Kre6 (yeast 1,6-β-transglycosylase) homolog, PhTGS, is essential for β-glucan synthesis in the haptophyte .

Haptophytes synthesize unique β-glucans containing more β-1,6-linkages than β-1,3 linkages, as a storage polysaccharide. To understand the mechanism of the synthesis, we investigated the roles of Kre6 (yeast 1,6-β-transglycosylase) homologs, PhTGS, in the haptophyte . RNAi of repressed β-glucan accumulation and simultaneously induced lipid production, suggesting that PhTGS is involved in β-glucan synthesis and that the knockdown leads to the alteration of the carbon metabolic flow. was expressed more in light, where β-glucan was actively produced by photosynthesis, than in the dark. The crude extract of . expressing PhKre6 demonstrated its activity to incorporate C-UDP-glucose into β-glucan of . These findings suggest that PhTGS functions in storage β-glucan synthesis specifically in light, probably by producing the β-1,6-branch.