Structural sterols are integral components of the plasma membrane. They are enriched in spatially differentiated microdomains, “lipid rafts”. We visualized structural sterols in root apex of Arabidopsis thaliana by fluorescence microscopy. In our study, we compared the distribution of structural sterols in the plasma membrane in two types of root cells with distinct mode of elongation: diffusely expanding meristematic cells arranged in cell files and tip-growing tubular root hairs. Our results show that structural sterols were abundant at the plasma membrane of root hair apices and they were internalized into endosomal compartments. In root meristematic cells they were present in the plasma membrane and endosomal compartments, but in certain developmental zones of the root apex they were enriched in non-growing cross cell poles representing plant synapses. Both actin-enriched root hair apices and non-growing end poles of the cell surface enriched in actin and myosin VIII are cell periphery domains known to be active sites of intense endocytosis and vesicular trafficking. Enrichment of structural sterols in these domains indicates that they can be involved in the modulation of the physiological properties of the plasma membrane responsible for the maintenance of actin-dependent rapid membrane trafficking and recycling.

Supported by EU, project TIPNET (HPRN-CT-2002­00265) and by the Grant Agency VEGA (grant No. 2/5085/25)