The Chlamydomonas reinhardtii transcription factor PSR1 is required for the control of activities involved in scavenging phosphate from the environment during periods of phosphorus limitation. Increased scavenging activity reflects the development of high-affinity phosphate transport and the expression of extracellular phosphatases that can cleave phosphate from organic compounds in the environment. A comparison of gene expression patterns using microarray analyses and quantitative PCRs with wild-type and psr1 mutant cells deprived of phosphorus has revealed that PSR1 also controls genes encoding proteins with potential "electron valve" functions--these proteins can serve as alternative electron acceptors that help prevent photodamage caused by overexcitation of the photosynthetic electron transport system. In accordance with this finding, phosphorus-starved psr1 mutants die when subjected to elevated light intensities; at these intensities, the wild-type cells still exhibit rapid growth. Acclimation to phosphorus deprivation also involves a reduction in the levels of transcripts encoding proteins involved in photosynthesis and both cytoplasmic and chloroplast translation as well as an increase in the levels of transcripts encoding stress-associated chaperones and proteases. Surprisingly, phosphorus-deficient psr1 cells (but not wild-type cells) also display expression patterns associated with specific responses to sulfur deprivation, suggesting a hitherto unsuspected link between the signal transduction pathways involved in controlling phosphorus and sulfur starvation responses. Together, these results demonstrate that PSR1 is critical for the survival of cells under conditions of suboptimal phosphorus availability and that it plays a key role in controlling both scavenging responses and the ability of the cell to manage excess absorbed excitation energy.
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http://dx.doi.org/10.1128/EC.5.1.26-44.2006 | DOI Listing |
Plant Sci
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Instituto de Fisiología Vegetal (INFIVE CCT CONICET La Plata), Universidad Nacional de La Plata (UNLP) y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Diagonal 113 Nº 495, La Plata 1900, Argentina. Electronic address:
Nitrate reductase (NR) is an essential enzyme because of its role in nitrogen metabolism and in key signaling events through the generation of the reactive nitrogen species, nitric oxide (NO). In this work, we evaluated changes in endogenous NO levels during the onset of P-restriction in soybean plants (Glycine max), focusing on the possible pathways involved in its generation, namely NR and NO synthase like activity, NOS, and the subsequent role of NR during low P-acclimation. During the first 96 h of P-starvation NO levels increased in the leaves.
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Natural History Museum, Cromwell Road, SW7 5BD, London, UK.
Phyllosilicates provide a primary source of minerals used by microorganisms and plants, particularly clay minerals, i.e., phyllosilicates of very small particle size.
View Article and Find Full Text PDFPlants (Basel)
October 2024
Department of Agricultural Sciences, University of Naples Federico II, Via Università 100, Portici, 80055 Naples, Italy.
The by-products of the extraction of sea buckthorn ( L.) concentrated juice may represent a functional food ingredient for white chocolate production, as a rich source of bioactive compounds. The effects of six treatments derived from the factorial combination of two types of by-products (with oil or without oil) and three different concentrations (5%, 10%, and 15%), were assessed on rheological, quality, colour, antioxidant, and mineral properties of chocolate.
View Article and Find Full Text PDFJ Biol Chem
October 2024
Department of Medico-Surgical Sciences and Biotechnologies, Sapienza University of Rome, Latina, Italy. Electronic address:
Desmethylphosphinothricin (L-Glu-γ-P) is the H-phosphinic analog of glutamate with carbon-phosphorus-hydrogen (C-P-H) bonds. In L-Glu-γ-P the phosphinic group acts as a bioisostere of the glutamate γ-carboxyl group allowing the molecule to be a substrate of Escherichia coli glutamate decarboxylase, a pyridoxal 5'-phosphate-dependent α-decarboxylase. In addition, the L-Glu-γ-P decarboxylation product, GABA-P, is further metabolized by bacterial GABA-transaminase, another pyridoxal 5'-phosphate-dependent enzyme, and succinic semialdehyde dehydrogenase, a NADP-dependent enzyme.
View Article and Find Full Text PDFInt J Phytoremediation
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Department of Ecology and Environmental Science, Assam University, Silchar, Assam, India.
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