Salt-stress-induced association of phosphatidylinositol-4,5-bisphosphate with clathrin-coated vesicles in plants
Citable Link (URL):http://resolver.sub.uni-goettingen.de/purl?gs-1/5701
Plants exposed to hyperosmotic stress undergo changes in membrane dynamics and lipid composition to maintain cellular integrity and avoid membrane leakage. Various plant species respond to hyperosmotic stress with transient increases in phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2), however, the physiological role of such increases is unresolved. Here, the spatio-temporal dynamics of stress-induced changes in phosphoinositides (PIs) were analyzed in subcellular fractions of Arabidopsis leaves to delineate possible physiological roles. Unlabeled lipids were separated by thin-layer-chromatography and quantified according to gas-chromatographic detection of associated fatty acids. The plasma membrane represents the outermost barrier between the symplast of plant cells and its apoplastic surroundings. Transient PtdIns(4,5)P2 increases upon hyperosmotic stress were detected first in enriched plasma membrane fractions, however, at later time points PtdIns(4,5)P2 increased in endomembrane-fractions of the corresponding two-phase systems. When major endomembranes were enriched from rosette leaves prior to hyperosmotic stress and over 60 min of stimulation, no stress-induced increases in the levels of PtdIns(4,5)P2 were found in fractions enriched for endoplasmic reticulum, nuclei, or plastidial membranes. Instead, increased PtdIns(4,5)P2 contents were found in clathrin-coated vesicles (CCVs), which proliferated several-fold in mass within 60 min of hyperosmotic stress according to the abundance of CCV-associated proteins and lipids. Monitoring the subcellular distribution of fluorescence-tagged reporters for clathrin and PtdIns(4,5)P2 during transient coexpression in onion epidermal cells indicates rapid stress-induced colocalization of clathrin with PtdIns(4,5)P2 at the plasma membrane. The data indicate that PtdIns(4,5)P2 may act in stress-induced formation of CCVs in plant cells, highlighting evolutionary conservation of the PI system between organismic kingdoms.