Suppression of DYRK ortholog expression affects wax ester fermentation in Euglena gracilis

In the microalga Euglena gracilis, the storage polysaccharide paramylon (β-1,3-D-glucan) is degraded to glucose, and finally converted to wax esters under anaerobic conditions. The wax esters and paramylon are now considered to be valuable materials for applications in biofuel production and in medicine. Genetic improvements of wax esters and paramylon accumulation in Euglena would facilitate their large-scale industrial applications; however, such improvements have thus far been difficult to realize because the regulatory factors involved in the wax ester fermentation pathway remain mostly unknown. Recently, two of dual-specificity Tyr phosphorylation-regulated kinases, starch degradation 1 (STD1) and triacylglycerol accumulation regulator 1 (TAR1), have been reported to regulate triacylglycerol metabolism in Chlamydomonas reinhardtii. In this study, we identified the Euglena DYRK orthologous sequences, and gene-silencing of EgSTD1 and EgSTD2 showed an increase in accumulation of paramylon and the following anaerobic wax ester production. This result indicated that EgSTD1 and EgSTD2 play a significant role in regulation of the wax ester fermentation pathway.