Massive cellular disruption occurs during early imbibition of Cuphea seeds containing crystallized triacylglycerols

Abstract

The transition from anhydrobiotic to hydrated state occurs during early imbibition of seeds and is lethal if lipid reserves in seeds are crystalline. Low temperatures crystallize lipids during seed storage. We examine the nature of cellular damage observed in seeds of Cuphea wrightii and C. lanceolata that differ in triacylglycerol composition and phase behavior. Intracellular structure, observed using transmission electron microscopy, is profoundly and irreversibly perturbed if seeds with crystalline triacylglycerols are imbibed briefly. A brief heat treatment that melts triacylglycerols before imbibition prevents the loss of cell integrity; however, residual effects of cold treatments in C. wrightii cells are reflected by the apparent coalescence of protein and oil bodies. The timing and temperature dependence of cellular changes suggest that damage arises via a physical mechanism, perhaps as a result of shifts in hydrophobic and hydrophilic interactions when triacylglycerols undergo phase changes. Stabilizers of oil body structure such as oleosins that rely on a balance of physical forces may become ineffective when triacylglycerols crystallize. Recent observations linking poor oil body stability and poor seed storage behavior are potentially explained by the phase behavior of the storage lipids. These findings directly impact the feasibility of preserving genetic resources from some tropical and subtropical species.

Effects of temperature and desiccation on ex situ conservation of nongreen fern spores

“…1A ). Regression analysis of time dependency that freezer storage may actually accelerate deterioration of nongreen fern spores, and this syndrome of damage is symptomatic of seeds that have been categorized with intermediate-type physiology ( Crane et al, 2003Volk et al, 2006 ).…”

Elevation of oil body integrity and emulsion stability by polyoleosins, multiple oleosin units joined in tandem head-to-tail fusions

“…Neither of the freezing treatments to dry seeds, −20 °C (this manuscript) or −30 °C (Shimada et al. , 2008), appears to have resulted in cellular disruption caused by crystallized triacylglycerols which have been linked with reduced germination in freeze‐treated (−18 or −80 °C) Cuphea wrightii seeds (Volk et al. , 2006).…”

“…, 2006). In this case, damage from crystallized triacylglycerols was prevented if the frozen seeds were kept dry and heated to 42 °C prior to imbibition (Volk et al. , 2006).…”

Pretreatment incubation for culture and cryopreservation of Sabal embryos

“…Seeds of Sabal species, such as S. maritima and S. palmetto, contain a high quantity of medium-chain fatty acids, including lauric acid (C 12 ) and myristic acid (C 14 ) (Rodríguez-Leyes et al 2007). These medium-chain fatty acids have a high melting temperature and seeds containing a high concentration of such fatty acids are sensitive to low temperatures (Crane et al 2003Volk et al 2006). It can also be presumed that medium-chain fatty acids are crystallized during low-temperature storage prior to embryo isolation, and the transition from the anhydrobiotic to hydrated state, i.e.…”