Auxin Modulates PI Levels at the PM.
(A) Total PI amounts measured in 5-d-old seedlings of the wild type and pip5k mutants before and after treatment with 10 μM NAA for 30 min. Auxin reduced the PtdIns(4,5)P2 levels, indicated here by a 28% reduction in the PtdIns4P:PtdIns(4,5)P2 ratio in the wild type (see Supplemental Figure 10 for specific data). The single and double pip5k mutants failed to respond to auxin by increasing the amounts of PIs. A two-tailed Student’s t test was used; *P < 0.05.
(B) Quantification of the effect of auxin on PtdIns(4,5)P2 and PtdIns4P at the PM as visualized by the PI markers p35S:YFP-PHPLCδ1 and p35S:YFP-PHFAPP1, respectively. A two-tailed Student’s t test was used; *P < 0.05, **P < 0.01. See Methods for details.