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Trends in Plant Science Oct 2019Protein amino (N) termini are major determinants of protein stability in the cytosol of eukaryotes and prokaryotes, conceptualized in the N-end rule pathway, lately... (Review)
Review
Protein amino (N) termini are major determinants of protein stability in the cytosol of eukaryotes and prokaryotes, conceptualized in the N-end rule pathway, lately referred to as N-degron pathways. Here we argue for the existence of N-degron pathways in plastids of apicomplexa, algae, and plants. The prokaryotic N-degron pathway depends on a caseinolytic protease (CLP) S recognin (adaptor) for the recognition and delivery of N-degron-bearing substrates to CLP chaperone-protease systems. Diversified CLP systems are found in chloroplasts and nonphotosynthetic plastids, including CLPS homologs that specifically interact with a subset of N-terminal residues and stromal proteins. Chloroplast N-terminome data show enrichment of classic stabilizing residues [Ala (A), Ser (S), Val (V), Thr (T)] and avoidance of charged and large hydrophobic residues. We outline experimental test strategies for plastid N-degron pathways.
Topics: Chloroplasts; Endopeptidase Clp; Plastids
PubMed: 31300194
DOI: 10.1016/j.tplants.2019.06.013 -
Methods in Molecular Biology (Clifton,... 2018Plastids are semiautonomous organelles like mitochondria, and derive from a cyanobacterial ancestor that was engulfed by a host cell. During evolution, they have... (Review)
Review
Plastids are semiautonomous organelles like mitochondria, and derive from a cyanobacterial ancestor that was engulfed by a host cell. During evolution, they have recruited proteins originating from the nuclear genome, and only parts of their ancestral metabolic properties were conserved and optimized to limit functional redundancy with other cell compartments. Furthermore, large disparities in metabolic functions exist among various types of plastids, and the characterization of their various metabolic properties is far from being accomplished. In this review, we provide an overview of the main functions, known to be achieved by plastids or shared by plastids and other compartments of the cell. In short, plastids appear at the heart of all main plant functions.
Topics: Biological Evolution; Energy Metabolism; Plastids
PubMed: 29987715
DOI: 10.1007/978-1-4939-8654-5_5 -
Plant Cell Reports Jul 2023Novel episomal systems have the potential to accelerate plastid genetic engineering for application in plant synthetic biology. Plastids represent valuable subcellular... (Review)
Review
Novel episomal systems have the potential to accelerate plastid genetic engineering for application in plant synthetic biology. Plastids represent valuable subcellular compartments for genetic engineering of plants with intrinsic advantages to engineering the nucleus. The ability to perform site-specific transgene integration by homologous recombination (HR), coordination of transgene expression in operons, and high production of heterologous proteins, all make plastids an attractive target for synthetic biology. Typically, plastid engineering is performed by homologous recombination; however, episomal-replicating vectors have the potential to accelerate the design/build/test cycles for plastid engineering. By accelerating the timeline from design to validation, it will be possible to generate translational breakthroughs in fields ranging from agriculture to biopharmaceuticals. Episomal-based plastid engineering will allow precise single step metabolic engineering in plants enabling the installation of complex synthetic circuits with the ambitious goal of reaching similar efficiency and flexibility of to the state-of-the-art genetic engineering of prokaryotic systems. The prospect to design novel episomal systems for production of transplastomic marker-free plants will also improve biosafety for eventual release in agriculture.
Topics: Genetic Engineering; Plastids; Plants; Transgenes; Metabolic Engineering; DNA; Plants, Genetically Modified; Transformation, Genetic
PubMed: 37127835
DOI: 10.1007/s00299-023-03020-x -
Plant Physiology Feb 2014Starch is a biologically and commercially important polymer of glucose and is synthesized to form starch grains (SGs) inside amyloplasts. Cereal endosperm accumulates...
Starch is a biologically and commercially important polymer of glucose and is synthesized to form starch grains (SGs) inside amyloplasts. Cereal endosperm accumulates starch to levels that are more than 90% of the total weight, and most of the intracellular space is occupied by SGs. The size of SGs differs depending on the plant species and is one of the most important factors for industrial applications of starch. However, the molecular machinery that regulates the size of SGs is unknown. In this study, we report a novel rice (Oryza sativa) mutant called substandard starch grain4 (ssg4) that develops enlarged SGs in the endosperm. Enlargement of SGs in ssg4 was also observed in other starch-accumulating tissues such as pollen grains, root caps, and young pericarps. The SSG4 gene was identified by map-based cloning. SSG4 encodes a protein that contains 2,135 amino acid residues and an amino-terminal amyloplast-targeted sequence. SSG4 contains a domain of unknown function490 that is conserved from bacteria to higher plants. Domain of unknown function490-containing proteins with lengths greater than 2,000 amino acid residues are predominant in photosynthetic organisms such as cyanobacteria and higher plants but are minor in proteobacteria. The results of this study suggest that SSG4 is a novel protein that influences the size of SGs. SSG4 will be a useful molecular tool for future starch breeding and biotechnology.
Topics: Amino Acid Sequence; Chloroplasts; Chromosome Segregation; Cloning, Molecular; Crosses, Genetic; Endosperm; Gene Expression Regulation, Plant; Genes, Plant; Genetic Complementation Test; Green Fluorescent Proteins; Molecular Sequence Data; Mutation; Organ Specificity; Oryza; Physical Chromosome Mapping; Plant Proteins; Plants, Genetically Modified; Plastids; Pollen; Starch; Subcellular Fractions
PubMed: 24335509
DOI: 10.1104/pp.113.229591 -
Methods in Molecular Biology (Clifton,... 2024Plastids are semi-autonomous organelles like mitochondria and derive from a cyanobacterial ancestor that was engulfed by a host cell. During evolution, they have... (Review)
Review
Plastids are semi-autonomous organelles like mitochondria and derive from a cyanobacterial ancestor that was engulfed by a host cell. During evolution, they have recruited proteins originating from the nuclear genome, and only parts of their ancestral metabolic properties were conserved and optimized to limit functional redundancy with other cell compartments. Furthermore, large disparities in metabolic functions exist among various types of plastids, and the characterization of their various metabolic properties is far from being accomplished. In this review, we provide an overview of the main functions, known to be achieved by plastids or shared by plastids and other compartments of the cell. In short, plastids appear at the heart of all main plant functions.
Topics: Plastids; Mitochondria
PubMed: 38502499
DOI: 10.1007/978-1-0716-3726-5_5 -
Protoplasma Nov 2018Land plants perceive gravity and respond to it in an organ-specific way; shoots typically direct growth upwards, roots typically downwards. Historically, at least with...
Land plants perceive gravity and respond to it in an organ-specific way; shoots typically direct growth upwards, roots typically downwards. Historically, at least with respect to maize plants, this phenomenon is attributed to three sequential processes, namely graviperception, the transduction of the perceived signal, and the graviresponse, resulting in a typical (re)positioning of the organ or entire plant body relative to the gravivector. For decades, sedimentation of starch-containing plastids within the cells of special tissues has been regarded as the primary and initiating process fundamental for gravitropic growth (starch-statolith hypothesis). Based on Popper's falsification principle, uncompromising experiments were executed. The results indicate that the model of graviperception based on amyloplast sedimentation does not apply to maize seedlings.
Topics: Germination; Gravitropism; Gravity Sensing; Image Processing, Computer-Assisted; Plant Roots; Plastids; Seedlings; Zea mays
PubMed: 29948366
DOI: 10.1007/s00709-018-1272-7 -
Trends in Plant Science Feb 2014In structural, functional, and evolutionary terms, galactoglycerolipids are signature lipids of chloroplasts. Their presence in nongreen plastids has been demonstrated... (Review)
Review
In structural, functional, and evolutionary terms, galactoglycerolipids are signature lipids of chloroplasts. Their presence in nongreen plastids has been demonstrated in angiosperms and diatoms. Thus, galactoglycerolipids are considered as a landmark of green and nongreen plastids, deriving from either a primary or secondary endosymbiosis. The discovery of a plastid in Plasmodium falciparum, the causative agent of malaria, fueled the search for galactoglycerolipids as possible targets for treatments. However, recent data have provided evidence that the Plasmodium plastid does not contain any galactoglycerolipids. In this opinion article, we discuss questions raised by the loss of galactoglycerolipids during evolution: how have galactoglycerolipids been lost? How does the Plasmodium plastid maintain four membranes without these lipids? What are the main constituents instead of galactoglycerolipids?
Topics: Galactolipids; Plasmodium; Plastids
PubMed: 24231068
DOI: 10.1016/j.tplants.2013.10.004 -
Cell Reports Sep 2020The role of amyloplasts in the interactions between hydrotropism and gravitropism has been previously described. However, the effect of light-dark on the interactions...
The role of amyloplasts in the interactions between hydrotropism and gravitropism has been previously described. However, the effect of light-dark on the interactions between the two tropisms remains unclear. Here, by developing a method that makes it possible to mimic natural conditions more closely than the conventional lab conditions, we show that hydrotropism is higher in wild-type Arabidopsis seedlings whose shoots are illuminated but whose roots are grown in the dark compared with seedlings that are fully exposed to light. Root gravitropism is substantially decreased because of the reduction of amyloplast content in the root tip with decreased gene expression in PGM1 (a key starch biosynthesis gene), which may contribute to enhanced root hydrotropism under darkness. Furthermore, the starch-deficient mutant pgm1-1 exhibits greater hydrotropism compared with wild-type. Our results suggest that amyloplast response and starch reduction occur under light-dark modulation, followed by decreased gravitropism and enhanced hydrotropism in Arabidopsis root.
Topics: Arabidopsis; Gravitropism; Plant Roots; Plastids; Tropism
PubMed: 32997985
DOI: 10.1016/j.celrep.2020.108198 -
Plant Biotechnology Journal Mar 2022Starch accounts for over 80% of the total dry weight in cereal endosperm and determines the kernel texture and nutritional quality. Amyloplasts, terminally...
Starch accounts for over 80% of the total dry weight in cereal endosperm and determines the kernel texture and nutritional quality. Amyloplasts, terminally differentiated plastids, are responsible for starch biosynthesis and storage. We screened a series of rice mutants with floury endosperm to clarify the mechanism underlying amyloplast development and starch synthesis. We identified the floury endosperm19 (flo19) mutant which shows opaque of the interior endosperm. Abnormal compound starch grains (SGs) were present in the endosperm cells of the mutant. Molecular cloning revealed that the FLO19 allele encodes a plastid-localized pyruvate dehydrogenase complex E1 component subunit α1 (ptPDC-E1-α1) that is expressed in all rice tissues. In vivo enzyme assays demonstrated that the flo19 mutant showed decreased activity of the plastidic pyruvate dehydrogenase complex. In addition, the amounts of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) were much lower in the developing flo19 mutant endosperm, suggesting that FLO19 participates in fatty acid supply for galactolipid biosynthesis in amyloplasts. FLO19 overexpression significantly increased seed size and weight, but did not affect other important agronomic traits, such as panicle length, tiller number and seed setting rate. An analysis of single nucleotide polymorphism data from a panel of rice accessions identified that the pFLO19 haplotype was positively associated with grain length, implying a potential application in rice breeding. In summary, our study demonstrates that FLO19 is involved in galactolipid biosynthesis which is essential for amyloplast development and starch biosynthesis in rice.
Topics: Edible Grain; Endosperm; Galactolipids; Gene Expression Regulation, Plant; Mutation; Oryza; Plant Breeding; Plant Proteins; Plastids; Pyruvate Dehydrogenase Complex; Starch
PubMed: 34655511
DOI: 10.1111/pbi.13727 -
Methods in Molecular Biology (Clifton,... 2022Studying the stability of a protein dependent on its N-terminal residue requires a mechanism, which selectively exposes the amino acid at the N-terminus. Here, we...
Studying the stability of a protein dependent on its N-terminal residue requires a mechanism, which selectively exposes the amino acid at the N-terminus. Here, we describe the use of the tobacco etch virus (TEV) protease to generate a specific N-terminal amino acid in the stroma of the chloroplast. The established molecular reporter system further allows the quantification of the reporter protein half-life dependent on the identity of the N-terminal residue.
Topics: Amino Acids; Chloroplasts; Plastids; Proteins
PubMed: 35188662
DOI: 10.1007/978-1-0716-1791-5_10