Electron microscopic autoradiography of β-glucans synthesized by a membrane fraction from pollen tubes of Petunia hybrida

Alkaline extraction of a membrane fraction from Petunia pollen tubes left an alkali-insoluble fraction that consisted of microfibrils embedded in amorphous material. The amorphous material was partially separated from the microfibrils by disaggregation with ultrasound or by solubilization with hydrogen peroxide/glacial acetic acid. Previously it was shown that incubation of the membrane fraction with UDP-[U-14C]glucose gave an alkali-insoluble fraction containing labelled fi-glucans. EM-autoradiography of this fraction, after labelling with UDP-[6-3H]glucose, showed that in vitro synthesized (3-glucans did not self-assemble but bound strongly to pre-existing microfibrils. Applicability of EM-autoradiography for confirmation of in vitro synthesis of microfibrils is discussed.