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Cell Dec 2022The TOC and TIC complexes are essential translocons that facilitate the import of the nuclear genome-encoded preproteins across the two envelope membranes of...
The TOC and TIC complexes are essential translocons that facilitate the import of the nuclear genome-encoded preproteins across the two envelope membranes of chloroplast, but their exact molecular identities and assembly remain unclear. Here, we report a cryoelectron microscopy structure of TOC-TIC supercomplex from Chlamydomonas, containing a total of 14 identified components. The preprotein-conducting pore of TOC is a hybrid β-barrel co-assembled by Toc120 and Toc75, while the potential translocation path of TIC is formed by transmembrane helices from Tic20 and YlmG, rather than a classic model of Tic110. A rigid intermembrane space (IMS) scaffold bridges two chloroplast membranes, and a large hydrophilic cleft on the IMS scaffold connects TOC and TIC, forming a pathway for preprotein translocation. Our study provides structural insights into the TOC-TIC supercomplex composition, assembly, and preprotein translocation mechanism, and lays a foundation to interpret the evolutionary conservation and diversity of this fundamental translocon machinery.
Topics: Chloroplasts; Cryoelectron Microscopy; Intracellular Membranes; Protein Transport; Chlamydomonas; Multiprotein Complexes; Algal Proteins
PubMed: 36413996
DOI: 10.1016/j.cell.2022.10.030 -
PLoS Biology Dec 2019Peptide-based intercellular communication is a ubiquitous and ancient process that predates evolution of the nervous system. Cilia are essential signaling centers that...
Peptide-based intercellular communication is a ubiquitous and ancient process that predates evolution of the nervous system. Cilia are essential signaling centers that both receive information from the environment and secrete bioactive extracellular vesicles (ectosomes). However, the nature of these secreted signals and their biological functions remain poorly understood. Here, we report the developmentally regulated release of the peptide amidating enzyme, peptidylglycine α-amidating monooxygenase (PAM), and the presence of peptidergic signaling machinery (including propeptide precursors, subtilisin-like prohormone convertases, amidated products, and receptors) in ciliary ectosomes from the green alga Chlamydomonas. One identified amidated PAM product serves as a chemoattractant for mating-type minus gametes but repels plus gametes. Thus, cilia provide a previously unappreciated route for the secretion of amidated signaling peptides. Our study in Chlamydomonas and the presence of PAM in mammalian cilia suggest that ciliary ectosome-mediated peptidergic signaling dates to the early eukaryotes and plays key roles in metazoan physiology.
Topics: Cell Communication; Cell-Derived Microparticles; Chlamydomonas; Chlorophyta; Cilia; Mixed Function Oxygenases; Multienzyme Complexes; Peptides; Signal Transduction
PubMed: 31809498
DOI: 10.1371/journal.pbio.3000566 -
Philosophical Transactions of the Royal... Feb 2020The generation of ciliary waveforms requires the spatial and temporal regulation of dyneins. This review catalogues many of the asymmetric structures and proteins in the... (Review)
Review
The generation of ciliary waveforms requires the spatial and temporal regulation of dyneins. This review catalogues many of the asymmetric structures and proteins in the cilia of , a unicellular alga with two cilia that are used for motility in liquid medium. These asymmetries, which have been identified through mutant analysis, cryo-EM tomography and proteomics, provide a wealth of information to use for modelling how waveforms are generated and propagated. This article is part of the Theo Murphy meeting issue 'Unity and diversity of cilia in locomotion and transport'.
Topics: Chlamydomonas; Cilia; Electron Microscope Tomography; Proteomics
PubMed: 31884924
DOI: 10.1098/rstb.2019.0153 -
The New Phytologist Aug 2021Lipid droplets (LDs) are ubiquitous and specialized organelles in eukaryotic cells. Consisting of a triacylglycerol core surrounded by a monolayer of membrane lipids,... (Review)
Review
Lipid droplets (LDs) are ubiquitous and specialized organelles in eukaryotic cells. Consisting of a triacylglycerol core surrounded by a monolayer of membrane lipids, LDs are decorated with proteins and have myriad functions, from carbon/energy storage to membrane lipid remodeling and signal transduction. The biogenesis and turnover of LDs are therefore tightly coordinated with cellular metabolic needs in a fluctuating environment. Lipid droplet turnover requires remodeling of the protein coat, lipolysis, autophagy and fatty acid β-oxidation. Several key components of these processes have been identified in Chlamydomonas (Chlamydomonas reinhardtii), including the major lipid droplet protein, a CXC-domain containing regulatory protein, the phosphatidylethanolamine-binding DTH1 (DELAYED IN TAG HYDROLYSIS1), two lipases and two enzymes involved in fatty acid β-oxidation. Here, we review LD turnover and discuss its physiological significance in Chlamydomonas, a major model green microalga in research on algal oil.
Topics: Chlamydomonas; Chlamydomonas reinhardtii; Lipase; Lipid Droplets; Lipid Metabolism; Triglycerides
PubMed: 34028037
DOI: 10.1111/nph.17505 -
Journal of Phycology Apr 2020Snow or glacial algae are found on all continents, and most species are in the Chlamydomonadales (Chlorophyta) and Zygnematales (Streptophyta). Other algal groups... (Review)
Review
Snow or glacial algae are found on all continents, and most species are in the Chlamydomonadales (Chlorophyta) and Zygnematales (Streptophyta). Other algal groups include euglenoids, cryptomonads, chrysophytes, dinoflagellates, and cyanobacteria. They may live under extreme conditions of temperatures near 0°C, high irradiance levels in open exposures, low irradiance levels under tree canopies or deep in snow, acidic pH, low conductivity, and desiccation after snow melt. These primary producers may color snow green, golden-brown, red, pink, orange, or purple-grey, and they are part of communities that include other eukaryotes, bacteria, archaea, viruses, and fungi. They are an important component of the global biosphere and carbon and water cycles. Life cycles in the Chlamydomonas-Chloromonas-Chlainomonas complex include migration of flagellates in liquid water and formation of resistant cysts, many of which were identified previously as other algae. Species differentiation has been updated through the use of metagenomics, lipidomics, high-throughput sequencing (HTS), multi-gene analysis, and ITS. Secondary metabolites (astaxanthin in snow algae and purpurogallin in glacial algae) protect chloroplasts and nuclei from damaging PAR and UV, and ice binding proteins (IBPs) and polyunsaturated fatty acids (PUFAs) reduce cell damage in subfreezing temperatures. Molecular phylogenies reveal that snow algae in the Chlamydomonas-Chloromonas complex have invaded the snow habitat at least twice, and some species are polyphyletic. Snow and glacial algae reduce albedo, accelerate the melt of snowpacks and glaciers, and are used to monitor climate change. Selected strains of these algae have potential for producing food or fuel products.
Topics: Chlamydomonas; Chlorophyceae; Chlorophyta; Ecosystem; Ice Cover
PubMed: 31825096
DOI: 10.1111/jpy.12952 -
Proceedings of the National Academy of... Aug 2022Cilium formation and regeneration requires new protein synthesis, but the underlying cytosolic translational reprogramming remains largely unknown. Using ribosome...
Cilium formation and regeneration requires new protein synthesis, but the underlying cytosolic translational reprogramming remains largely unknown. Using ribosome footprinting, we performed global translatome profiling during cilia regeneration in and uncovered that flagellar genes undergo an early transcriptional activation but late translational repression. This pattern guided our identification of sphingolipid metabolism enzymes, including serine palmitoyltransferase (SPT), as essential regulators for ciliogenesis. Cryo-electron tomography showed that ceramide loss abnormally increased the membrane-axoneme distance and generated bulged cilia. We found that ceramides interact with intraflagellar transport (IFT) particle proteins that IFT motors transport along axoneme microtubules (MTs), suggesting that ceramide-IFT particle-IFT motor-MT interactions connect the ciliary membrane with the axoneme to form rod-shaped cilia. SPT-deficient vertebrate cells were defective in ciliogenesis, and SPT mutations from patients with hereditary sensory neuropathy disrupted cilia, which could be restored by sphingolipid supplementation. These results reveal a conserved role of sphingolipid in cilium formation and link compromised sphingolipid production with ciliopathies.
Topics: Axoneme; Ceramides; Chlamydomonas; Cilia; Flagella; Protein Transport; Regeneration; Sphingolipids
PubMed: 35895683
DOI: 10.1073/pnas.2201096119 -
Molecular Vision 2020Intraflagellar transport (IFT) is an essential process in all organisms that serves to move proteins along flagella or cilia in either direction. IFT is performed by IFT... (Review)
Review
Intraflagellar transport (IFT) is an essential process in all organisms that serves to move proteins along flagella or cilia in either direction. IFT is performed by IFT particles, which are multiprotein complexes organized into two subcomplexes, A and B. The IFT proteins form interactions with each other, with cargo proteins, and with membranes during the transport process. Several IFT proteins are expressed in many parts of the retina, such as the outer plexiform and outer nuclear layers, and function in the transport of photoreceptor proteins between the inner and outer segments. Mutants of IFT protein genes have been characterized in model organisms such as , C. , zebrafish, and the mouse. These mutants have defective ciliogenesis or abnormalities in retinal photoreceptors. Mutations in IFT genes are associated with syndromic and non-syndromic forms of retinal disease in humans, frequently with early onset of disease.
Topics: Animals; Caenorhabditis elegans; Chlamydomonas; Flagella; Mice; Mutation; Photoreceptor Cells, Vertebrate; Protein Transport; Retina; Zebrafish
PubMed: 33088169
DOI: No ID Found -
Cells Sep 2019Microalgae have emerged as a promising platform for production of carbon- and energy- rich molecules, notably starch and oil. Establishing an economically viable algal... (Review)
Review
Microalgae have emerged as a promising platform for production of carbon- and energy- rich molecules, notably starch and oil. Establishing an economically viable algal biotechnology sector requires a holistic understanding of algal photosynthesis, physiology, cell cycle and metabolism. Starch/oil productivity is a combined effect of their cellular content and cell division activities. Cell growth, starch and fatty acid synthesis all require carbon building blocks and a source of energy in the form of ATP and NADPH, but with a different requirement in ATP/NADPH ratio. Thus, several cellular mechanisms have been developed by microalgae to balance ATP and NADPH supply which are essentially produced by photosynthesis. Major energy management mechanisms include ATP production by the chloroplast-based cyclic electron flow and NADPH removal by water-water cycles. Furthermore, energetic coupling between chloroplast and other cellular compartments, mitochondria and peroxisome, is increasingly recognized as an important process involved in the chloroplast redox poise. Emerging literature suggests that alterations of energy management pathways affect not only cell fitness and survival, but also influence biomass content and composition. These emerging discoveries are important steps towards diverting algal photosynthetic energy to useful products for biotechnological applications.
Topics: Adenosine Triphosphate; Carbon; Chlamydomonas; Electron Transport; NADP; Photosynthesis; Starch
PubMed: 31561610
DOI: 10.3390/cells8101154 -
Biomolecules Nov 2020With the increase in biotechnological, environmental, and nutraceutical importance of algae, about 100 whole genomic sequences of algae have been published, and this... (Review)
Review
With the increase in biotechnological, environmental, and nutraceutical importance of algae, about 100 whole genomic sequences of algae have been published, and this figure is expected to double in the coming years. The phenotypic and ecological diversity among algae hints at the range of functional capabilities encoded by algal genomes. In order to explore the biodiversity of algae and fully exploit their commercial potential, understanding their evolutionary, structural, functional, and developmental aspects at genomic level is a pre-requisite. So forth, the algal genomic analysis revealed us that algae evolved through endosymbiotic gene transfer, giving rise to around eight phyla. Amongst the diverse algal species, the unicellular green algae has attained the status of model organism as it is an ideal organism to elucidate the biological processes critical to plants and animals, as well as commercialized to produce range of bio-products. For this review, an overview of evolutionary process of algae through endosymbiosis in the light of genomics, as well as the phylogenomic, studies supporting the evolutionary process of algae was reviewed. Algal genomics not only helped us to understand the evolutionary history of algae but also may have an impact on our future by helping to create algae-based products and future biotechnological approaches.
Topics: Chlamydomonas reinhardtii; Evolution, Molecular; Genomics
PubMed: 33172219
DOI: 10.3390/biom10111524 -
The Plant Journal : For Cell and... May 2015The position of Chlamydomonas within the eukaryotic phylogeny makes it a unique model in at least two important ways: as a representative of the critically important,... (Review)
Review
The position of Chlamydomonas within the eukaryotic phylogeny makes it a unique model in at least two important ways: as a representative of the critically important, early-diverging lineage leading to plants; and as a microbe retaining important features of the last eukaryotic common ancestor (LECA) that has been lost in the highly studied yeast lineages. Its cell biology has been studied for many decades and it has well-developed experimental genetic tools, both classical (Mendelian) and molecular. Unlike land plants, it is a haploid with very few gene duplicates, making it ideal for loss-of-function genetic studies. The Chlamydomonas cell cycle has a striking temporal and functional separation between cell growth and rapid cell division, probably connected to the interplay between diurnal cycles that drive photosynthetic cell growth and the cell division cycle; it also exhibits a highly choreographed interaction between the cell cycle and its centriole-basal body-flagellar cycle. Here, we review the current status of studies of the Chlamydomonas cell cycle. We begin with an overview of cell-cycle control in the well-studied yeast and animal systems, which has yielded a canonical, well-supported model. We discuss briefly what is known about similarities and differences in plant cell-cycle control, compared with this model. We next review the cytology and cell biology of the multiple-fission cell cycle of Chlamydomonas. Lastly, we review recent genetic approaches and insights into Chlamydomonas cell-cycle regulation that have been enabled by a new generation of genomics-based tools.
Topics: Animals; Cell Cycle; Chlamydomonas; Cytokinesis; Gene Expression Regulation; Mutation; Phylogeny; Plants; Viridiplantae
PubMed: 25690512
DOI: 10.1111/tpj.12795