Coexpression of potato PVYo coat protein and cryV-Bt genes in potato.
The codon-modified cryV-Bt gene (cryV-Bt) from Bacillus thuringiensis subsp. kurstaki, which is specifically toxic to Lepidoptera and Coleoptera insects, and a potato Y potyvirus Yo coat protein gene (PVYocp), in which the aphid transmission site was inactivated, were cotransformed into potato (Solanum tuberosum) cv. Spunta via Agrobacterium tumefaciens. The integration and expression of both genes was demonstrated by molecular analysis and bioassays. All cryV-Bt/PVYocp-transgenic lines were more resistant to potato tuber moth (Phthorimaea operculella) and PVYo infection than nontransgenic Spunta. Four cryV-Bt/PVYocp transgenic lines were equal in potato tuber moth mortality to a cryV-Bt transgenic line, but of these four only two lines were equivalent in PVYo titre levels to a PVYocp-transgenic line. Two transgenic lines, 6a-3 and 6a-5, were identified which showed greater resistance to potato tuber moth and PVYo than the other cryV-Bt/PVYocp transgenic lines. This study indicated that multiple genes, conferring insect pest resistance and virus resistance, could be engineered into and expressed simultaneously in a potato cultivar.