An efficient system for plastid transformation in an edible medicinal herb

Transplastomic technology has found diverse applications in metabolic and resistance engineering, yet its implementation has been primarily limited to select plant species like Nicotiana tabacum. Here we report a robust and reproducible plastid transformation system tailored for Solanum nigrum (black nightshade), a significant vegetable and medicine plant within Solanaceous family. A S. nigrum-specific plastid vector, strategically designed for integration between the trnfM and trnG genes of the plastid genome, harbored the spectinomycin-resistance gene (aadA) as a selectable marker and green fluorescent protein (gfp) as a reporter gene. The vector was delivered via biolistic bombardment into leaf explants of S. nigrum, achieving an overall efficiency of approximately fifteen transplastomic events per shot. The site-specific integration of foreign genes and the establishment of a high homoplastomic state were verified through PCR assays and Southern blot analyses. Confocal laser scanning microscopy confirmed the presence of GFP fluorescence in chloroplasts, with GFP accumulation reaching about 2% of the total soluble protein in leaves. Crossing experiments between transplastomic plants and wild-type plants demonstrated the maternal inheritance of the S. nigrum plastid genome. The successful establishment of S. nigrum transplastomic technology holds promise for fostering novel synthetic biology applications within medicinal plant research.