CUCUMBER MOSAIC-VIRUS REPLICATION IN COWPEA PROTOPLASTS - TIME COURSE OF VIRUS, COAT PROTEIN AND RNA-SYNTHESIS

The time course of the synthesis of cucumber mosaic virus (CMV), CMV coat protein and the 4 CMV RNA was followed in cowpea protoplasts. CMV synthesis was estimated by analytical sucrose gradient centrifugation of extracts from protoplasts and by infectivity assay; coat protein synthesis was determined by incorporation of radioactive amino acids and analytical polyacrylamide slab gel electrophoresis, while the synthesis of CMV RNA was determined by hybridization analysis with labeled specific complementary (c)DNA probes. There was a coordinate synthesis of CMV, CMV coat protein and virus RNA up to 50 h p.i. [post-infection] whereas the rate of coat protein synthesis reached a peak at about 15 h p.i. Coat protein was the only virus-induced protein detected. Results on the relative synthesis of RNA 3 and 4 indicated that RNA 4 was derived by nucleolytic cleavage of RNA 3 and not by transcription of a negative RNA 4 strand.