Drying Increases Intracellular Partitioning of Amphiphilic Substances into the Lipid Phase

Abstract

Previously we proposed that endogenous amphiphilic substances may partition from the aqueous cytoplasm into the lipid phase during dehydration of desiccation-tolerant organ(ism)s and vice versa during rehydration. Their perturbing presence in membranes could thus explain the transient leakage from imbibing organisms. To study the mechanism of this phenomenon, amphiphilic nitroxide spin probes were introduced into the pollen of a model organism, Typha latifolia, and their partitioning behavior during dehydration and rehydration was analyzed by electron paramagnetic resonance spectroscopy. In hydrated pollen the spin probes mainly occurred in the aqueous phase; during dehydration, however, the amphiphilic spin probes partitioned into the lipid phase and had disappeared from the aqueous phase below 0.4 g water g ؊1 dry weight. During rehydration the probes reappeared in the aqueous phase above 0.4 g water g ؊1 dry weight. The partitioning back into the cytoplasm coincided with the decrease of the initially high plasma membrane permeability. A charged polar spin probe was trapped in the cytoplasm during drying. Liposome experiments showed that partitioning of an amphiphilic spin probe into the bilayer during dehydration caused transient leakage during rehydration. This was also observed with endogenous amphipaths that were extracted from pollen, implying similar partitioning behavior. In view of the fluidizing effect on membranes and the antioxidant properties of many endogenous amphipaths, we suggest that partitioning with drying may be pivotal to desiccation tolerance, despite the risk of imbibitional leakage.

Triacylglycerol phase and ‘intermediate’ seed storage physiology: a study of Cuphea carthagenensis

“…Our best speculation builds on recent ideas of partitioning of amphiphilic molecules and surface-active agents into hydrophilic or hydrophobic regions depending on water content (Golovina et al 1998;Hoekstra et al 1999). Within the triacylglycerol fraction, amphiphilic molecules may catalyze or inhibit crystallization reactions (see Walters et al 2005a), thereby explaining differences in crystallization rate, but not total crystallization, with seed water content (Figs.…”

Environmental pollution changes in membrane lipids, antioxidants and vitality of Scots pine (Pinus sylvestris L.) pollen

“…However, in these studies no explanation of the phenomenon of pollen injuries was proposed. Investigations of Hoekstra et al (1992), Wolkers and Hoekstra (1995) and Golovina et al (1998) showed that cytoplasmic membranes were prime targets for destructive changes in pollen grains as a result of abiotic stresses. There is little information in the literature about the structural and biophysical function of membranes in the tolerance of pollen grains to industrial pollution.…”

Ageing increases the sensitivity of neem (Azadirachta indica) seeds to imbibitional stress

“…This leakage is generally transient and does not lead to severe damage (Senaratna and McKersie, 1983;Hoekstra and Van der Wal, 1988). Lately, this leakage has been attributed to the transiently increased membrane permeability associated with the presence, in plasma membranes, of amphiphilic metabolites that are in the process of partitioning back into the aqueous cytoplasm during rehydration (Golovina et al, 1998). Complete loss of cell viability due to irreversible membrane damage may occur when dried anhydrobiotic cells are allowed to imbibe in relatively cold media (Hoekstra et al, 1999).…”