The <i>tuf</i> gene family of soybean : structure and differential transcription

The nuclear genome of soybean (<i>Glycine max</i> L.) contains a family of four <i>tuf</i> genes coding for the chloroplast translation elongation factor EF-Tu. Genomic and cDNA sequencing reveal that the four <i>tuf</i> genes belong to two subfamilies (type A and type B). <i>Tuf</i> genes A1/A2 are highly expressed in green organs (leaves and stems) while <i>tuf</i> genes B1/B2 are poorly expressed in leaves and stems. Both types of genes are about equally expressed in roots albeit at a low level. The 5′ flanking regions of <i>tuf</i>A1 and B1 are tested for promoter activities (GUS) in transformed green tobacco. The <i>tuf</i>A1 promoter is much stronger than the B1 promoter. Promoter deletion studies with <i>tuf</i>A1-derived constructs allowed identification of a DNA segment essential for gene transcription.