Abstract
The amyloplast sedimentation to the direction of gravity is important for gravity perception in the endodermal cell during shoot gravitropism. To elucidate the mechanism of gravity perception, we have analyzed the sgr9 (shoot gravitropism9) mutant that exhibits weak gravitropism. We have reported that sgr9 exhibits abnormal amyloplast movement, and SGR9 is likely to be localized to amyloplasts. These results suggested that SGR9 is involved in the regulation of amyloplast sedimentation. It has been suggested that actin filaments (F-actin) is involved in amyloplast sedimentation. To analyze the relationship between SGR9 and F-actin, we observed F-actin surrounding amyloplasts both in wild-type and in sgr9. Amyloplast surrounded by F-actin was more freaquently observed in sgr9 than in wild-type. In addition, inhibition of actin polymerization restored gravitropism and amyloplast sedimentation in sgr9. These results suggest that SGR9 might be involved in the modulation of amyloplast-actin interaction on amylopalsts.
