Furtula V, Khan I A, Nothnagel E A
Department of Botany and Plant Sciences, University of California, Riverside 92521.
Proc Natl Acad Sci U S A. 1990 Sep;87(17):6532-6. doi: 10.1073/pnas.87.17.6532.
Osmotic levels in the range typically used during plant protoplast isolation and incubation were investigated with regard to effects on the lateral diffusion of lipid probes in the plasma membrane. The lateral diffusion coefficient of a fluorescent sterol probe in the plasma membrane of maize (Zea mays L.) root protoplasts in a medium containing 0.45 M mannitol was 4 times faster than when the medium contained 0.9 M mannitol. The lateral diffusion coefficient of a fluorescent phospholipid probe, however, did not change over this range of mannitol concentrations. Similar diffusion characteristics were observed when the medium contained trehalose instead of mannitol. Slower lateral diffusion of the sterol probe at higher osmolality was also observed when KCl/CaCl2-based osmotic media were used with protoplasts isolated by a mechanical, rather than by an enzymic, method. Extraction and quantitation of total lipids from protoplasts showed that both the phospholipid and sterol contents per protoplast decreased with increasing osmolality, while the sterol/phospholipid ratio increased. These results demonstrate that osmotic stress induces selective changes in both the composition and biophysical properties of plant membranes.
研究了植物原生质体分离和培养过程中常用的渗透压水平对质膜中脂质探针侧向扩散的影响。在含有0.45M甘露醇的培养基中，玉米（Zea mays L.）根原生质体质膜中荧光甾醇探针的侧向扩散系数比培养基含有0.9M甘露醇时快4倍。然而，荧光磷脂探针的侧向扩散系数在该甘露醇浓度范围内没有变化。当培养基含有海藻糖而不是甘露醇时，也观察到了类似的扩散特性。当使用基于KCl/CaCl2的渗透介质与通过机械而非酶法分离的原生质体时，在较高渗透压下也观察到甾醇探针的侧向扩散较慢。从原生质体中提取和定量总脂质表明，每个原生质体的磷脂和甾醇含量均随渗透压的增加而降低，而甾醇/磷脂比值增加。这些结果表明，渗透胁迫会诱导植物膜的组成和生物物理性质发生选择性变化。
