Isolation, phenotypic characterization of AtMRP6 knock-out plants and co-regulation of the AtMRP3, 6, 7 genes cluster. (A) Detection of AtMRP6 transcripts in the different T-DNA insertion lines determined by RT-PCR experiments on total RNAs isolated from roots of the different genotypes, using specific primers downstream from the insertions. (As a control, RT-PCR was performed with actin-2 primers.) (B) Growth of wild-type (Col-0), Atmrp6.1, and Atmrp6.2 mutant plants on agar plates, 21 days after germination, in the presence/absence of 1 μM CdSO4 (C) Cadmium sensitivity of Atmrp6.1 and Atmrp6.2 mutant plants measured as the rosette-leaves fresh weight. Bars correspond to the mean (± SEM) of eight agar-plate dishes from four independent experiments. In each agar-plate (with or without cadmium), 15 plants per genotype were analyzed. (D) Comparative expression of AtMRP1, 3, 6 and 7 genes in roots in response to cadmium. Plants were treated with CdSO4 in hydroponic conditions according to times and concentrations given in the caption. mRNAs were extracted and RT-Q-PCR were performed using specific primers for the three different genes of the cluster (AtMRP3, AtMRP6, AtMRP7) and with AtMRP1 (At1g30400) as a control. (C-D) Values from independent experiments are expressed as percentage of control (untreated plants). (** : P < 5e-3, * P < 8e-3, t-test).