STUDIES ON SYNERGISM AND COMPLEMENTATION OF LONG DISTANCE MOVEMENT OF CYMBIDIUM MOSAIC VIRUS RNA BY ODONTOGLOSSUM RINGSPOT VIRUS COAT PROTEIN

Abstract

There are two common orchid viruses, namely Cymbidium mosaic virus (CymMV) and Odontoglossum ringspot virus (ORSV). Complementation of movement and coat proteins of these two orchid viruses was studied. We produced four transgenic lines, each harboring one of the movement protein (MP) or coat protein (CP) genes of CymMV or ORSV. The MP of CymMV consists of three overlapping open reading frames (ORFs) called the triple gene block (TGB). We also generated CymMV and ORSV mutants each carrying an inactivated MP or CP. Complementation was studied by infecting transgenic plants with in vitro transcripts generated from these mutants. The cell-to-cell movement of a movement-deficient CymMV could be restored in transgenic plants carrying the ORSV MP transgene. Similarly, CymMV TGB123 transgenic plants were able to rescue the cell-to-cell movement of a movement-deficient ORSV mutant. ORSV CP transgenic plants were able to support systemic movement of a CymMV CP-deficient mutant. Trans-encapsidation was not observed. The complementation of MPs and CPs of CymMV and ORSV facilitates movement of the two viruses in plants, with an exception in long distance movement of ORSV RNA by CymMV CP. The synergism between CymMV and ORSV was examined using viral RNA and CP accumulation in single and double infections.