2, C4 and V2 proteins. The presence of alphasatellites maintained suppression of gene silencing in the youngest, actively growing tissue of CLCuRaV-betasatellite-infected plants. This is the first demonstration of a rolling-circle replication initiator protein with suppressor of gene silencing activity and provides a possible explanation for the selective advantage provided by the association of alphasatellites with begomovirus-betasatellite complexes.
authors.affiliation: ILTAB, Donald Danforth Plant Science Center, St. Louis, MO 63132, USA.
authors.forename: Muhammad Shah
authors.initials: MS
authors.lastname: Nawaz-Ul-Rehman
authors.forename: Nazia
authors.initials: N
authors.lastname: Nahid
authors.forename: Shahid
authors.initials: S
authors.lastname: Mansoor
authors.forename: Rob W
authors.initials: RW
authors.lastname: Briddon
authors.forename: Claude M
authors.initials: CM
authors.lastname: Fauquet
mesh_terms: D053839:Begomovirus / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004276:DNA, Satellite / Q000235:genetics / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics* / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D003368:Gossypium / Q000235:genetics / Q000821:virology; D010935:Plant Diseases / Q000821:virology; D018515:Plant Leaves / Q000821:virology; D034622:RNA Interference / Q000187:drug effects; D014026:Nicotiana / Q000821:virology; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D004276:DNA, Satellite; D004279:DNA, Viral; D015534:Trans-Activators; D014764:Viral Proteins; C045264:replication initiator protein; D004265:DNA Helicases