Glutamine Synthetase (GS): A Key Enzyme for Nitrogen Assimilation in The Macroalga Gracilariopsis lemaneiformis (Rhodophyta)

Abstract

This study aimed to address the importance of glutamine synthetase II (GSII) during nitrogen assimilation in macroalga Gracilariopsis lemaneiformis. The cDNA full‐length sequence of the three glGSII genes was revealed to have the 5′ m7G cap, 5′‐untranslated region, open reading frame (ORF), 3′‐untranslated region, and a 3′ poly (A) tail. The three glGSIIs were classified into plastid glGS2 and cytosolic glGS1‐1 and glGS1‐2, having conserved GSII domains but different cDNA sequences. The complicated 5′ end flanking region indicates complex function of glGS genes. glGS1 genes were significantly up‐regulated under the different NH4+: NO3− ratio (i.e., 40:10, 25:25, 10:40, and 0:50) except glGS2 which dramatically up‐regulated under the low NH4+: NO3− ratio (i.e., 10:40 and 0:50) during different cultivation times. These different expression patterns perhaps are due to the different biological roles of GS1 and GS2 in the gene family. Furthermore, hypothetical working model of nitrogen assimilation pathway exhibiting the role of glGS1 and glGS2 is proposed. Finally, glGS2 was expressed in Escherichia coli BL21 (DE3), and the optimal conditions for culture (15°C, overnight), purification (500 mM imidazole washing), and activity (pH 7.4, 37°C) were established. This study lays a very important foundation for exploring the role of GS in nitrogen assimilation in algae and plants.

MYB gene family in the diatom Phaeodactylum tricornutum revealing their potential functions in the adaption to nitrogen deficiency and diurnal cycle

“…Significant statistical differences in the relative expression of PtMYB genes under different conditions were determined by SPSS statistics (Version 19.0, SPSS Inc, IBM company, Armonk, NY, USA) with one‐way ANOVA (Liu et al. 2019). The statistical significance was considered at *P < 0.05 (Liu et al.…”

Golgi fucosyltransferase 1 reveals its role in α-1,4-fucose modification of N-glycan in Diatom Phaeodactylum tricornutum

“…However, seven DGPs related with photosynthesis, carbon and nitrogen metabolisms were found in PtFucT1-KO mutant. Especially, glutamine synthetase is a key enzyme for the assimilation of nitrogen (24). The up-or down-regulated N-glycosylation of these proteins might change the proteins' structure and subsequent function, leading to various physiological phenotypes in PtFucT1-KO mutant.…”

“…RNA isolation and cDNA synthesis were carried out according to standard procedures (24). PtFucTs sequences were fused to the upstream of eGFP and cloned into pPha-NR vector (GenBank: JN180663) via EasyGeno kit (Tiangen, Biotech Co., China).…”

Global Profiling of N-Glycoproteins and N-Glycans in the Diatom Phaeodactylum tricornutum

“…Here, taking glutamine synthase as an example, GS harbored five N-glycosylated sites in P. tricornutum . It is already known that GS was one of the most important enzymes for the nitrogen assimilation and absorption ( Liu et al, 2019 ). GS catalyzed the assimilation of ammonium into glutamate and produced glutamine in the cytoplasm, mitochondria, and chloroplast ( Konishi et al, 2016 ; Smith et al, 2019 ).…”

“…GS catalyzed the assimilation of ammonium into glutamate and produced glutamine in the cytoplasm, mitochondria, and chloroplast ( Konishi et al, 2016 ; Smith et al, 2019 ). The function of GS isoenzymes on the regulation of nitrogen metabolism was widely studied in different organisms, such as in microalgae C. reinhardtii ( Cabello et al, 2020 ) and macroalga G. lemaneiformis ( Liu et al, 2019 ). However, the N-glycosylation of GS in P. tricornutum is reported for the first time in this study.…”