Transformation of Cowpea Vigna unguiculata with a Full-Length DNA Copy of Cowpea Mosaic Virus M-RNA

A full-length DNA copy of the M-RNA of cowpea mosaic virus (CPMV), supplied with either the 35S promoter from cauliflower mosaic virus (CaMV) or the nopaline synthase promoter from Agrobacterium tumefaciens, was introduced into the T-DNA region of a Ti-plasmid-derived gene vector and transferred to cowpea Vigna unguiculata cells. Southern blot analysis of the transformed callus tissue obtained confirmed the integration of the viral DNA copy into the plant DNA. Northern blot analysis revealed that full-length transcripts of more than 3500 nucleotides long were produced from the integrated copy supplied with either promoter, the CaMV 35S promoter being approx. 10-fold more active than the nopaline synthase promoter. The production of full-length M-RNA-like transcripts in transformed cowpea calli will permit to study M-RNA-expression in the absence of B-RNA and the infectivity of cloned viral DNA copies.