The Signal Transduction Protein PII Controls Ammonium, Nitrate and Urea Uptake in Cyanobacteria

Abstract

P II signal transduction proteins are widely spread among all domains of life where they regulate a multitude of carbon and nitrogen metabolism related processes. Non-diazotrophic cyanobacteria can utilize a high variety of organic and inorganic nitrogen sources. In recent years, several physiological studies indicated an involvement of the cyanobacterial P II protein in regulation of ammonium, nitrate/nitrite, and cyanate uptake. However, direct interaction of P II has not been demonstrated so far. In this study, we used biochemical, molecular genetic and physiological approaches to demonstrate that P II regulates all relevant nitrogen uptake systems in Synechocystis sp. strain PCC 6803: P II controls ammonium uptake by interacting with the Amt1 ammonium permease, probably similar to the known regulation of E. coli ammonium permease AmtB by the P II homolog GlnK. We could further clarify that P II mediates the ammonium- and dark-induced inhibition of nitrate uptake by interacting with the NrtC and NrtD subunits of the nitrate/nitrite transporter NrtABCD. We further identified the ABC-type urea transporter UrtABCDE as novel P II target. P II interacts with the UrtE subunit without involving the standard interaction surface of P II interactions. The deregulation of urea uptake in a P II deletion mutant causes ammonium excretion when urea is provided as nitrogen source. Furthermore, the urea hydrolyzing urease enzyme complex appears to be coupled to urea uptake. Overall, this study underlines the great importance of the P II signal transduction protein in the regulation of nitrogen utilization in cyanobacteria.

From cyanobacteria to Archaeplastida: new evolutionary insights into PII signalling in the plant kingdom

“…A feature distinguishing the E. coli and Synechococcus proteins is their mode of covalent modification under N-limiting conditions: whereas PII from E. coli and other proteobacteria is uridylylated by a Gln-regulated uridylyl-transferase at a tyrosine residue (Y51) located on the large surfaceexposed T-loop, the cyanobacterial PII protein is phosphorylated at a neighbouring seryl residue (S49) by an as yet uncharacterized protein serine kinase activity (Sp€ at et al, 2015). Modification of the T-loop, together with the binding of effector molecules, determines the interaction of PII with various targets (enzymes, transport channels, transcription factors and other target proteins) (Huergo et al, 2013;Watzer et al, 2019).…”

“…Early work showed that the expression of AtGLB1, the gene encoding PII in Arabidopsis, is controlled by light but also by N and C metabolites, as the AtGLB1 mRNA levels are repressed by amino acids and induced by sucrose (Hsieh et al, 1998). Nitrite uptake and sensitivity were shown to be higher in Arabidopsis PII knockout mutants than in the wild-type (Ferrario-M ery et al, 2005;Ferrario-M ery et al, 2008), implying that the PII-mediated regulation of nitrite uptake by Arabidopsis chloroplasts is similar to that by cyanobacteria (Watzer et al, 2019). Further research identified WRINKLED1 as a transcription factor inducing AtGLB1 in Arabidopsis seeds at the onset of the maturation phase (Baud et al, 2010).…”

The Novel PII-Interacting Regulator PirC (Sll0944) Identifies 3-Phosphoglycerate Mutase (PGAM) as Central Control Point of Carbon Storage Metabolism in Cyanobacteria

“…In addition to the regulation of enzyme activities via PII, the trimeric protein can also influence transport activities. Recent pull-down analysis revealed that PII regulates an ensemble of nitrogen transport complexes, involving the NRT nitrate/nitrite transport system, the URT urea transport system and the ammonium transporter AMT1 through direct protein-protein interaction (12).…”

“…In a previous PII-pull down study, several putative PII interactors of unknown function had been identified (12). The most prominent among these was the product of the sll0944 gene, a member of the NtcA regulon (13).…”

Regulatory Diversity and Functional Analysis of Two-Component Systems in Cyanobacterium Synechocystis sp. PCC 6803 by GC-MS Based Metabolomics

“…Like in plants, serine biosynthesis in cyanobacteria involved light-dependent photo-respiratory and light-independent phosphoserine pathways (Klemke et al, 2015). The concentration of urea was also increased 1.67-folds than that of the wild type, in accordance with the up-regulation of several amino acids such as glycine in cyanobacteria (Esteves-Ferreira et al, 2018;Watzer et al, 2019). Three monosaccharides, including D-glucose involved in glycolysis process, methyl-Dgalactopyranoside and D-altrose were also up-regulated by more than 2.65-folds respective to the wild type, in line with the possible function of Sll1330 in glycolysis, which was revealed by a previous study that the knockout of sll1330 could cause the accretion of these monosaccharide (Tabei et al, 2007).…”