Cryopreservation of Doritaenopsis suspension culture by vitrification

Cryopreservation of plant cell cultures - Diverse practices and protocols

Plant cell cultures can be used as biotechnological platforms for the commercial production of small-molecule active ingredients and recombinant proteins, such as biopharmaceuticals. This requires the cryopreservation of well-characterized cell lines as master cell banks from which uniform working cell banks can be derived to ensure high batch-to-batch reproducibility during production campaigns. However, the cryopreservation of plant cells is challenging due to their low viability and poor regrowth after thawing. Three approaches have been developed: slow freezing, vitrification, and encapsulation-dehydration. Typically, the protocols are iteratively adapted to accommodate the properties of different plant cell lines, taking time and resources while achieving moderate success. Since standardized processes are a prerequisite for industrial applications, this review presents an in-depth analysis of the different procedures for cryopreservation of plant suspension cell cultures, highlighting relevant parameters for effective cryopreservation and the re-establishment of vigorous plant cell cultures within weeks. The protocol variants are grouped into modules that facilitate the directed improvement of each step and allow protocol evolution by module recombination. Ultimately, such improved cryopreservation protocols will form the basis of processes that comply with good manufacturing practice and attract major biopharmaceutical companies to the benefits of plant molecular farming.

In vitro propagation and cryopreservation of Aerides odorata Lour. (Orchidaceae)

An efficient method for in vitro propagation and cryopreservation of Aerides odorata was established. Leaf segments were cultured on New Dogashima (ND) mediums supplemented with various concentrations of Benzyladenine (BA) (0-5 mg L(-1)) combined with Naphthaleneacetic Acid (NAA) (0-2 mg L(-1)). The optimal treatment for inducing Protocorm-like Bodies (PLBs) from leaf segments was obtained from the combination of 1 or 3 mg L(-1) BA and 0.5 or 1 mg L(-1) NAA; whereas, the addition of BA or NAA alone induced shoot and/or root initiation rather than PLB or callus formation. Shoots rapidly developed on ND mediums containing 5 mg L(-1) BA. Cryopreservation of leaf segment-derived PLBs was successful using the encapsulation-dehydration method. The maximum survival percentage of Cryopreserved (Cryp) PLBs was achieved by encapsulating PLBs with 2% Na-alginate combined with 2 M glycerol and 0.4 M sucrose. The encapsulated PLBs were then precultured in 0.75 M sucrose for 24 h and dehydrated for 6 h before plunging into liquid nitrogen. Genetic stability of Cryp PLBs after regrowth was assessed by flow cytometry. The findings showed no different patterns of ploidy levels and morphology between Cryp and non-cryopreserved (Ncryp) control plantlets.

Cryopreservation of immature seeds of Bletilla striata by vitrification

An efficient protocol was established for the cryopreservation of immature seeds of a terrestrial orchid, Bletilla striata. Immature seeds collected 2-4 months after pollination (MAP) were treated using three different cryogenic procedures: (1) direct plunging into liquid nitrogen, (2) vitrification, and (3) vitrification with preculture. When immature seeds collected 3 MAP and 4 MAP were precultured for 3 days on New Dogashima medium supplemented with 0.3 M sucrose and cryopreserved by vitrification, the survival rate after preservation, as assessed by staining with 2,3,5-triphenyltetrazolium chloride, was 92% and 81%, respectively. Immature seeds thus treated showed no decrease in germination rate relative to untreated immature seeds, and they developed into normal plantlets in vitro.