Fig. S2.

In situ analysis of the PIN1 phosphosite-specificity. Representative confocal images of stele cells of the primary root after immunostaining of 4-d-old wild-type seedlings or pin1 mutant seedlings transformed with PIN1:GFP or PIN1:YFP transgenes with alanine replacement mutations of S1–S4. Seedlings were genotyped for homozygosity of the underlying pin1 mutant allele (pin1^−/−) and stained with anti-GFP (a-GFP, PIN1:GFP; green) and a-PIN1 S1-P (magenta; A), a-PIN1 S2-P (magenta; B), a-PIN1 S4-P (magenta; C), and a-PIN1 S3-P (magenta; D) antibodies. Overlap of green and magenta signals is indicated by white arrowheads in the merged images. Green arrowheads indicate the absence of a corresponding magenta signal from phosphosite-specific antibody staining. (Scale bar, 5 µm.)