Membrane fractionation and enrichment of callose synthase from pollen tubes of Nicotiana alata Link et Otto

Abstract

The callose synthase (UDP-glucose: 1,3-beta-D-glucan 3-beta-D-glucosyl transferase; EC 2.4.1.34) enzyme (CalS) from pollen tubes of Nicotiana alata Link et Otto is responsible for developmentally regulated deposition of the cell wall polysaccharide callose. Membrane preparations from N. alata pollen tubes grown in liquid culture were fractionated by density-gradient centrifugation. The CalS activity sedimented to the denser regions of the gradient, approximately 1.18 g.ml-1, away from markers for Golgi, endoplasmic reticulum and mitochondria, and into fractions enriched in ATPase activity and in membranes staining with phosphotungstic acid at low pH. This suggests that pollen-tube CalS is lo..