Molecular characterization of nitrate uptake and assimilatory pathway in Arthrospira platensis reveals nitrate induction and differential regulation

Abstract

The nitrate assimilation pathway and its regulation in the high-protein neutraceutical cyanobacterium, Arthrospira (Spirulina), were studied. A complete characterization of the genes of the nitrate uptake and assimilatory pathway in Arthrospira platensis strain PCC 7345 was done including cloning, sequencing, phylogenetic analysis and expression studies. Genomic localization studies revealed that their clustering is different from the operons known in other cyanobacteria; only nrtP and narB are organized together, while nirA, glnA and gltS exist in separate genomic locations. The presence of both types of nitrate transporters (nrtP/ABC types) in A. platensis is rare, as their occurrence is usually specific to marine and freshwater microorganisms, respectively. The positive effect of nitrate on transcript accumulation of narB, nirA and nrtP genes in N-depleted and N-restored cultures confirmed nitrate induction, which is abolished by the addition of ammonium ions into the medium. Gene expression studies in response to nitrate, nitrite, ammonium and glutamine provided the first evidence of differential regulation of multiple genes of nitrate assimilatory pathway in Arthrospira.

Integrative Transcriptomic and Proteomic Analysis Reveals an Alternative Molecular Network of Glutamine Synthetase 2 Corresponding to Nitrogen Deficiency in Rice (Oryza sativa L.)

“…Honglian-type cytoplasmic sterility (CMS) is one of the three major CMS for three-line hybrid rice generation, and the hybrid rice variety LY9348 produced by Honglian-type male sterile line Longhong4A demonstrates remarkable agricultural characteristics, such as high yield, broad adaptability, disease resistance, insect resistance, high temperature tolerance, and high nitrogen use efficiency (NUE) [5,6]. Nitrogen (N), one of the essential nutrient elements for plant growth and yield [7,8], is not only a key component for building up many cell functional molecules, such as nucleic acid, ATP, amino acid, chlorophyll, and various plant hormones, but also a key regulator of many biological processes, including amino acid metabolism, carbon metabolism, and protein synthesis [9]. Furthermore, if used as the main fertilizer factor to increase rice yield, N fertilizer plays an essential role in guaranteeing the high and stable rice production in China annually.…”

“…Nitrogen (N), one of the essential nutrient elements for plant growth and yield [ 7 , 8 ], is not only a key component for building up many cell functional molecules, such as nucleic acid, ATP, amino acid, chlorophyll, and various plant hormones, but also a key regulator of many biological processes, including amino acid metabolism, carbon metabolism, and protein synthesis [ 9 ]. Furthermore, if used as the main fertilizer factor to increase rice yield, N fertilizer plays an essential role in guaranteeing the high and stable rice production in China annually.…”