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Molecular Plant Dec 2023
Topics: Gravity Sensing; Gravitropism; Arabidopsis; Plastids; Plants
PubMed: 37919895
DOI: 10.1016/j.molp.2023.11.001 -
Plant Physiology Mar 2016Starch is a biologically and commercially important polymer of glucose. Starch is organized into starch grains (SGs) inside amyloplasts. The SG size differs depending on...
Starch is a biologically and commercially important polymer of glucose. Starch is organized into starch grains (SGs) inside amyloplasts. The SG size differs depending on the plant species and is one of the most important factors for industrial applications of starch. There is limited information on genetic factors regulating SG sizes. In this study, we report the rice (Oryza sativa) mutant substandard starch grain6 (ssg6), which develops enlarged SGs in endosperm. Enlarged SGs are observed starting at 3 d after flowering. During endosperm development, a number of smaller SGs appear and coexist with enlarged SGs in the same cells. The ssg6 mutation also affects SG morphologies in pollen. The SSG6 gene was identified by map-based cloning and microarray analysis. SSG6 encodes a protein homologous to aminotransferase. SSG6 differs from other rice homologs in that it has a transmembrane domain. SSG6-green fluorescent protein is localized in the amyloplast membrane surrounding SGs in rice endosperm, pollen, and pericarp. The results of this study suggest that SSG6 is a novel protein that controls SG size. SSG6 will be a useful molecular tool for future starch breeding and applications.
Topics: Amino Acid Sequence; Base Sequence; Cytoplasmic Granules; Endosperm; Gene Expression Regulation, Plant; Green Fluorescent Proteins; Immunoblotting; Intracellular Membranes; Membrane Proteins; Microscopy, Confocal; Microscopy, Electron, Transmission; Mutation; Oligonucleotide Array Sequence Analysis; Oryza; Plant Proteins; Plastids; Pollen; Sequence Homology, Amino Acid; Starch; Transaminases
PubMed: 26792122
DOI: 10.1104/pp.15.01811 -
Protoplasma Oct 2011Parasites like malaria and Toxoplasma possess a vestigial plastid homologous to the chloroplasts of plants. The plastid (known as the apicoplast) is non-photosynthetic... (Review)
Review
Parasites like malaria and Toxoplasma possess a vestigial plastid homologous to the chloroplasts of plants. The plastid (known as the apicoplast) is non-photosynthetic but retains many hallmarks of its ancestry including a circular genome that it synthesises proteins from and a suite of biosynthetic pathways of cyanobacterial origin. In this review, the discovery of the apicoplast and its integration, function and purpose are explored. New insights into the apicoplast fatty acid biosynthesis pathway and some novel roles of the apicoplast in vaccine development are reviewed.
Topics: Antiprotozoal Agents; Apicomplexa; Fatty Acids; Immunity; Intracellular Membranes; Microscopy, Electron, Transmission; Plastids; Protein Transport; Protozoan Infections; Symbiosis
PubMed: 21165662
DOI: 10.1007/s00709-010-0250-5 -
Current Opinion in Plant Biology Apr 2022The plastid (chloroplast) genome of seed plants represents an attractive target of metabolic pathway engineering by genetic transformation. Although the plastid genome... (Review)
Review
The plastid (chloroplast) genome of seed plants represents an attractive target of metabolic pathway engineering by genetic transformation. Although the plastid genome is relatively small, it can accommodate large amounts of foreign DNA that precisely integrates via homologous recombination, and is largely excluded from pollen transmission due to the maternal mode of plastid inheritance. Since the engineering of metabolic pathways often requires the expression of multiple transgenes, the possibility to conveniently stack transgenes in synthetic operons makes the transplastomic technology particularly appealing in the area of metabolic engineering. Absence of epigenetic gene silencing mechanisms from plastids and the possibility to achieve high transgene expression levels further add to the attractiveness of plastid genome transformation. This review focuses on engineering principles and available tools for the transplastomic expression of enzymes and pathways, and highlights selected recent applications in metabolic engineering.
Topics: Chloroplasts; Genetic Engineering; Metabolic Engineering; Plants, Genetically Modified; Plastids; Transgenes
PubMed: 35183927
DOI: 10.1016/j.pbi.2022.102185 -
Nature Communications Oct 2020The mechanism that creates vitreous endosperm in the mature maize kernel is poorly understood. We identified Vitreous endosperm 1 (Ven1) as a major QTL influencing this...
The mechanism that creates vitreous endosperm in the mature maize kernel is poorly understood. We identified Vitreous endosperm 1 (Ven1) as a major QTL influencing this process. Ven1 encodes β-carotene hydroxylase 3, an enzyme that modulates carotenoid composition in the amyloplast envelope. The A619 inbred contains a nonfunctional Ven1 allele, leading to a decrease in polar and an increase in non-polar carotenoids in the amyloplast. Coincidently, the stability of amyloplast membranes is increased during kernel desiccation. The lipid composition in endosperm cells in A619 is altered, giving rise to a persistent amyloplast envelope. These changes impede the gathering of protein bodies and prevent them from interacting with starch grains, creating air spaces that cause an opaque kernel phenotype. Genetic modifiers were identified that alter the effect of Ven1, while maintaining a high β-carotene level. These studies provide insight for breeding vitreous kernel varieties and high vitamin A content in maize.
Topics: Alleles; Carotenoids; Chromosome Mapping; Crosses, Genetic; Endosperm; Genes, Plant; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Mixed Function Oxygenases; Phenotype; Plant Breeding; Plant Proteins; Plastids; Quantitative Trait Loci; Seeds; Zea mays
PubMed: 33093471
DOI: 10.1038/s41467-020-19196-9 -
Protoplasma Jan 2015
Topics: Green Fluorescent Proteins; Plant Cells; Plastids
PubMed: 25572708
DOI: 10.1007/s00709-014-0745-6 -
Philosophical Transactions of the Royal... Oct 2000The term 'chlororespiration' is used to describe the activity of a putative respiratory electron transler chain within the thylakoid membrane of chloroplasts and was... (Review)
Review
The term 'chlororespiration' is used to describe the activity of a putative respiratory electron transler chain within the thylakoid membrane of chloroplasts and was originally proposed by Bennouon in 1982 to explain effects on the redox state of the plastoquinone pool in green algae in the absence of photosynthetic plastoquinone electrontransfer. In his original model, Bennoun suggested that the pool could be reduced through the action of a NAD(P) H dehydrogenase and could be oxidized by oxygen at an oxidase. At the same time an electrochemical gradient would be generated across the membrane. This review describes the current status of the chlororespiration model in light of the recent discoveries of novel respiratory components chloroplast thylakoid membrane.
Topics: Animals; Chlamydomonas reinhardtii; Chloroplasts; Electron Transport; Mitochondria; Models, Biological; Oxidoreductases; Plants; Plastids; Signal Transduction; Thylakoids
PubMed: 11128007
DOI: 10.1098/rstb.2000.0714 -
American Journal of Botany Dec 1986Amyloplast sedimentation during gravistimulation and organelle movements was studied in living central rootcap cells of Zea mays L. cv. Merit. Cells from sectioned roots...
Amyloplast sedimentation during gravistimulation and organelle movements was studied in living central rootcap cells of Zea mays L. cv. Merit. Cells from sectioned roots were viewed with a horizontally-mounted videomicroscope. The kinetics of gravity-induced amyloplast sedimentation were comparable to those calculated from experiments using fixed material. Individual amyloplasts fell at an average velocity of 5.5 micrometers min-1; the maximal velocity of fall measured was 18.0 micrometers min-1. Amyloplasts often rotated, sometimes rose in the cytoplasm, and occasionally underwent sudden rapid movements as fast as 58 micrometers min-1. Saltations of other organelles were frequently observed. This appears to be the first report of cytoplasmic streaming in the presumptive statocytes of roots.
Topics: Cytoplasmic Streaming; Gravitation; Gravity Sensing; Microscopy, Electron; Organelles; Plant Root Cap; Plastids; Zea mays
PubMed: 11538871
DOI: No ID Found -
Plant & Cell Physiology Dec 2002When cytokinin-autonomous tobacco BY-2 cell cultures are transferred into 2,4-dichlorophenoxyacetic acid (2,4-D)-deprived medium, amyloplast development is initiated....
When cytokinin-autonomous tobacco BY-2 cell cultures are transferred into 2,4-dichlorophenoxyacetic acid (2,4-D)-deprived medium, amyloplast development is initiated. Using this in vitro amyloplast-inducing system, the role of cytokinins in amyloplast formation was investigated. We show that addition of lovastatin, an inhibitor of mevalonate synthesis, to amyloplast-inducing medium reduced starch accumulation. Microscopic observation also revealed that lovastatin treatment decreased starch deposition; however, the overall morphologies of cells and plastids were less affected than control cell cultures. In addition, lovastatin lowered the transcription level of the ADP-glucose pyrophosphorylase small subunit (AgpS) gene. Application of mevalonate or zeatin dramatically restored the decrease in starch deposition, and restored AgpS mRNA accumulation. Moreover, addition of other molecules with cytokinin activity, such as adenine- and phenylurea-type compounds, restored starch accumulation and AgpS transcript levels, whereas other isopentenyl pyrophosphate-derived phytohormones did not. Liquid chromatography-mass spectrometry/mass spectrometry quantification of endogenous cytokinins revealed that endogenous cytokinins increased when BY-2 cells were transferred into 2,4-D-deprived medium from conventional medium containing 2,4-D. In addition, lovastatin treatment decreased endogenous cytokinins to some extent when cultured under 2,4-D-deprived conditions. Our results suggest that both 2,4-D deprivation and an increase in endogenous cytokinins have important roles in accelerating the changes in plastid morphology, starch accumulation, and AgpS gene expression.
Topics: 2,4-Dichlorophenoxyacetic Acid; Adenine; Adenosine; Benzyl Compounds; Cells, Cultured; Cytokinins; Gene Expression Regulation; Glucose-1-Phosphate Adenylyltransferase; Hemiterpenes; Isopentenyladenosine; Kinetin; Lovastatin; Mass Spectrometry; Mevalonic Acid; Nucleotidyltransferases; Organophosphorus Compounds; Plant Growth Regulators; Plastids; Purines; RNA, Messenger; Starch; Nicotiana; Zeatin
PubMed: 12514251
DOI: 10.1093/pcp/pcf173 -
Nature Reviews. Microbiology Jun 2024
Topics: Organelles; Plastids
PubMed: 38658788
DOI: 10.1038/s41579-024-01053-x