An inhibitor of virus replication associated with green island tissue of tobacco infected with cucumber mosaic virus

Abstract

A substance(s) which inhibits virus replication (IGI) was released by protoplasts obtained from green island leaf tissue of tobacco, cv. Xanthi-nc, infected with cucumber mosaic virus (CMV). It was also obtained directly from green island leaf tissue. IGI inhibited both CMV and tobacco mosaic virus (TMV) replication in protoplasts and leaf tissue disks, with the degree of inhibition being dependent upon the concentration applied. The IGI was partially purified to yield two active fractions with molecular weights, determined by gel filtration, of about 26 000 and 57 000. They were both degraded by trypsin and chymotrypsin. IGI appears to be very similar to the inhibitor of viral replication (IVR) obtained from hypersensitively responding tissues since they both possess similar serological determinants. Fractions with similar activity were obtained from green island leaf tissue of the tobacco, cv. Samsun, infected with CMV. The inhibitory activity was also associated with two components with molecular weights of about 26 000 and 57 000, but they differed serologically from both the IVR and IGI obtained from Xanthi-nc.