Strigolactone Can Promote or Inhibit Shoot Branching by Triggering Rapid Depletion of the Auxin Efflux Protein PIN1 from the Plasma Membrane
Figure 5
Characterisation of strigolactone-induced PIN1 protein instability in inflorescence stems.
(A) Effect of the vesicle trafficking inhibitor brefeldin A (BFA) on PIN1 protein. (B) Lack of recovery of PIN1 signal after photobleaching. (C) Effect of the clathrin-dependent endocytosis inhibitor A23 on GR24-induced instability of PIN1 protein. (D) Effect of GR24 on stability of a PM-localised protein other than PIN1. In (A–C), the GFP signal in longitudinal sections from inflorescence stems of 6-wk-old soil-grown plants harbouring PIN1:PIN1–GFP was monitored up to 180 min after mounting with 50 µM BFA for (A), before and up to 180 min after photobleaching for (B), or up to 90 min after mounting prior to 30-min pretreatment of 50 µM A23 or its inactive analogue A51 before addition of the vehicle control or 5 µM GR24 (indicated by the arrow) for (C); means ± s.e.m. of the basal PM region of 5–9 cells are shown as a percentage to the value just after mounting; comparison was performed between samples just after mounting and either 60, 120, or 180 min after mounting by one-tailed paired t test for (A), between samples 10 min and 90 min after photobleaching by one-tailed paired t test for (B), or between the vehicle control and GR24-treated samples by one-tailed Student's test at each time point for (C). In micrographs of (A) and (B), green shows the PIN1–GFP signal, and magenta shows autofluorescence of chloroplasts; scale bar: 20 µm; an arrowhead indicates PIN1-rich compartment in (A), or a bleached region of the basal PM in (B). In (D) the YFP signal in longitudinal sections from inflorescence stems of 6-wk-old soil-grown plants harbouring UBQ10:PIP1–YFP, which encodes a fluorescence-tagged aquaporin protein, was monitored up to 90 min after mounting with the vehicle control or 5 µM GR24; means ± s.e.m. of the basal PM region of seven cells are shown as a percentage of the value just after mounting; the vehicle control versus GR24-treated samples were compared by Student's test at each time point. Results presented are typical of at least two independent experiments.