Fig. 4

Expression of tobacco ZIP genes in the apical, middle and basal parts of roots from plants grown under various Zn and Cd concentrations. 3.5-week old plants grown in the quarter-strength Knop’s medium were exposed to the control medium supplemented with pairwise combinations of Zn (0; 1 μM) and Cd (0; 0.25; 1 μM) for 17 days. ZIP genes preferentially expressed in the apical root part (a): NtZIP2 (a1), NtZIP5A (a2), NtZIP5B (a3), NtIRT1 (a4), NtIRT1-like (a5); in the basal root part (b): NtZIP1-like (b1), NtZIP8 (b2); equally expressed in tested three root parts (c): NtZIP4A (c1), NtZIP4B (c2); mixed expression pattern for tested three root parts (d): NtZIP5-like (d1), NtZIP11 (d2). Gene expression was normalized to the PP2A level. Values correspond to arithmetic means ±SD (n = 3); those with the ratio greater than 2 are considered significantly different