Effect of OsZIP9 overexpression on grain yield in rice under field conditions. A, Identification of three transgenic OsZIP9ox lines (OsZIP9ox-1, OsZIP9ox-6, and OsZIP9ox-7) in which the OsZIP9 specific mRNA levels were increased between 40- and 70-fold. B, Phenotypes of wild-type (WT) and OsZIP9ox plants at the grain filling stage. C to G, Plant height (C), tiller number (D), spikelets per panicle (E), percent filled spikelets (F), and 1000-grain weight (G) for the wild type and the OsZIP9ox-1, OsZIP9ox-6, and OsZIP9ox-7 lines. H and J, Concentrations of Zn (H) and Cd (J) in different tissues. I and K, Zn (I) and Cd (K) concentrations in brown rice. Values represent means ± sd of biological replicates (n ≥ 3). Statistical comparison was performed by Tukey’s HSD mean-separation test (*P < 0.05 and **P < 0.01). DW, Dry weight.