Figure 6.

PIN2 response to both salt and gravity stimulations. A and B, Reverse transcription-PCR analysis of mRNA abundance of PIN2 in response to salt stress. Five-day-old Col-0 (A) and sos1-1 (B) seedlings were treated with 150 mm and 100 mm NaCl, respectively. RNA was extracted from the treated roots on the indicated time after salt treatment. Abundance of ACT2 mRNA gene was used as loading control. The data are from a single experiment and are representative of two replicates. C, Expression and localization of PIN2 in the reoriented primary roots at specified time points. Five-day-old Arabidopsis seedlings expressing the PIN2∷PIN2:GFP germinated on MS medium were transferred to the media containing 0 or 150 mm NaCl with 90° horizontal reorientation. GFP signals were visualized by a confocal microscope. Bar = 100 μm. D, Close-up observation of epidermis and cortex cells revealed basipetal localization and expression and diffusion of PIN2 in control seedlings or with 150 mm NaCl at 8 h after treatments. Bar = 100 μm. E, Quantification of GFP fluorescence intensity in root tip cells. n = 10 for each experiment, repeated in triplicate. Statistical analysis indicates significant differences (*, P < 0.05; **, P < 0.01) compared with the control using one-tailed Student's t test. [See online article for color version of this figure.]