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

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

doi:10.3389/fbioe.2023.1259587

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

Front Bioeng Biotechnol. 2023 Sep 18:11:1259587. doi: 10.3389/fbioe.2023.1259587. eCollection 2023.

Authors

Affiliations

¹ School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan.
² National Institute of Technology, Tsuruoka College, Tsuruoka, Japan.
³ University of Lille, French National Centre for Scientific Research, UMR8576-UGSF-Unité de Glycobiologie Structurale et Fonctionnelle, Lille, France.

^# Contributed equally.

Abstract

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

Keywords: Haptophyta; coccolithophorid; glucan synthase; storage glucan; transglycosylase; β-glucan.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This study received funding from JSPS KAKENHI Grant Number 20K06326, and the Promotion and Mutual Aid Corporation for Private Schools. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article, or the decision to submit it for.