Fig. 8.

Lateral root primordium-specific activity of the VvK5.1 promoter. Tissue-specific activity of the VvK5.1 promoter was investigated by histochemical analysis of GUS staining (blue colour) in transgenic Arabidopsis seedlings expressing GUS under control of the VvK5.1 promoter region. This activity was observed in 6- (A) and 10-day- (B–G) old seedlings grown in vitro in a growth chamber (16 h light photoperiod, 140 μM photons m⁻² s⁻¹, 21 °C ,and 70% humidity during both light and darkness) on half-strength Murashige and Skoog (MS/2) medium, supplemented with hygromycin (25 mg l⁻¹). (A) A full view of the whole plantlet. Lateral primordia locations are indicated by arrows. (B–G) A coordinated cell division programme produces the root primordium, shown from the two-cell stage (B) to the stage where the lateral root primordium emerges at the root surface (G). Note that in each stage of the cell division programme, an intense blue colour is present within the most central cells of the primordium, which are known to undergo further cell divisions. In the stages where the primordium emerges at the root surface (F and G), the most intense blue colour is located within the root apex and the root cap.