Characterization of a defective RNA derived from RNA 3 of the Y strain of cucumber mosaic virus

A defective (D) RNA 3 naturally generated from the Y strain of cucumber mosaic virus (CMV-Y) was characterized using a biologically active cDNA clone. Sequencing of the clone revealed that the D RNA 3, named D RNA 3Yα, was derived from CMV-Y RNA 3 and contained a 10 nt deletion in the 5′ untranslated region and a 162 nt deletion within the 3a open reading frame. Co-inoculation of D RNA 3Yα with CMV-Y derived from in vitro transcripts facilitated propagation of CMV-Y containing D RNA 3Yα in Nicotiana benthamiana or Nicotiana tabacum plants. CMV-Y, however, did not produce deletion mutants upon serial mechanical passages in the plants.