Figure 1.

Characterization of the phr1 mutant alleles. (A) Histochemical analysis of GUS activity driven by the AtIPS1∷GUS reporter gene in response to phosphate starvation in wild type (wt; left) and in the phr1-1 mutant (right). Scale bar, 1 cm. (B) Histograms of metabolic (anthocyanin and Pi content) and developmental (root/shoot growth ratio and total weight) parameters of the wild-type (wt) and phr1-1 (1-1) and phr1-2 (1-2) mutant alleles, grown under different nutrient regimes; complete medium (+P), Pi starvation (−P), or nitrogen starvation (−N) regimes. (C) Plates containing the wild-type (bottom) and the phr1-1 (left) and phr1-2 (right) mutant alleles grown on different nutrient regimes. Scale bars, 1 cm. (D) Detail showing root hairs of wild type and phr1-1 grown under Pi starvation conditions. Scale bar, 0.5 mm. The analyses were conducted on plants grown in complete medium for 5 d, then transferred to complete medium or to medium lacking Pi or N for 7 d, except in the cases of the Pi and N starvation shown in C, in which the starvation lasted for 12 d. Data represent means of at least six independent measurements. Standard deviations are indicated by bars. Statistically significant differences using the Student's t test between wild-type and phr1 alleles were observed for anthocyanin accumulation, root-to-shoot growth ratio, and total weight for plants grown under Pi starvation conditions (P < 0.01), as well as for total Pi content for plants grown under Pi sufficient conditions (P < 0.02).