RNA REPLICATION OF PLANT-VIRUSES CONTAINING AN RNA GENOME

This chapter discusses the current knowledge of viral RNA replication. It presents both in vivo and in vitro data. The discussion in the chapter is restricted to those viruses for which RdRp complex has been isolated, irrespective of whether the enzyme requires exogenous RNA for its activity, and thus initiates and elongates complementary RNA chains, or whether it still retains RNA molecules (whose synthesis was initiated in vivo), and thus only elongates these RNA chains. RNA replication of viruses with a tripartite RNA genome, such as brome mosaic virus (BMV), cowpea chlorotic mottle virus (CCMV), cucumber mosaic virus (CMV), and alfalfa mosaic virus (AlMV), is described in the chapter, followed by the replication of viruses with a monopartite genome. These include turnip yellow mosaic virus (TYMV) and tobacco mosaic virus (TMV), then cowpea mosaic virus (CPMV) with a bipartite genome. RNA replication of velvet tobacco mottle virus (VTMoV) is last because of the limited information available on the replication mechanism of its RNA. The enzymes isolated from the first five viruses presented (BMV, CCMV, CMV, AIMV, and TYMV) are capable not only of elongating but also of initiating (–)–RNA strand synthesis because they are devoid of endogenous RNA; the RdRp's of the last three viruses (TMV, CPMV, and VTMoV) are only capable of elongating chains whose synthesis has been initiated in vivo. © 1992 Academic Press Inc.