The first evidence for genotypic stability in a cryopreserved transgenic diatom

Future algal biotechnology will need enhanced
production strains, capable of more rapid growth, more
efficient solar-energy conversion and/or higher levels of
metabolite production. Almost certainly transgenic organisms
will be used to ensure the cost-effective, economically
viable production of a range of metabolites. As with all
biotechnological processes, the functional stability, reliability
and security of the production strains will be of paramount
importance in algal biotechnology, as without this no
biotechnological process is sustainable. In this study, the
transgenic model strain Thalassiosira pseudonana CCAP
1085/23 was cryopreserved using a conventional, lowtech,
colligative cryopreservation protocol. This employed
dimethyl sulphoxide [5 % (v/v)] as a cryoprotectant, using a
two-step cooling approach: initial controlled-rate cooling,
followed by plunging into liquid nitrogen. High levels of
post-thaw viability (70¿85 %) were obtained, and on recovery
of cryopreserved material no reduction in expression of
the protein of the inserted gene (big1-GFP) was observed.
Additionally, cryopreservation does not affect the
localisation of the BIG1-GFP protein as demonstrated by
microscopy of stained samples, nor its functionality as demonstrated
by Western blotting.