Figure 3.

Split-root assays of systemic repression of Pi-starvation responses in ahk mutants. A, Schema of the split root experiment. First plants were grown for 10 d in complete medium and then transferred for an additional 2 d to a Pi-lacking medium. Subsequently, plants were transferred for 1 or 2 d to split plates with two independent compartments placing part of the root system in each of these compartments. B, Northern analysis of systemic repression of Pi-starvation response in the cre1 ahk3 double mutant. Plants were grown for 1 or 2 d with the roots split in two compartments having Pi-sufficient (P1/2) media and Pi-lacking media (−P1/2), respectively. As control, both parts of the split root system were placed in Pi-rich media (+). In this experiment, only wild-type (wt) and double mutant cre1 ahk3 RNA were prepared from each part of the split root harvested independently when they where placed in different media, and 10 μg of RNA sample were used in the experiment. The blot was hybridized with the probes corresponding to the Pi starvation-responsive genes indicated.