DIFFERENTIAL EXPRESSION OF A GAMMA-ZEIN GENE IN MEDICAGO-SATIVA, LOTUS-CORNICULATUS AND NICOTIANA-TABACUM

With the aim of increasing the content of sulphur amino acids (SAAs) i n the aerial part of the plants, Nicotiana tabacum and two leguminous species, Medicago sativa and Lotus corniculatus, were transformed with a maize gamma-zein gene (G1L), coding for a SAAs-rich protein. Gene f usions with two different promoters were constructed; one promoter was the constitutive cauliflower mosaic virus (CaMV) 35S and the other wa s the light-regulated ribulose bisphosphate carboxylase small subunit (rbcS) from a tobacco gene. The constructs were introduced by Agrobact erium-mediated gene transfer. All the transformants produced the G1L R NA (two differently sized transcripts were detected) and no relevant d ifferences were found between the two promoters. Despite the presence of G1L message the gamma-zein was found only in tobacco plants (up to 0.05% of the alcohol soluble proteins). Post-transcriptional mechanism s seemed to inhibit protein accumulation. The low level of G1L RNA in the transformed plants was probably the main factor that limited the p roduction of gamma-zein protein. (C) 1997 Elsevier Science Ireland Ltd .