Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The first molecular and genetic characterization of a biochemical pathway for oxidation of the reduced phosphorus (P) compounds phosphite and hypophosphite is reported. The pathway was identified in Pseudomonas stutzeri WM88, which was chosen for detailed studies from a group of organisms isolated based on their ability to oxidize hypophosphite (+1 valence) and phosphite (+3 valence) to phosphate (+5 valence). The genes required for oxidation of both compounds by P. stutzeri WM88 were cloned on a single ca. 30-kbp DNA fragment by screening for expression in Escherichia coli and Pseudomonas aeruginosa. Two lines of evidence suggest that hypophosphite is oxidized to phosphate via a phosphite intermediate. First, plasmid subclones that conferred oxidation of phosphite, but not hypophosphite, upon heterologous hosts were readily obtained. All plasmid subclones that failed to confer phosphite oxidation also failed to confer hypophosphite oxidation. No subclones that conferred only hypophosphite expression were obtained. Second, various deletion derivatives of the cloned genes were made in vitro and recombined onto the chromosome of P. stutzeri WM88. Two phenotypes were displayed by individual mutants. Mutants with the region encoding phosphite oxidation deleted (based upon the subcloning results) lost the ability to oxidize either phosphite or hypophosphite. Mutants with the region encoding hypophosphite oxidation deleted lost only the ability to oxidize hypophosphite. The phenotypes displayed by these mutants also demonstrate that the cloned genes are responsible for the P oxidation phenotypes displayed by the original P. stutzeri WM88 isolate. The DNA sequences of the minimal regions implicated in oxidation of each compound were determined. The region required for oxidation of phosphite to phosphate putatively encodes a binding-protein-dependent phosphite transporter, an NAD+-dependent phosphite dehydrogenase, and a transcriptional activator of the lysR family. The region required for oxidation of hypophosphite to phosphite putatively encodes a binding-protein-dependent hypophosphite transporter and an alpha-ketoglutarate-dependent hypophosphite dioxygenase. The finding of genes dedicated to oxidation of reduced P compounds provides further evidence that a redox cycle for P may be important in the metabolism of this essential, and often growth-limiting, nutrient.
 ...
PMID:Molecular genetic analysis of phosphite and hypophosphite oxidation by Pseudomonas stutzeri WM88. 979 Nov 2

Phosphorus (P) is an essential macronutrient for all living organisms and limits plant growth. Four proteins comprising a single SYG1/Pho81/XPR1 (SPX) domain, SPX1 to SPX4, are putative phosphate-dependent inhibitors of Arabidopsis (Arabidopsis thaliana) PHOSPHATE STARVATION RESPONSE1 (PHR1), the master transcriptional activator of phosphate starvation responses. This work demonstrated that SPX4 functions as a negative regulator not only of PHR1-dependent but also of PHR1-independent responses in P-replete plants. Transcriptomes of P-limited spx4 revealed that, unlike SPX1 and SPX2, SPX4 modulates the shoot phosphate starvation response but not short-term recovery after phosphate resupply. In roots, transcriptional regulation of P status is SPX4 independent. Genes misregulated in spx4 shoots intersect with both PHR1-dependent and PHOSPHATE2-dependent signaling networks associated with plant development, senescence, and ion/metabolite transport. Gene regulatory network analyses suggested that SPX4 interacts with transcription factors other than PHR1, such as SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 and ARABIDOPSIS NAC DOMAIN CONTAINING PROTEIN55, known regulators of shoot development. Transient expression studies in protoplasts indicated that PHR1 retention in the cytosol by SPX4 occurs in a dose- and P-status-dependent manner. Using a luciferase reporter in vivo, SPX4 expression kinetics and stability revealed that SPX4 is a short-lived protein with P-status-dependent turnover. SPX4 protein levels were quickly restored by phosphate resupply to P-limited plants. Unlike its monocot ortholog, AtSPX4 was not stabilized by the phosphate analog phosphite, implying that intracellular P status is sensed by its SPX domain via phosphate-rich metabolite signals.
 ...
PMID:SPX4 Acts on PHR1-Dependent and -Independent Regulation of Shoot Phosphorus Status in Arabidopsis. 3126 54