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. 2009 Dec 1;106(51):22002–22007. doi: 10.1073/pnas.0910811106

Fig. 3.

Fig. 3.

Simulation and experimental validation of the effect of F-actin on ROP1 activity oscillation. (A and B) Simulation of ROP1 activity oscillation in control pollen tubes using model I (A) and model II (B). (C) Experimental measurement of ROP1 activity oscillation in control pollen tubes. The distribution of GFP-RIC4ΔC to the apical PM indicates the apical ROP1 activity (1). Relative ROP1 activity was determined as the ratio of mean PM GFP intensity to mean cytosolic GFP intensity (1). Shown is a typical oscillating pollen tube with an amplitude of 0.5 (from 0.9 to 1.4) and a period of ≈80 s. Six out of 10 pollen tubes exhibited this oscillation pattern. (D and E) Simulations predicted that the apical ROP1 activity would be maintained at very low levels and would not oscillate in pollen tubes treated with 5 nM latrunculin B (Lat B). For model I, k = 3. For model II, k = 1.3. (F) Experimental validation of the predictions in (D) and (E). In tubes treated with 5 nM Lat B, GFP-RIC4ΔC was depleted from the apical PM, and the relative ROP1 activity was consistently below 0.8. Shown is a representative of 30 tubes examined, all of which exhibited low and nonoscillating ROP1 activity. (G and H) Simulations predicted that the relative ROP1 activity would remain high and lose oscillation in pollen tubes treated with 100 nM jasplakinolide (JAS). Under this condition, F-actin is maintained at a high level. For model I, g(x,y) = 0.25. For model II, g(x) = 0.44. (I) Experimental validation of the predictions in (G) and (H). The relative ROP1 activity remained above 1.3. Shown is a representative of 20 tubes examined, all of which demonstrated high and nonoscillating ROP1 activity. (J) Representative snapshot images of GFP-RIC4ΔC localization in control, Lat B–treated, and JAS-treated pollen tubes. (Scale bar: 10 μm.) (K) Quantitative analysis of the relative ROP1 activity in control, Lat B–treated, and JAS-treated pollen tubes. Shown are mean relative ROP1 activity measured from snapshot images (n = 20; P < .05, Student t-test). Error bars indicate SD.