Figure 1.

Fluorescence Localization of Sterols in Arabidopsis Root by Filipin.

(A) Fluorescence microscopy. Overview of sterol localization in the root hair formation zone. Distribution and accumulation of filipin-reactive sterols reflect the root hair formation process. Zoomed individual stages of bulge formation (A₁), growing root hair (A₂), and nongrowing root hair (A₃) shown in boxed areas.

(B) to (F₂) Nonuniform distribution of sterols in trichoblasts before and during root hair formation (B). In addition to evenly distributed filipin fluorescence in the plasma membrane, filipin-labeled sterols accumulate in small clusters in the basal pole of trichoblasts before bulge formation ([B] to [D], lateral view in [D₁]). In the early stages before bulge formation, they are randomly distributed (C). Filipin-reactive sterols are strongly enriched in the bulge ([E], lateral view in [E₁]) and in the emerging tip of the root hair ([F] to [F₂]). Globular filipin-induced structures enriched in the bulge coaccumulate FM4-64 (E₂).

(G) and (H) Accumulation of sterols in growing root hairs. Formation of apical sterol-rich clusters (arrows) after prolonged filipin treatment ([G] to [G₂]). Filipin-sterol complexes are predominantly formed in the apical and subapical zone of the growing root hair ([H], single median section in [H₁], z-projection in [H₂]).

(I) Cross section of the basal part of the apex (position marked by line in [I]) and rotation revealed that filipin-sterol complexes are closely associated with the plasma membrane ([I₁] and [I₂]).

(B) to (I) Confocal microscopy; (F) to (H) differential interference contrast (DIC) images; and (G₂) confocal-DIC merged image. Bars = 100 μm in (A), 10 μm in (B), and 5 μm in (A₁) to (A₃) and (C) to (I).