Abstract
Stomata, which consist of pairs of guard cells, open and close in response to environmental changes. Previous studies suggested actin microfilaments (MFs) were involved in the stomatal movements, however, their dynamics and roles are still unknown. In this study, we acquired microscopic images of GFP-ABD2-labelled MFs with diurnal cycle in Arabidopsis guard cells. From the images, we quantitatively estimated the dynamics including their orientation, bundling and density using our original image analysis systems. As a result, it was revealed that transient actin bundling occurred in the process of stomatal opening. We next performed similar analyze using GFP-mTn expression lines. Although GFP-mTn is useful MF-probes, recent studies have shown that they induced excessive bundling. Our results showed that GFP-mTn-labelled MFs were continually bundled in guard cells. Interestingly, stomatal opening is suppressed in GFP-mTn line. These results suggested that transient actin bundling plays important roles in promotion of stomatal opening.
