Identification and characterization of glutamine synthetase isozymes in Gracilaria lemaneiformis

Algal metabolites are the most promising feedstocks for bio‐energy production. Gracilariopsis lemaneiformis seems to be a good candidate red alga for polysaccharide production, especially relating to the agar production industry. Nitrogen deficiency is an efficient environmental pressure used to increase the accumulation of metabolites in algae. However, there are no studies on the physiological effects of G. lemaneiformis in response to nitrogen deficiency and its subsequent recovery. Here we integrated physiological data with molecular studies to explore the response strategy of G. lemaneiformis under nitrogen deficiency and recovery. Physiological measurements indicated that amino acids and protein biosynthesis were decreased, while endogenous NH4+ and soluble polysaccharides levels were increased under nitrogen stress. The expression of key genes involved in these pathways further suggested that G. lemaneiformis responded to nitrogen stress through up‐regulation or down‐regulation of genes related to nitrogen metabolism, and increased levels of endogenous NH4+ to complement the deficiency of exogenous nitrogen. Consistent with the highest accumulation of soluble polysaccharides, the gene encoding UDP‐glucose pyrophosphorylase, a molecular marker used to evaluate agar content, was dramatically up‐regulated more than 4‐fold compared to the relative expression of actin after 4 d of nitrogen recovery. The present data provide important information on the mechanisms of nutrient balance in macroalgae.

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“…, Liu et al. ). Therefore, GS plays an important role in N assimilation from inorganic N to organic N (Liu et al.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, GS plays an important role in N assimilation from inorganic N to organic N (Liu et al. ). The relative expression of gs gene was significantly increased at 8 h and 10 d of N deficiency in Gracilariopsis lemaneiformis .…”

Section: Discussionmentioning

confidence: 99%

Physiological effects of nitrogen deficiency and recovery on the macroalga Gracilariopsis lemaneiformis (Rhodophyta)

Liu

Wen

Chen

et al. 2019

Journal of Phycology

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“…However, this inorganic nitrogen must be processed and assimilated into organic nitrogen glutamine for the synthesis of N‐containing compounds, including proteins, hormones, and vitamins (Liu et al. ). Nitrogen deficiency has been proven to affect physiological function and gene expression, which results in low yield and poor quality of plants and microalgae (Robertson and Vitousek , Wang et al.…”

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confidence: 99%

“…2018b); therefore, it is widely cultivated along the coasts of China (Liu et al. ). Our previous study revealed that the shortage of inorganic nitrogen had severely limited the growth and productivity of G. lemaneiformis and resulted in disease outbreak (Wang et al.…”

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confidence: 99%

“…We previously identified six GS genes from the transcriptome data of G. lemaneiformis (Liu et al. ), and further analysis revealed that two genes encode GSI isoforms, three genes encode GSII isoforms, and one gene encodes GSIII isoform. GSII family contains one gene ( glGS2 ) encoding putative plastid GS2 and two genes ( glGS1‐1 and glGS1‐2 ) encoding putative cytosolic GS1.…”

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confidence: 99%

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

Liu

Huan

Zhang

et al. 2019

Journal of Phycology

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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.

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The impact of nitrogen deficiency and subsequent recovery on the photosynthetic performance of the red macroalga Gracilariopsis lemaneiformis

et al. 2019

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Identification and characterization of glutamine synthetase isozymes in Gracilaria lemaneiformis

Cited by 13 publications

References 33 publications

Physiological effects of nitrogen deficiency and recovery on the macroalga Gracilariopsis lemaneiformis (Rhodophyta)

Physiological effects of nitrogen deficiency and recovery on the macroalga Gracilariopsis lemaneiformis (Rhodophyta)

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

The impact of nitrogen deficiency and subsequent recovery on the photosynthetic performance of the red macroalga Gracilariopsis lemaneiformis

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