AtMRP6 gene expression determined by RT-Q-PCR and promoter GUS analysis. (A) Quantification of AtMRP6 expression level by real-time quantitative PCR using mRNA extracted from various tissues or developmental stages. Values from three independent experiments are expressed relatively to actin-2 gene levels. (B-F) Activity of the uidA reporter gene in transgenic Arabidopsis plants expressing pAtMRP6-GUS fusion at different stages of development : germinated seeds after 24-hr (B), seedling with closed cotyledons after 48-hr (C), seedlings showing the apical meristem (D), emergence of a secondary root (E), root radial section (F). (Scale bar corresponds to 0.5 mm in B and C, 0.5 cm in D, 0.2 mm in E and 50 μm in F).