Fig. 4

Relative expression levels of miR399a (a and d), miR399d (b and e), and PHO2 (c and f) in leaves (upper panel) and SAM (lower panel) of maize subjected to external sucrose treatments. Sets of 4-fully expanded leaf stage seedlings were then transferred to the Hoagland’s medium containing either 0.25 mM phosphate (P+, Control) or no additional phosphate (P−, LP). One set of the P+ and P− media contained 3% sucrose (S, LP + S), while another set was not supplemented with sucrose (LP). Two days later, plants were harvested. Error bars indicate SDs (n = 3). Significant differences were evaluated using Student’s t-test; *^{, +} P < 0.05, **^{, ++} P < 0.01. ⁺ refers to significant differences between each treatment and the control; *, indicates significant differences between the maize H4 and NIL