Thermotropic Properties of Lipids Extracted from Plasma Membrane and Tonoplast Isolated from Chilling-Sensitive Mung Bean (Vigna radiataL. Wilczek)1

摘要

Measurements by differential scanning calorimetry (DSC) were carried out to investigate the thermotropic properties of lipids extracted from plasma membrane and tonoplast which were isolated from the chilling-sensitive mung bean (Vigna radiataL. Wilczek). Hydrated micelles of the total lipid fractions extracted from plasma membrane and tonoplast showed phase transitions at 3°C and 9°C, respectively. DSC measurements on the separated classes of lipids revealed that glucocerebroside, a major glycolipid in these membranes, and a highly saturated phospholipid are involved in the phase transitions of the total lipid fractions. Glucocerebrosides extracted from plasma membrane and tonoplast showed phase transitions with onset temperatures at 38°C and 35°C, respectively. The total phospholipid fractions from plasma membrane and tonoplast also showed phase transitions at 9°C and 11°C, respectively. However, the addition of glucocerebroside to the total phospholipid fraction in a proportion close to that found in natural membranes resulted in increases in the phase transition temperatures of 4 to 5°C, suggesting a dominant role of the glycolipid in determining the phase behaviors of the total lipid fractions. From these data, it is suggested that a low-temperature-induced phase transition or phase separation of a highmelting- point glucocerebroside and/or a highly saturated phospholipid in plasma membranes and tonoplasts may participate in the mechanisms involved in chilling injury in