Symptomless infectious cDNA clone of a Norwegian isolate of Poinsettia mosaic virus.

An infectious cDNA clone of a Norwegian isolate of Poinsettia mosaic virus (PnMV) was generated. It consisted of 6,098 nucleotides and encoded a polyprotein of 219.5 kDa. Sequence comparisons indicated that this isolate shared 98.6% (nucleotide) and 97.1% (amino acid) identity with the previously sequenced isolate from Germany. RNA transcripts derived from this cDNA were infectious in Nicotiana benthamiana. However, plants did not present typical PnMV symptoms. Furthermore, RNA transcripts from this cDNA clone were not infectious in poinsettia. Serial propagation of this cDNA clone in N. benthamiana plants restored symptom induction in this host but did not re-establish infectivity in poinsettia.