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Updated: Nov 22, 2025

Measuring the Osmotic Water Permeability Coefficient Pf of Spherical Cells: Isolated Plant Protoplasts as an Example
Published on: October 8, 2014
Plasma membrane vesicles from cauliflower meristematic tissue and their role in water passage
Paula Garcia-Ibañez1, Juan Nicolas-Espinosa1, Micaela Carvajal2
1Aquaporins Group, Centro de Edafología y Biología Aplicada del Segura, CEBAS-CSIC, Campus Universitario de Espinardo-25, E-30100, Murcia, Spain.
Background:
Cauliflower (Brassica oleracea L. var. botrytis) inflorescences are composed mainly of meristematic tissue, which has a high cellular proliferation. This considerable cellular density makes the inflorescence an organ with a large proportion of membranes. However, little is known about the specific role of the lipid and protein composition of the plasma membrane present in this organ.
Results:
In this work, we analyzed the lipids and proteins present in plasma membrane from two different stages of development of cauliflower inflorescence and compared them with leaf plasma membrane. For this purpose, plasma membrane vesicles were obtained by centrifugation for each sample and the vesicular diameter and osmotic permeability (Pf) were analyzed by dynamic light scattering and the stopped-flow technique, respectively. In addition, fatty acids and sterols were analyzed by gas chromatography and HPLC. The protein composition of the inflorescences and leaves was characterized by HPLC-ESI-QTOF-MS and the data obtained were compared with Brassicaceae proteins present in the UniProt database in relation to the presence of aquaporins determined by western blot analysis. The highest Pf value was found in 90 day inflorescences-derived plasma membrane vesicles (61.4 ± 4.14 μms- 1). For sterols and fatty acids, the concentrations varied according to the organ of origin. The protein profile revealed the presence of aquaporins from the PIP1 and PIP2 subfamilies in both inflorescences and leaves.
Conclusion:
This study shows that the composition of the sterols, the degree of unsaturation of the fatty acids, and the proteins present in the membranes analyzed give them high functionality for water passage. This represents an important addition to the limited information available in this field.
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