Expression of PVX coat protein gene under the control of extensin-gene promoter confers virus resistance on transgenic potato plants

Tuber discs of potato (Solanum tuberosum L.) cultivars Desirée and Gracia were infected by Agrobacterium tumefaciens carrying a binary vector with the coat protein gene of potato virus X controlled by the carrot extensin gene long-transcript promoter. Several transgenic potato plants have been obtained by direct regeneration of shoots on culture medium with kanamycin used for selection. The presence of the coat protein gene was proved by Southern hybridization in several transformants. Its low but detectable expression level was shown by Northern and Western analysis. Ethephon treatment resulted in a five-fold increase in the amounts of the coat protein mRNA. The majority of transformants exhibited reduced accumulation of virus RNA in inoculated leaves. Potentials in the use of an ethylene-inducible promoter in the production of virus-resistant transgenic plants will be discussed.