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Effects of the myosin ATPase inhibitor 2,3‐butanedione monoxime on amyloplast kinetics and gravitropism of Arabidopsis hypocotyls
Author(s) -
Palmieri Maria,
Schwind Melissa A.,
Stevens Martin Henry H.,
Edelmann Richard E.,
Kiss John Z.
Publication year - 2007
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.2007.00926.x
Subject(s) - amyloplast , gravitropism , endodermis , clinostat , microbiology and biotechnology , biophysics , hypocotyl , biology , plasmodesma , arabidopsis , botany , biochemistry , plastid , chloroplast , gene , mutant , cytoplasm
The actin cytoskeleton is a crucial component in plant gravitropism, and studies confirm that alterations to actin filaments (F‐actin) can have dramatic effects on gravitropic curvature in roots and shoots. Many models for gravisensing in higher plants suggest that the key to gravity perception and signal transduction lies in intimate interactions between F‐actin and amyloplasts. In this study, we investigated gravitropism in hypocotyls by analyzing the effect of myosin inhibition on gravitropic curvature in order to clarify the role of the actomyosin system in shoot gravitropism. To study amyloplast movement in endodermal cells (i.e., gravity‐perceiving statocytes) of living seedlings, we repositioned a confocal laser scanning microscope (CLSM) so that its rotatable stage was oriented vertically. Seedlings containing green fluorescent protein‐labeled endodermal amyloplasts were incubated with the ATPase inhibitor 2,3‐butanedione monoxime (BDM) and then mounted on the stage so that the hypocotyls were vertical. Using CLSM, we imaged the endodermal amyloplasts, while the hypocotyls were oriented vertically and also after they were reoriented by 90°. Our results show that BDM reduces gravitropic curvature in a concentration‐dependent manner. In addition, BDM increases amyloplast movement in hypocotyls of vertical seedlings, but reduces amyloplast movement in hypocotyls of reoriented seedlings, suggesting that myosin may participate in the intracellular transport of amyloplasts in statocytes. These results can be explained in the context of amyloplasts as both noise indicators and gravity susceptors, with BDM producing less coherent amyloplast movement that results in an increased signal‐to‐noise ratio, which may account for at least part of the observed reduction in gravitopic curvature.