N-linked glycosylation enzymes in the diatom Thalassiosira oceanica exhibit a diel cycle in transcript abundance and favor for NXT-type sites

Joerg Behnke,Alejandro M Cohen,Julie Laroche

doi:10.1038/s41598-021-82545-1

Joerg Behnke, Alejandro M Cohen + Show 1 more

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https://doi.org/10.1038/s41598-021-82545-1

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Journal: Scientific Reports	Publication Date: Feb 5, 2021
Citations: 8	License type: open-access

Affiliation: Dalhousie University

Abstract

N-linked glycosylation is a posttranslational modification affecting protein folding and function. The N-linked glycosylation pathway in algae is poorly characterized, and further knowledge is needed to understand the cell biology of algae and the evolution of N-linked glycosylation. This study investigated the N-linked glycosylation pathway in Thalassiosira oceanica, an open ocean diatom adapted to survive at growth-limiting iron concentrations. Here we identified and annotated the genes coding for the essential enzymes involved in the N-linked glycosylation pathway of T. oceanica. Transcript levels for genes coding for calreticulin, oligosaccharyltransferase (OST), N-acetylglucosaminyltransferase (GnT1), and UDP-glucose glucosyltransferase (UGGT) under high- and low-iron growth conditions revealed diel transcription patterns with a significant decrease of calreticulin and OST transcripts under iron-limitation. Solid-phase extraction of N-linked glycosylated peptides (SPEG) revealed 118 N-linked glycosylated peptides from cells grown in high- and low-iron growth conditions. The identified peptides had 81% NXT-type motifs, with X being any amino acids except proline. The presence of N-linked glycosylation sites in the iron starvation-induced protein 1a (ISIP1a) confirmed its predicted topology, contributing to the biochemical characterization of ISIP1 proteins. Analysis of extensive oceanic gene databases showed a global distribution of calreticulin, OST, and UGGT, reinforcing the importance of glycosylation in microalgae.

Highlights

The N-linked glycosylation pathway in algae is poorly characterized, and further knowledge is needed to understand the cell biology of algae and the evolution of N-linked glycosylation
N-linked glycan structures differs based on specific enzymes in the Golgi apparatus, and while vertebrates show a high diversity of glycan structures, homologues for many of the enzymes present in vertebrates have not been identified in plants and m
As a first step in our study, we scanned the T. oceanica genome to identify the genes coding for proteins of the N-linked glycosylation pathway

Summary

Introduction

The N-linked glycosylation pathway in algae is poorly characterized, and further knowledge is needed to understand the cell biology of algae and the evolution of N-linked glycosylation. This study investigated the N-linked glycosylation pathway in Thalassiosira oceanica, an open ocean diatom adapted to survive at growth-limiting iron concentrations. We identified and annotated the genes coding for the essential enzymes involved in the N-linked glycosylation pathway of. Solid-phase extraction of N-linked glycosylated peptides (SPEG) revealed 118 N-linked glycosylated peptides from cells grown in high- and low-iron growth conditions. N-linked glycosylation is primarily used for protein folding control in the endoplasmic reticulum with additional functions based on the matured glycan structures in the Golgi apparatus. N-linked glycan structures differs based on specific enzymes in the Golgi apparatus, and while vertebrates show a high diversity of glycan structures, homologues for many of the enzymes present in vertebrates have not been identified in plants and m. The diversity of glycan structures in vertebrates is reflected in functions ranging from cell–cell communication, their involvement in auto-immune diseases, to inflammatory r eactions[5]

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