AUTHOR=Inukai Mayuka , Kobayashi Naoya , Endo Hirotoshi , Asakawa Koki , Amano Keisuke , Yasuda Yuki , Cenci Ugo , Colleoni Christophe , Ball Steven , Fujiwara Shoko 

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

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=11

YEAR=2023

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2023.1259587

DOI=10.3389/fbioe.2023.1259587

ISSN=2296-4185

ABSTRACT=<p>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 <italic>Pleurochrysis haptonemofera</italic>. RNAi of <italic>PhTGS</italic> 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. <italic>PhTGS</italic> was expressed more in light, where β-glucan was actively produced by photosynthesis, than in the dark. The crude extract of <italic>E</italic>. <italic>coli</italic> expressing PhKre6 demonstrated its activity to incorporate <sup>14</sup>C-UDP-glucose into β-glucan of <italic>P. haptonemofera</italic>. These findings suggest that PhTGS functions in storage β-glucan synthesis specifically in light, probably by producing the β-1,6-branch.</p>