Figure 3.

CKL2 Stabilizes Actin Filaments in Guard Cells.

(A) Actin filament organization in guard cells of Col-0 and ckl2 35Sp:GFP-fABD2-GFP transgenic plants before (right) and after (left) 200 nM LatA treatment for 30 min.

(B) Quantification of the relative average fluorescence pixel density of GFP-fABD2 signal in guard cells as shown in (A). After LatA treatment, Col-0 and ckl2 mutant had lower relative average fluorescence pixel density of GFP-fABD2 signal compared with control (P = 0.0204, 0.0037).

(C) Actin filament organization in guard cells of Col-0 and ckl2 35Sp:GFP-fABD2-GFP transgenic plants before (right) and after (left) 2 μM ABA treatment for 0.5 h.

(D) The extent of filament bundling (skewness) of guard cells shown in (C). The ckl2 mutant had significantly increased average actin filament density compared with Col-0 after ABA treatment (P = 0.0029). The ckl2 mutant had significantly decreased average actin filament density than Col-0 before ABA treatment (P = 0.0056).

(E) Average filament density of Col-0 and ckl2 guard cells before and after 2 μM ABA treatment as shown in (C). ckl2 mutant had significantly decreased average actin filament skewness values compared with Col-0 after ABA treatment (P = 0.0068). No significant difference of average actin filament skewness values between Col-0 and ckl2 mutant was observed before ABA treatment (P = 0.0993).

Values of (B), (D), and (E) represent the means ± sd of three independent experiments; 50 stomata were analyzed per line. The data sets were tested for normal distribution by the Shapiro-Wilk test. Statistical significance was determined by Student’s t test. Significant differences are denoted with asterisks (**P < 0.01 and *P < 0.05) in (B). Significant differences (P < 0.01) are indicated by different lowercase letters in (D) and (E).