Expression of novel nitrate reductase genes in the harmful alga, Chattonella subsalsa

Abstract

Eukaryotic nitrate reductase (NR) catalyzes the first step in nitrate assimilation and is regulated transcriptionally in response to external cues and intracellular metabolic status. NRs are also regulated post-translationally in plants by phosphorylation and binding of 14-3-3 proteins at conserved serine residues. 14-3-3 binding motifs have not previously been identified in algal NRs. A novel NR (NR2-2/2HbN) with a 2/2 hemoglobin domain was recently described in the alga Chattonella subsalsa. Here, a second NR (NR3) in C. subsalsa is described with a 14-3-3 binding motif but lacking the Heme-Fe domain found in other NRs. Transcriptional regulation of both NRs was examined in C. subsalsa, revealing differential gene expression over a diel light cycle, but not under constant light. NR2 transcripts increased with a decrease in temperature, while NR3 remained unchanged. NR2 and NR3 transcript levels were not inhibited by growth on ammonium, suggesting constitutive expression of these genes. Results indicate that Chattonella responds to environmental conditions and intracellular metabolic status by differentially regulating NR transcription, with potential for post-translational regulation of NR3. A survey of algal NRs also revealed the presence of 14-3-3 binding motifs in other algal species, indicating the need for future research on regulation of algal NRs.

Effect of nitrogen supply on nitrogen metabolism in the citrus cultivar ‘Huangguogan’

“…The expression of the HgNR gene increased significantly with increasing N rates. Similarly, N significantly enhanced the transcription levels of HgNiR , HgGS , HgGDH , and HgAS genes, indicating that the genes are regulated in response to N fertilizer rate [ 55 – 57 ]. Previous studies have shown that the expression of nitrate assimilation genes is controlled by nitrate content in plants.…”

Recent Progress in the Study of Peroxiredoxin in the Harmful Algal Bloom Species Chattonella marina

“…During diurnal vertical migration, various biological characteristics of Chattonella species, especially those related to photosynthesis, have also been reported to display clear diurnal changes. Those characteristics include phosphate metabolism [ 91 ], nitrate reductase gene expression [ 92 ], cell division [ 93 ], and production of reactive oxygen species (ROS) [ 94 ]. The regulation of the diurnal variation of these biological characteristics of Chattonella species is complex.…”

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

“…, Wang et al. 2018a). It was known that GSII consists of cytosolic GS1 and chloroplastic GS2 isoenzymes (Diaz et al.…”

“…The GS family contains GSI, GSII, and GSIII groups based on the molecular size and the number of subunits (Ghoshroy et al 2010). The number, expression, and function of GSII isoenzymes were most widely studied in higher plants and microalgae (Glibert et al 2016, Moison et al 2018, N emeth et al 2018, Wang et al 2018a. It was known that GSII consists of cytosolic GS1 and chloroplastic GS2 isoenzymes (Diaz et al 2008).…”