EXPRESSION OF THE C-4 ME1 GENE FROM FLAVERIA-BIDENTIS REQUIRES AN INTERACTION BETWEEN 5'-SEQUENCE AND 3'-SEQUENCE

The efficient functioning of C-4 photosynthesis requires the strict co mpartmentation of a suite of enzymes in either mesophyll or bundle she ath cells. To determine the mechanism controlling bundle sheath cell-s pecific expression of the NADP-malic enzyme, we made a set of chimeric constructs using the 5' and 3' regions of the Flaveria bidentis Me1 g ene fused to the beta-glucuronidase gusA reporter gene. The pattern of GUS activity in stably transformed F. bidentis plants was analyzed by histochemical and cell separation techniques. We conclude that the 5' region of Me1 determines bundle sheath specificity, whereas the 3' re gion contains an apparent enhancer-like element that confers high-leve l expression in leaves. The interaction of 5' and 3' sequences was dep endent on factors that ape present in the C-4 plant but not found in t obacco.