Fig. 1

Infectivity of the infectious cDNA clone of SCMV in maize plants. a Schematic representation of the infectious clone of SCMV. The full-length cDNA of SCMV was engineered into a binary vector pCB301 between the double CaMV 35S Promoter (2 × 35S) and the Nos Terminator (NOS). SCMV viral genome contains a long open reading frame (ORF) coding for a single major polyprotein that is proteolytically processed by three viral-encoded proteinases to form ten mature proteins: P1, HC-Pro, P3, 6K1, CI, 6K2, VPg, NIa-Pro, Nib, and CP. The small box below the large ORF indicates the pipo ORF, the product of which is expressed as a fusion with the N-terminal of P3. A₆₀ indicates the poly(A) tail. b Illustration of the procedure for virus inoculation of maize plants with SCMV-based vectors. c Viral infection symptoms in upper systemically infected leaves of maize plants inoculated with leaf sap from pSCMV-infiltrated N. benthamiana. At 4 dpi, SCMV induced yellowish spots or streaks in the young leaves, whereas mock-inoculated leaves showed no symptoms. d Detection of SCMV RNA in the systemically infected leaves of maize. Total RNA was extracted from upper uninoculated leaves and subjected to RT-PCR analysis. Levels of EF1a transcripts in these tissues were used as an internal control