Current issues in plant cryopreservation and importance for ex situ conservation of threatened Australian native species

Abstract

An alarming proportion of Australia’s unique plant biodiversity is under siege from a variety of environmental threats. Options for in situ conservation are becoming increasingly compromised as encroaching land use, climate change and introduced diseases are highly likely to erode sanctuaries regardless of best intentions. Ex situ conservation is currently limited to botanic garden living collections and seed banking, with in vitro and cryopreservation technologies still being developed to address ex situ conservation of species not amenable to conventional storage. Cryopreservation (storage in liquid nitrogen) has been used successfully for long-term biosecure storage of shoot tips of several species of threatened Australian plants. We present a case for building on this research and fostering further development and utilisation of cryopreservation as the best means of capturing critical germplasm collections of Australian species with special storage requirements (e.g. recalcitrant-seeded taxa and species with short-lived seeds) that currently cannot be preserved effectively by other means. This review highlights the major issues in cryopreservation that can limit survival including ice crystal damage and desiccation, toxicity of cryoprotective agents, membrane damage, oxidative stress and mitochondrial function. Progress in understanding and mitigating these stresses is vital for advancing cryopreservation for conservation purposes.

Application of the MSAP Technique to Evaluate Epigenetic Changes in Plant Conservation

“…ROS interact with cellular biomolecules, and can cause serious oxidative damage to proteins, nucleic acids and lipids [ 53 , 54 ]. Furthermore, some of the by-products of lipid peroxidation, such as the aldehydes malondialdehyde (MDA) and 4-hydroxy-2-nonenal (4-HNE), are highly reactive [ 55 ]. Both molecules have been shown to interact with proteins (leading to loss of function) and DNA (leading to mutations) or inhibit DNA and protein synthesis [ 53 , 56 ].…”

“…Cryopreservation is the storage of live cells, tissues or organs at temperatures below −150 °C, which ensures an extremely low metabolism, allowing long-term storage. As mentioned before, these techniques have special importance when conserving diversity of plants with recalcitrant seeds, short-lived seeds or vegetatively propagated [ 55 , 90 , 91 , 92 ]. Worldwide there are over 700,000 cryopreserved accessions of crop species representing 13.12% of the total number preserved in germplasm banks [ 49 ].…”

“…The treatments imposed on cells to avoid intracellular ice formation or extreme dehydration produce stresses at the cellular level that, although they may not lead to cellular death, could produce alterations in biomolecules [ 55 ]. Damages to cells have been related to the toxicity of cryoprotectants, cell membrane integrity alteration, mitochondria disruption, or oxidative stress [ 55 , 95 ]. Oxidative stress constitutes a major component of cryo-injury, caused primarily by ROS [ 95 , 96 ].…”

Applications of Biotechnology for Characterization of Plants and Pests as the Key Components of Plant Protection and Production Strategies: A Review

“…Endemic plant species are usually more vulnerable to anthropogenic threats and natural changes and, therefore, hold a higher extinction risk. To this effect, various conservation strategies need to be practiced such as ex-situ conservation exercised in botanic gardens (Mounce et al, 2017), in-situ conservation (Heywood, 2015;Whitlock et al, 2016), cryopreservation (Kaviani, 2011;Streczynski et al, 2019;Coelho et al, 2020) and biotechnological methods such as in-vitro preservation in TC collection including short-, medium-, and long-term strategies (Rao, 2004;Rajasekharan and Sahijram, 2015;Yohannes and Woldesemaya, 2017;Salgotra et al, 2019;Coelho et al, 2020). The DNA bank is an efficient, simple and long-term method used in conserving genetic resource for biodiversity.…”

Cryopreservation for Tree Species with Recalcitrant Seeds: the Avocado Case

“…Theoretically, cryopreserved materials can be stored indefinitely without any genotypic and phenotypic variations [16], offering an attractive approach to conserve germplasm of both shoot tips and somatic embryos [17]. Cryopreservation is currently the only available alternative for long-term storage of recalcitrant-seeded species such as avocado [12,20].…”