Review: The case for studying mitochondrial function during plant cryopreservation

Critical Role of Regrowth Conditions in Post-Cryopreservation of In Vitro Plant Germplasm

“…These injuries include potential mechanical damage by extracellular ice (in the programmed/slow freezing method), osmotic stress due to severe dehydration and application of highly concentrated CPA mixtures, increasing cytoplasm viscosity, and accumulating toxic solutes. These factors, acting collectively with cytotoxicity of high doses of CPA, result in extensive damage to cryopreserved tissues that have been reviewed in detail [ 33 , 39 , 40 ]. The ultrastructural studies of plant material at various stages of cryopreservation revealed significant changes in the intracellular integrity or organization of cells, damage to membrane structures, including plasmalemma, cell lysis, fragmentation of intracellular compartments, etc.…”

“…The ultrastructural studies of plant material at various stages of cryopreservation revealed significant changes in the intracellular integrity or organization of cells, damage to membrane structures, including plasmalemma, cell lysis, fragmentation of intracellular compartments, etc. [ 40 , 41 , 42 ]. Extensive stress leads to the boost of the reactive oxygen species (ROS) and the rapid development of oxidative stress (discussed below).…”

“…Carbon and energy metabolism-related proteins were the most substantially altered after cryopreservation of the protocorm-like bodies of Dendrobium nobile orchid [ 47 ]. Whelehan et al [ 40 ] concluded that cryopreservation-induced cell damages significantly negatively impact energy metabolism, particularly reducing mitochondria functionality. The adenosine triphosphate (ATP) concentration in potato shoot tips changed on average from 28.9 nmol g −1 fresh weight (FW) to 5.6 nmol g −1 FW as a result of the cryopreservation procedure [ 48 ].…”

“…The expansive nature of cryopreservation-induced injuries suggest that, at the recovery stage, cells should be provided with a supportive environment to rapidly repair the reversible damages to cellular components, restore normal cell functioning, and regain the capability to proliferate and produce new tissues. This process is energy intensive [ 40 ] and is often “the race against time”, given the rapidly accumulating ROS and toxic chemicals in the injured specimens. Therefore, the conditions at the recovery stage should serve the following purposes: Provide optimum conditions for recovery without posing extra stress to already damaged plant materials; Remove toxic chemicals (residues of CPA, toxic substances released from the damaged cells, phenolic compounds, etc.…”

“…The positive action of melatonin during cryopreservation is likely due to its activity as a direct ROS scavenger and as a phytohormone playing a vital role in the signaling networks and metabolic regulation [ 168 ]. Whelehan et al [ 40 ] also pointed out that some metabolites formed when melatonin reacts with ROS are highly effective free radical scavengers [ 169 , 170 ]. For example, cyclic-3-hydroxymelatonin has been reported to prevent ROS damage, specifically to cytochrome c, and induce the cascade of effects for preventing programmed cell death [ 40 , 170 ].…”