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Cell Oct 2023Gravity controls directional growth of plants, and the classical starch-statolith hypothesis proposed more than a century ago postulates that amyloplast sedimentation in...
Gravity controls directional growth of plants, and the classical starch-statolith hypothesis proposed more than a century ago postulates that amyloplast sedimentation in specialized cells initiates gravity sensing, but the molecular mechanism remains uncharacterized. The LAZY proteins are known as key regulators of gravitropism, and lazy mutants show striking gravitropic defects. Here, we report that gravistimulation by reorientation triggers mitogen-activated protein kinase (MAPK) signaling-mediated phosphorylation of Arabidopsis LAZY proteins basally polarized in root columella cells. Phosphorylation of LAZY increases its interaction with several translocons at the outer envelope membrane of chloroplasts (TOC) proteins on the surface of amyloplasts, facilitating enrichment of LAZY proteins on amyloplasts. Amyloplast sedimentation subsequently guides LAZY to relocate to the new lower side of the plasma membrane in columella cells, where LAZY induces asymmetrical auxin distribution and root differential growth. Together, this study provides a molecular interpretation for the starch-statolith hypothesis: the organelle-movement-triggered molecular polarity formation.
Topics: Arabidopsis; Arabidopsis Proteins; Gravity Sensing; Plant Roots; Plastids; Starch; Membrane Proteins
PubMed: 37741279
DOI: 10.1016/j.cell.2023.09.014 -
Protoplasma Jan 2024
Topics: Plastids
PubMed: 38102506
DOI: 10.1007/s00709-023-01913-y -
Current Biology : CB Jun 2019Mitochondria, a nearly ubiquitous feature of eukaryotes, are derived from an ancient symbiosis. Despite billions of years of cooperative coevolution - in what is... (Review)
Review
Mitochondria, a nearly ubiquitous feature of eukaryotes, are derived from an ancient symbiosis. Despite billions of years of cooperative coevolution - in what is arguably the most important mutualism in the history of life - the persistence of mitochondrial genomes also creates conditions for genetic conflict with the nucleus. Because mitochondrial genomes are present in numerous copies per cell, they are subject to both within- and among-organism levels of selection. Accordingly, 'selfish' genotypes that increase their own proliferation can rise to high frequencies even if they decrease organismal fitness. It has been argued that uniparental (often maternal) inheritance of cytoplasmic genomes evolved to curtail such selfish replication by minimizing within-individual variation and, hence, within-individual selection. However, uniparental inheritance creates conditions for cytonuclear conflict over sex determination and sex ratio, as well as conditions for sexual antagonism when mitochondrial variants increase transmission by enhancing maternal fitness but have the side-effect of being harmful to males (i.e., 'mother's curse'). Here, we review recent advances in understanding selfish replication and sexual antagonism in the evolution of mitochondrial genomes and the mechanisms that suppress selfish interactions, drawing parallels and contrasts with other organelles (plastids) and bacterial endosymbionts that arose more recently. Although cytonuclear conflict is widespread across eukaryotes, it can be cryptic due to nuclear suppression, highly variable, and lineage-specific, reflecting the diverse biology of eukaryotes and the varying architectures of their cytoplasmic genomes.
Topics: Bacterial Physiological Phenomena; Biological Evolution; Eukaryota; Genome, Mitochondrial; Plastids; Symbiosis
PubMed: 31163164
DOI: 10.1016/j.cub.2019.03.020 -
Current Biology : CB Apr 2018de Vries and Archibald introduce the topic of plastid genomes - prokaryotic genomes housed within eukaryotic algae and plants. (Review)
Review
de Vries and Archibald introduce the topic of plastid genomes - prokaryotic genomes housed within eukaryotic algae and plants.
Topics: Cyanobacteria; Evolution, Molecular; Genome, Plastid; Phylogeny; Plants; Plastids; Symbiosis
PubMed: 29689202
DOI: 10.1016/j.cub.2018.01.027 -
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 -
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 -
Science (New York, N.Y.) Sep 2023Organisms have evolved under gravitational force, and many sense the direction of gravity by means of statoliths in specialized cells. In flowering plants,...
Organisms have evolved under gravitational force, and many sense the direction of gravity by means of statoliths in specialized cells. In flowering plants, starch-accumulating plastids, known as amyloplasts, act as statoliths to facilitate downstream gravitropism. The gravity-sensing mechanism has long been considered a mechanosensing process by which amyloplasts transmit forces to intracellular structures, but the molecular mechanism underlying this has not been elucidated. We show here that LAZY1-LIKE (LZY) family proteins involved in statocyte gravity signaling associate with amyloplasts and the proximal plasma membrane. This results in polar localization according to the direction of gravity. We propose a gravity-sensing mechanism by which LZY translocation to the plasma membrane signals the direction of gravity by transmitting information on the position of amyloplasts.
Topics: Humans; Cell Membrane; Cell Polarity; Gravitation; Gravitropism; Gravity Sensing; Plastids; Protein Transport; Arabidopsis Proteins; Arabidopsis
PubMed: 37561884
DOI: 10.1126/science.adh9978 -
Biochimica Et Biophysica Acta Sep 2015Progress in the field of regulated intramembrane proteolysis (RIP) in recent years has not surpassed plant biology. Nevertheless, reports on RIP in plants, and... (Review)
Review
Progress in the field of regulated intramembrane proteolysis (RIP) in recent years has not surpassed plant biology. Nevertheless, reports on RIP in plants, and especially in chloroplasts, are still scarce. Of the four different families of intramembrane proteases, only two have been linked to chloroplasts so far, rhomboids and site-2 proteases (S2Ps). The lack of chloroplast-located rhomboid proteases was associated with reduced fertility and aberrations in flower morphology, probably due to perturbations in jasmonic acid biosynthesis, which occurs in chloroplasts. Mutations in homologues of S2P resulted in chlorophyll deficiency and impaired chloroplast development, through a yet unknown mechanism. To date, the only known substrate of RIP in chloroplasts is a PHD transcription factor, located in the envelope. Upon proteolytic cleavage by an unknown protease, the soluble N-terminal domain of this protein is released from the membrane and relocates to the nucleus, where it activates the transcription of the ABA response gene ABI4. Continuing studies on these proteases and substrates, as well as identification of the genes responsible for different chloroplast mutant phenotypes, are expected to shed more light on the roles of intramembrane proteases in chloroplast biology.
Topics: Membrane Proteins; Peptide Hydrolases; Plastids; Proteolysis
PubMed: 25528366
DOI: 10.1016/j.bbabio.2014.12.006 -
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 Physiology May 2024
Topics: Mitochondria; Plastids; Plants
PubMed: 38590035
DOI: 10.1093/pcp/pcae036