Generation of homoplasmic plastid transformants of a commercial cultivar of potato (Solanum tuberosum L.)

This report describes the integration and expression of foreign genes into the plastid genome of a commercial cultivar of potato. Plastid transformation of potato was achieved using two tobacco specific plastid transformation vectors, pZS197 (Prrn/aadA/psbA3′) and pMSK18 (trc/gfp/Prrn/aadA/psbA3′). Selection was for spectinomycin resistance after biolistic delivery of plasmid DNA into leaf cells of Solanum tuberosum cv. Desiree. Ten transplastomic lines were obtained from 179 bombarded samples with vector pZS197 and four transplastomic lines selected out of 103 bombarded samples with vector pMSK18. Southern blot and PCR analyses confirmed homoplasmy in the primary regenerants, and incorporation of the aadA and gfp genes into the potato plastid genome by two homologous recombination events via the flanking plastid DNA sequences. Fluorometric measurements confirmed GFP expression in leaves and tubers of pMSK18 lines. No transformants were obtained with a third tobacco vector, pNtcZ7 (Prrn/gfp/psbA3′/trc/aadA/rrnB-ter) in which the selectable marker gene is driven by a bacterial (trc) promoter, which does permit selection of plastid transformants in tobacco, and allows low level expression of the reporter gene, gfp, in potato.