Abstract

Algal biofuels are considered to be a major potential source of renewable energy in the future, specifically for biodiesel production. Of the various types of molecules that can be used as biofuels, biodiesel stands out as the best candidate for mass production, taking into account our current internal combustion engine technology and energy distribution infrastructure. Biodiesel can be synthesized via the transesterification of triacylglycerols (TAGs), and although there has been much research into the environment and growth factors that control the production of TAGs in algae, little is known about the genes and proteins that make up the biosynthesis pathway in different algal species.My project is to identify and characterize the genes that catalyse the final step in TAG biosynthesis in several different algal species, with my primary focus being on Phaeodactylum tricornutum, a marine diatom that has been identified as a very good candidate for mass production of algal biodiesel. One of the enzymes that catalyses the final step in TAG biosynthesis in all eukaryotes is known as diacylglycerol acyltransferase type-2 (DGAT2). While the vast majority of higher plants, animals and yeast possess only one copy of the DGAT2 gene, I have found that the majority of algal species encode between two and five putative DGA T2s. These putative DGA T2s are not the result of recent gene duplications since amino acid similarity algorithms indicate that the algal DGA T2s within the same species are less related to each other than they are to higher plant or opisthokont DGA T2s,which form two clear and distinct phylogeny clades. I have cloned the five DGAT2 isoforms from P. tricornutum and have successfully shown that at least one isoform can rescue the TAG -less phenotype of a yeast mutant that is completely deficient in TAG production when expressed under the control of the GAL promoter.