Vector. The EB4 coding sequence was amplified from a pCANTAB 5E vector carrying the virus gene using 3 primer pair sets. The resulting PCR products were purified then digested overnight with HindIII restriction endonuclease, with the same treatment carried out on the full-length clone of CGMMV (pCGT7X, ∼9.0 kb) previously constructed [7] . The digested PCR products and the linearized pCGT7X were purified following 1% agarose gel electrophoresis, and then ligated to form pRT, pRG, both containing the TMV read-through sequence [12] and pCG+FSRTRE (containing the CGMMV read-through sequence) [13] , respectively ( Figure 1 ). The three primer sets used in the amplifications were as follows.