Spatial separation of the photosynthetic reactions is a key feature of C metabolism. In most C plants, this separation requires compartmentation of photosynthetic enzymes between mesophyll (M) and bundle sheath (BS) cells. The upstream region of the gene encoding the maize PHOSPHOENOLPYRUVATE CARBOXYLASE 1 (ZmPEPC1) has been shown sufficient to drive M-specific gene expression.
View Article and Find Full Text PDFCompartmentation of photosynthetic reactions between mesophyll and bundle sheath cells is a key feature of C photosynthesis and depends on the cell-specific accumulation of major C enzymes, such as phosphoenolpyruvate carboxylase 1. The ZmPEPC1 upstream region, which drives light-inducible and mesophyll-specific gene expression in maize, has been shown to keep the same properties when introduced into rice (C plant), indicating that rice has the transcription factors (TFs) needed to confer C -like gene expression. Using a yeast one-hybrid approach, we identified OsbHLH112, a rice basic Helix-Loop-Helix (bHLH) TF that interacts with the maize ZmPEPC1 upstream region.
View Article and Find Full Text PDFThe non-proteinogenic amino acid ornithine links several stress response pathways. From a previous study we know that ornithine accumulates in response to low CO2. To investigate ornithine accumulation in plants, we shifted plants to either low CO2 or low light.
View Article and Find Full Text PDFPhotorespiration is essential for the detoxification of glycolate and recycling of carbon to the Calvin Benson Bassham cycle. Enzymes participating in the pathway have been identified, and investigations now focus on the regulation of photorespiration by transporters and metabolites. However, regulation of photorespiration on the gene level has not been intensively studied.
View Article and Find Full Text PDFThe mitochondrial NADH dehydrogenase complex (complex I) is of particular importance for the respiratory chain in mitochondria. It is the major electron entry site for the mitochondrial electron transport chain (mETC) and therefore of great significance for mitochondrial ATP generation. We recently described an Arabidopsis thaliana double-mutant lacking the genes encoding the carbonic anhydrases CA1 and CA2, which both form part of a plant-specific 'carbonic anhydrase domain' of mitochondrial complex I.
View Article and Find Full Text PDFComplex I of the mitochondrial electron transport chain (mETC) in plants contains an extra domain that is made up from proteins homologous to prokaryotic gamma-carbonic anhydrases (γCA). This domain has been suggested to participate in complex I assembly or to support transport of mitochondrial CO2 to the chloroplast. Here, we generated mutants lacking CA1 and CA2 - two out of three CA proteins in Arabidopsis thaliana.
View Article and Find Full Text PDFThe mitochondrial NADH dehydrogenase complex (complex I) consists of several functional domains which independently arose during evolution. In higher plants, it contains an additional domain which includes proteins resembling gamma-type carbonic anhydrases. The Arabidopsis genome codes for five complex I-integrated gamma-type carbonic anhydrases (γCA1, γCA2, γCA3, γCAL1, γCAL2), but only three copies of this group of proteins form an individual extra domain.
View Article and Find Full Text PDFThe transition of C3 , via C2 towards C4 photosynthesis is an important example of stepwise evolution of a complex genetic trait. A common feature that was gradually emphasized during this trajectory is the evolution of a CO2 concentration mechanism around Rubisco. In C2 plants, this mechanism is based on tissue-specific accumulation of glycine decarboxylase (GDC) in bundle sheath (BS) cells, relative to global expression in the cells of C3 leaves.
View Article and Find Full Text PDF"Gamma-type carbonic anhydrase-like" (CAL) proteins form part of complex I in plants. Together with "gamma carbonic anhydrase" (CA) proteins they form an extra domain which is attached to the membrane arm of complex I on its matrix exposed side. In Arabidopsis two CAL and three CA proteins are present, termed CAL1, CAL2, CA1, CA2 and CA3.
View Article and Find Full Text PDFHistone modifications contribute to gene regulation in eukaryotes. We analyzed genome-wide histone H3 Lysine (Lys) 4 trimethylation and histone H3 Lys 9 acetylation (two modifications typically associated with active genes) in meristematic cells at the base and expanded cells in the blade of the maize (Zea mays) leaf. These data were compared with transcript levels of associated genes.
View Article and Find Full Text PDFCurr Opin Plant Biol
June 2014
Heterosis is the increase in fitness and yield of F1 hybrids derived from a cross between distantly related genotypes. The use of heterosis is one of the most successful crop breeding strategies, but the underlying molecular mechanisms are still poorly defined. There is ample evidence that heterosis is associated with increased rates of photosynthesis and recent analyses have shed light on the underlying biochemical principles.
View Article and Find Full Text PDFChlamydomonas reinhardtii contains a unique glycolate dehydrogenase (CrGlcDH) for glycolate oxidation in photorespiration that is different in structure from the GlcDH enzymes of heteroptrophic prokaryotes and the glycolate oxidases of higher plants. Here, we purified the recombinantly overexpressed enzyme and characterized its enzymatic properties. CrGlcDH uses D-lactate, but not l-lactate, as an alternative substrate with similar catalytic efficiency compared to glycolate.
View Article and Find Full Text PDFWe have increased the productivity and yield of potato (Solanum tuberosum) by developing a novel method to enhance photosynthetic carbon fixation based on expression of a polyprotein (DEFp) comprising all three subunits (D, E and F) of Escherichia coli glycolate dehydrogenase (GlcDH). The engineered polyprotein retained the functionality of the native GlcDH complex when expressed in E. coli and was able to complement mutants deficient for the D, E and F subunits.
View Article and Find Full Text PDFGlyoxylate is a peroxisomal intermediate of photorespiration, the recycling pathway for 2-phosphoglycolate (2-PG) produced by the oxygenase activity of Rubisco. Under hot and dry growth conditions, photorespiratory intermediates can accumulate and must be detoxified by alternative pathways, including plastidal reactions. Moreover, there is evidence that chloroplasts are capable of actively producing glyoxylate from glycolate.
View Article and Find Full Text PDFGene promoters perceive numerous signals and integrate this information into a single response, the transcriptional activity of a gene. It was speculated that covalent modification of histones on the promoters might have an important function in storage and integration of signals. Using the genes for the core proteins of C4 metabolism in maize as a model, we associated the perception of specific signals with the establishment of individual histone modifications.
View Article and Find Full Text PDFUnlabelled: Here, a first GelMap of the chloroplast "protein complex proteome" of Arabidopsis thaliana is presented. The GelMap software tool allows assigning multiple proteins to gel spots, thereby taking advantage of the high sensitivity of state-of-the-art mass spectrometry systems. Furthermore, the software allows functional annotation of all identified proteins.
View Article and Find Full Text PDFC4 photosynthesis evolved more than 60 times independently in different plant lineages. Each time, multiple genes were recruited into C4 metabolism. The corresponding promoters acquired new regulatory features such as high expression, light induction, or cell type-specific expression in mesophyll or bundle sheath cells.
View Article and Find Full Text PDFPhotorespiration has been suggested as a target for increasing photosynthesis for decades. Within the last few years, three bypass pathways or reactions have been designed and tested in plants. The three reactions bypass photorespiration either in the chloroplast or in the peroxisome, or oxidize glycolate completely to CO(2) in the chloroplast.
View Article and Find Full Text PDFIn most studies, amounts of protein complexes of the oxidative phosphorylation (OXPHOS) system in different organs or tissues are quantified on the basis of isolated mitochondrial fractions. However, yield of mitochondrial isolations might differ with respect to tissue type due to varying efficiencies of cell disruption during organelle isolation procedures or due to tissue-specific properties of organelles. Here we report an immunological investigation on the ratio of the OXPHOS complexes in different tissues of Arabidopsis thaliana which is based on total protein fractions isolated from five Arabidopsis organs (leaves, stems, flowers, roots and seeds) and from callus.
View Article and Find Full Text PDFThe major photorespiratory pathway in higher plants is distributed over chloroplasts, mitochondria, and peroxisomes. In this pathway, glycolate oxidation takes place in peroxisomes. It was previously suggested that a mitochondrial glycolate dehydrogenase (GlcDH) that was conserved from green algae lacking leaf-type peroxisomes contributes to photorespiration in Arabidopsis thaliana.
View Article and Find Full Text PDFSource and sink strength control plant carbon gain and yield. Source strength was recently engineered by modifying the large subunit of Rubisco, replacing the small subunit, and creating improved thermostable Rubisco activases. This technological breakthrough makes Rubisco engineering feasible at last.
View Article and Find Full Text PDFChromatin structure is important for the regulation of gene expression in eukaryotes. In this process, chromatin remodeling, DNA methylation, and covalent modifications on the amino-terminal tails of histones H3 and H4 play essential roles(1-2). H3 and H4 histone modifications include methylation of lysine and arginine, acetylation of lysine, and phosphorylation of serine residues(1-2).
View Article and Find Full Text PDFC(4) plants established a mechanism for the concentration of CO(2) in the vicinity of ribulose-1,5-bisphosphate carboxylase/oxygenase in order to saturate the enzyme with substrate and substantially to reduce the alternative fixation of O(2) that results in energy losses. Transfer of the C(4) mechanism to C(3) plants has been repeatedly tested, but none of the approaches so far resulted in transgenic plants with enhanced photosynthesis or growth. Instead, often deleterious effects were observed.
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