Figure 2.

Spm‐induced PIP₂ is triggered by activation of PIP5K, not through inhibition of PLC or PIP₂ phosphatase.

(a) Seedlings were pulse‐labelled with ³²P_i for 15 min and then treated with Spm or buffer alone (Ctrl) for the times indicated. The PIP₂ fold increase of two independent experiments is shown (squares and triangles). (b) Pulse‐chase experiment where seedlings were treated with buffer ± Spm for 15 or 30 min (triangles and squares, respectively), labelled with ³²P_i for 5 min and then chased (t = 0) with non‐radioactive P_i in the presence or absence of Spm for the times indicated. Values in (a) and (b) were normalised to ³²P‐PI and expressed with respect to Ctrl, 0 min. Open symbols, Ctrl; closed symbols, Spm. (c) ³²P‐PIP₂ response to Spm of WT and pip5k7, pip5k9 and pip5k7 pip5k9 (pip5k7/9) double mutants. Seedlings were ³²P_i‐labelled overnight and treated for 30 min with 60 μm Spm. (d) ³²P‐PA response in WT and pip5k7/9 mutant plans. Data show that the PA response is independent of PIP₂. In all cases, data are presented as the mean ± SD (n = 3).