Expression of a chimeric nitrate reductase gene in transgenic lettuce reduces nitrate in leaves

Transgenic plants of four glasshouse-grown lettuce cultivars ('Cortina', 'E vola', 'Flora' and 'Luxor') were obtained by co-cultivating excised cotyled ons with Agrobacterium tumefaciens. The Agrobacterium strain LBA4404 contai ned the binary vector pBCSL16, which carried a nitrate reductase (nia) cDNA linked to CaMV promoter and terminator sequences, and the neomycin phospho transferase II (nptII) gene. Transformed shoots were selected by their abil ity to root on medium containing kanamycin sulphate, by a positive NPTII as say and by PCR analysis. The presence of the nia cDNA in transgenic lettuce was confirmed by nitrate reductase (NR) enzymatic assay, a reduction in th e nitrate content of leaves and by Southern hybridisation. PCR analysis of cDNA fragments from transgenic plants confirmed that both nia and nptII gen es were expressed in first seed-generation (T1) lettuce plants. The commerc ial importance of reduced nitrate concentrations in lettuce is discussed.