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The protein import motor in chloroplasts plays a pivotal role in their biogenesis and homeostasis by driving the translocation of preproteins into chloroplasts. While the Ycf2-FtsHi complex serves as the import motor in land plants, its evolutionary conservation, specialization, and mechanisms across photosynthetic organisms are largely unexplored. Here, we isolated and determined the cryogenic electron microscopy (cryo-EM) structures of the native Ycf2-FtsHi complex from Chlamydomonas reinhardtii, uncovering a complex composed of up to 19 subunits, including multiple green-algae-specific components. The heterohexameric AAA+ ATPase motor module is tilted, potentially facilitating preprotein handover from the translocon at the inner chloroplast membrane (TIC) complex. Preprotein interacts with Ycf2-FtsHi and enhances its ATPase activity in vitro. Integrating Ycf2-FtsHi and translocon at the outer chloroplast membrane (TOC)-TIC supercomplex structures reveals insights into their physical and functional interplay during preprotein translocation. By comparing these findings with those from land plants, our study establishes a structural foundation for understanding the assembly, function, evolutionary conservation, and diversity of chloroplast protein import motors.
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The evolutionary features and molecular innovations that enabled plants to first colonize land are not well understood. Here, insights are provided through our report of the genome sequence of the unicellular alga Penium margaritaceum, a member of the Zygnematophyceae, the sister lineage to land plants. The genome has a high proportion of repeat sequences that are associated with massive segmental gene duplications, likely facilitating neofunctionalization. Compared with representatives of earlier diverging algal lineages, P. margaritaceum has expanded repertoires of gene families, signaling networks, and adaptive responses that highlight the evolutionary trajectory toward terrestrialization. These encompass a broad range of physiological processes and protective cellular features, such as flavonoid compounds and large families of modifying enzymes involved in cell wall biosynthesis, assembly, and remodeling. Transcriptome profiling further elucidated adaptations, responses, and selective pressures associated with the semi-terrestrial ecosystems of P. margaritaceum, where a simple body plan would be an advantage.
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Desmidiales/genética , Desmidiales/metabolismo , Embriófitas/genética , Evolução Biológica , Parede Celular/genética , Parede Celular/metabolismo , Ecossistema , Evolução Molecular , Filogenia , PlantasRESUMO
The evolution of land flora transformed the terrestrial environment. Land plants evolved from an ancestral charophycean alga from which they inherited developmental, biochemical, and cell biological attributes. Additional biochemical and physiological adaptations to land, and a life cycle with an alternation between multicellular haploid and diploid generations that facilitated efficient dispersal of desiccation tolerant spores, evolved in the ancestral land plant. We analyzed the genome of the liverwort Marchantia polymorpha, a member of a basal land plant lineage. Relative to charophycean algae, land plant genomes are characterized by genes encoding novel biochemical pathways, new phytohormone signaling pathways (notably auxin), expanded repertoires of signaling pathways, and increased diversity in some transcription factor families. Compared with other sequenced land plants, M. polymorpha exhibits low genetic redundancy in most regulatory pathways, with this portion of its genome resembling that predicted for the ancestral land plant. PAPERCLIP.
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Evolução Biológica , Embriófitas/genética , Genoma de Planta , Marchantia/genética , Adaptação Biológica , Embriófitas/fisiologia , Regulação da Expressão Gênica de Plantas , Marchantia/fisiologia , Anotação de Sequência Molecular , Transdução de Sinais , Transcrição GênicaRESUMO
Model organisms are extensively used in research as accessible and convenient systems for studying a particular area or question in biology. Traditionally, only a limited number of organisms have been studied in detail, but modern genomic tools are enabling researchers to extend beyond the set of classical model organisms to include novel species from less-studied phylogenetic groups. This review focuses on model species for an important group of multicellular organisms, the brown algae. The development of genetic and genomic tools for the filamentous brown alga Ectocarpus has led to it emerging as a general model system for this group, but additional models, such as Fucus or Dictyota dichotoma, remain of interest for specific biological questions. In addition, Saccharina japonica has emerged as a model system to directly address applied questions related to algal aquaculture. We discuss the past, present, and future of brown algal model organisms in relation to the opportunities and challenges in brown algal research.
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Phaeophyceae/genética , Animais , Genoma/genética , Humanos , Modelos Biológicos , FilogeniaRESUMO
Euglenids have long been studied due to their unique physiology and versatile metabolism, providing underpinnings for much of our understanding of photosynthesis and biochemistry, and a growing opportunity in biotechnology. Until recently there has been a lack of genetic studies due to their large and complex genomes, but recently new technologies have begun to unveil their genetic capabilities. Whilst much research has focused on the model organism Euglena gracilis, other members of the euglenids have now started to receive due attention. Currently only poor nuclear genome assemblies of E. gracilis and Rhabdomonas costata are available, but there are many more plastid genome sequences and an increasing number of transcriptomes. As more assemblies become available, there are great opportunities to understand the fundamental biology of these organisms and to exploit them for biotechnology.
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In many animals and flowering plants, sex determination occurs in the diploid phase of the life cycle with XX/XY or ZW/ZZ sex chromosomes. However, in early diverging plants and most macroalgae, sex is determined by female (U) or male (V) sex chromosomes in a haploid phase called the gametophyte. Once the U and V chromosomes unite at fertilization to produce a diploid sporophyte, sex determination no longer occurs, raising key questions about the fate of the U and V sex chromosomes in the sporophyte phase. Here, we investigate genetic and molecular interactions of the UV sex chromosomes in both the haploid and diploid phases of the brown alga Ectocarpus. We reveal extensive developmental regulation of sex chromosome genes across its life cycle and implicate the TALE-HD transcription factor OUROBOROS in suppressing sex determination in the diploid phase. Small RNAs may also play a role in the repression of a female sex-linked gene, and transition to the diploid sporophyte coincides with major reconfiguration of histone H3K79me2, suggesting a more intricate role for this histone mark in Ectocarpus development than previously appreciated.
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Estágios do Ciclo de Vida , Phaeophyceae , Animais , Phaeophyceae/genética , Fatores de Transcrição/genética , Cromossomos Sexuais/genética , HaploidiaRESUMO
Brown algae are multicellular photosynthetic organisms that have evolved independently of plants and other algae. Here, we studied the determinism of body axis formation in the kelp Saccharina latissima. Following microdissection of the embryo, we showed that the stalk, an empty cell that retains the embryo on the maternal tissue represses longitudinal cell divisions in the early embryo, thereby reinforcing the establishment of the initial apico-basal axis. In addition, it promotes cell growth and controls cell shape and arrangement in the flat, oblong embryo composed of cells aligned in rows and columns. Although the stalk persists for several weeks until the embryo reaches at least 500 cells, proper embryogenesis requires connection to maternal tissue only during the first 4 days after fertilisation, i.e. before the embryo reaches the 8-cell stage. Transplantation experiments indicated that the maternal signal is not diffused in seawater, but requires contact between the embryo and the maternal tissue. This first global quantitative study of brown algal embryogenesis highlights the role of MUM, an unknown maternal message, in the control of growth axes and tissue patterning in kelp embryos. please edit family name.
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Cyanobacteria and chloroplasts of algae and plants harbor specialized thylakoid membranes that convert sunlight into chemical energy. These membranes house photosystems II and I, the vital protein-pigment complexes that drive oxygenic photosynthesis. In the course of their evolution, thylakoid membranes have diversified in structure. However, the core machinery for photosynthetic electron transport remained largely unchanged, with adaptations occurring primarily in the light-harvesting antenna systems. Whereas thylakoid membranes in cyanobacteria are relatively simple they become more complex in algae and plants. The chloroplasts of vascular plants contain intricate networks of stacked grana and unstacked stroma thylakoids. This review provides an in-depth view of thylakoid membrane architectures in phototrophs, and the determinants that shape their forms, as well as presenting recent insights into the spatial organization of their biogenesis and maintenance. Its overall goal is to define the underlying principles that have guided the evolution of these bioenergetic membranes.
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Cyanobacteria, red algae, and cryptophytes produce two classes of proteins for light-harvesting: water-soluble phycobiliproteins and membrane-intrinsic proteins that bind chlorophylls and carotenoids. In cyanobacteria, red algae, and glaucophytes, phycobilisomes (PBS) are complexes of brightly colored phycobiliproteins and linker (assembly) proteins. To date, six structural classes of phycobilisomes have been described: hemiellipsoidal, block-shaped, hemidiscoidal, bundle-shaped, paddle-shaped, and far-red-light bicylindrical. Two additional antenna complexes containing single types of phycobiliproteins have also been described. Since 2017, structures have been reported for examples of all of these complexes except bundle-shaped phycobilisomes by cryogenic electron microscopy. Phycobilisomes range in size from about 4.6 to 18 MDa and can include â¼900 polypeptides and bind >2000 chromophores. Cyanobacteria additionally produce membrane-associated proteins of the PsbC/CP43 superfamily of Chl a/b/d-binding proteins, including the iron-stress protein IsiA and other paralogous chlorophyll-binding proteins that can form antenna complexes with Photosystem I and/or Photosystem II. Red and cryptophyte algae also produce chlorophyll-binding proteins associated with Photosystem I but which belong to the chlorophyll a/b-binding (CAB) protein superfamily and which are unrelated to the chlorophyll-binding proteins (CBP) of cyanobacteria. This review describes recent progress in structure determination for phycobilisomes and the chlorophyll proteins of cyanobacteria, red algae, and cryptophytan algae.
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River ecosystem function depends on flow regimes that are increasingly modified by changes in climate, land use, water extraction, and flow regulation. Given the wide range of variation in flow regime modifications and autotrophic communities in rivers, it has been challenging to predict which rivers will be more resilient to flow disturbances. To better understand how river productivity is disturbed by and recovers from high-flow disturbance events, we used a continental-scale dataset of daily gross primary production time series from 143 rivers to estimate growth of autotrophic biomass and ecologically relevant flow disturbance thresholds using a modified population model. We compared biomass recovery rates across hydroclimatic gradients and catchment characteristics to evaluate macroscale controls on ecosystem recovery. Estimated biomass accrual (i.e., recovery) was fastest in wider rivers with less regulated flow regimes and more frequent instances of biomass removal during high flows. Although disturbance flow thresholds routinely fell below the estimated bankfull flood (i.e., the 2-y flood), a direct comparison of disturbance flows estimated by our biomass model and a geomorphic model revealed that biomass disturbance thresholds were usually greater than bed disturbance thresholds. We suggest that primary producers in rivers vary widely in their capacity to recover following flow disturbances, and multiple, interacting macroscale factors control productivity recovery rates, although river width had the strongest overall effect. Biomass disturbance flow thresholds varied as a function of geomorphology, highlighting the need for data such as bed slope and grain size to predict how river ecosystems will respond to changing flow regimes.
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Ecossistema , Inundações , Rios , Biomassa , ClimaRESUMO
Land plants are astounding processors of information; due to their sessile nature, they adjust the molecular programs that define their development and physiology in accordance with the environment in which they dwell. Transduction of the external input to the respective internal programs hinges to a large degree on molecular signaling cascades, many of which have deep evolutionary origins in the ancestors of land plants and its closest relatives, streptophyte algae. In this Review, we discuss the evolutionary history of the defining factors of streptophyte signaling cascades, circuitries that not only operate in extant land plants and streptophyte algae, but that also likely operated in their extinct algal ancestors hundreds of millions of years ago. We hope this Review offers a starting point for future studies on the evolutionary mechanisms contributing to the current diversity and complexity of plant signaling pathways, with an emphasis on recognizing potential biases.
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Plantas , Transdução de Sinais , Plantas/metabolismo , Plantas/genética , Evolução Molecular , Proteínas de Plantas/metabolismo , Proteínas de Plantas/genéticaRESUMO
The first mitotic division of the initial cell is a key event in all multicellular organisms and is associated with the establishment of major developmental axes and cell fates. The brown alga Ectocarpus has a haploid-diploid life cycle that involves the development of two multicellular generations: the sporophyte and the gametophyte. Each generation deploys a distinct developmental programme autonomously from an initial cell, the first cell division of which sets up the future body pattern. Here, we show that mutations in the BASELESS (BAS) gene result in multiple cellular defects during the first cell division and subsequent failure to produce basal structures during both generations. BAS encodes a type Bâ³ regulatory subunit of protein phosphatase 2A (PP2A), and transcriptomic analysis identified potential effector genes that may be involved in determining basal cell fate. The bas mutant phenotype is very similar to that observed in distag (dis) mutants, which lack a functional Tubulin-binding co-factor Cd1 (TBCCd1) protein, indicating that TBCCd1 and PP2A are two essential components of the cellular machinery that regulates the first cell division and mediates basal cell fate determination.
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Phaeophyceae , Proteína Fosfatase 2 , Proteína Fosfatase 2/genética , Proteína Fosfatase 2/metabolismo , Mutação/genética , Perfilação da Expressão Gênica , Processamento de Proteína Pós-Traducional , Phaeophyceae/genética , Phaeophyceae/metabolismoRESUMO
Basic helix-loop-helix (bHLH) proteins are one of the largest families of transcription factor (TF) in eukaryotes, and ~30% of all flowering plants' bHLH TFs contain the aspartate kinase, chorismate mutase, and TyrA (ACT)-like domain at variable distances C-terminal from the bHLH. However, the evolutionary history and functional consequences of the bHLH/ACT-like domain association remain unknown. Here, we show that this domain association is unique to the plantae kingdom with green algae (chlorophytes) harboring a small number of bHLH genes with variable frequency of ACT-like domain's presence. bHLH-associated ACT-like domains form a monophyletic group, indicating a common origin. Indeed, phylogenetic analysis results suggest that the association of ACT-like and bHLH domains occurred early in Plantae by recruitment of an ACT-like domain in a common ancestor with widely distributed ACT DOMAIN REPEAT (ACR) genes by an ancestral bHLH gene. We determined the functional significance of this association by showing that Chlamydomonas reinhardtii ACT-like domains mediate homodimer formation and negatively affect DNA binding of the associated bHLH domains. We show that, while ACT-like domains have experienced faster selection than the associated bHLH domain, their rates of evolution are strongly and positively correlated, suggesting that the evolution of the ACT-like domains was constrained by the bHLH domains. This study proposes an evolutionary trajectory for the association of ACT-like and bHLH domains with the experimental characterization of the functional consequence in the regulation of plant-specific processes, highlighting the impacts of functional domain coevolution.
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Fatores de Transcrição Hélice-Alça-Hélice Básicos , Plantas , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Filogenia , Plantas/genética , Fatores de Transcrição/metabolismo , Sequências Hélice-Alça-HéliceRESUMO
In brown algae, the extracellular matrix (ECM) and its constitutive polymers play crucial roles in specialized functions, including algal growth and development. In this review we offer an integrative view of ECM construction in brown algae. We briefly report the chemical composition of its main constituents, and how these are interlinked in a structural model. We examine the ECM assembly at the tissue and cell level, with consideration on its structure in vivo and on the putative subcellular sites for the synthesis of its main constituents. We further discuss the biosynthetic pathways of two major polysaccharides, alginates and sulfated fucans, and the progress made beyond the candidate genes with the biochemical validation of encoded proteins. Key enzymes involved in the elongation of the glycan chains are still unknown and predictions have been made at the gene level. Here, we offer a re-examination of some glycosyltransferases and sulfotransferases from published genomes. Overall, our analysis suggests novel investigations to be performed at both the cellular and biochemical levels. First, to depict the location of polysaccharide structures in tissues. Secondly, to identify putative actors in the ECM synthesis to be functionally studied in the future.
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Phaeophyceae , Phaeophyceae/genética , Phaeophyceae/química , Phaeophyceae/metabolismo , Polissacarídeos/química , Polissacarídeos/metabolismo , Genoma , Matriz Extracelular/metabolismoRESUMO
Extremophiles have always garnered great interest because of their exotic lifestyles and ability to thrive at the physical limits of life. In hot springs environments, the Cyanidiophyceae red algae are the only photosynthetic eukaryotes able to live under extremely low pH (0-5) and relatively high temperature (35ºC to 63ºC). These extremophiles live as biofilms in the springs, inhabit acid soils near the hot springs, and form endolithic populations in the surrounding rocks. Cyanidiophyceae represent a remarkable source of knowledge about the evolution of extremophilic lifestyles and their genomes encode specialized enzymes that have applied uses. Here we review the evolutionary origin, taxonomy, genome biology, industrial applications, and use of Cyanidiophyceae as genetic models. Currently, Cyanidiophyceae comprise a single order (Cyanidiales), three families, four genera, and nine species, including the well-known Cyanidioschyzon merolae and Galdieria sulphuraria. These algae have small, gene-rich genomes that are analogous to those of prokaryotes they live and compete with. There are few spliceosomal introns and evidence exists for horizontal gene transfer as a driver of local adaptation to gain access to external fixed carbon and to extrude toxic metals. Cyanidiophyceae offer a variety of commercial opportunities such as phytoremediation to detoxify contaminated soils or waters and exploitation of their mixotrophic lifestyles to support the efficient production of bioproducts such as phycocyanin and floridosides. In terms of exobiology, Cyanidiophyceae are an ideal model system for understanding the evolutionary effects of foreign gene acquisition and the interactions between different organisms inhabiting the same harsh environment on the early Earth. Finally, we describe ongoing research with C. merolae genetics and summarize the unique insights they offer to the understanding of algal biology and evolution.
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Extremófilos , Rodófitas , Humanos , Eucariotos , Extremófilos/genética , Rodófitas/genética , Genoma , Solo , FilogeniaRESUMO
Ostreobium is a siphonous green alga in the Bryopsidales (Chlorophyta) that burrows into calcium carbonate (CaCO3) substrates. In this habitat, it lives under environmental conditions unusual for an alga (i.e., low light and low oxygen) and it is a major agent of carbonate reef bioerosion. In coral skeletons, Ostreobium can form conspicuous green bands recognizable by the naked eye and it is thought to contribute to the coral's nutritional needs. With coral reefs in global decline, there is a renewed focus on understanding Ostreobium biology and its roles in the coral holobiont. This review summarizes knowledge on Ostreobium's morphological structure, biodiversity and evolution, photosynthesis, mechanism of bioerosion and its role as a member of the coral holobiont. We discuss the resources available to study Ostreobium biology, lay out some of the uncharted territories in Ostreobium biology and offer perspectives for future research.
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Antozoários , Clorófitas , Animais , Recifes de Corais , EcossistemaRESUMO
Brown algae are complex multicellular eukaryotes whose cells possess a cell wall, which is an important structure that regulates cell size and shape. Alginate and fucose-containing sulfated polysaccharides (FCSPs) are two carbohydrate types that have major roles in influencing the mechanical properties of the cell wall (i.e. increasing or decreasing wall stiffness), which in turn regulate cell expansion, division, adhesion, and other processes; however, how brown algal cell wall structure regulates its mechanical properties, and how this relationship influences cellular growth and organismal development, is not well-understood. This chapter is focused on reviewing what we currently know about how the roles of alginates and FCSPs in brown algal developmental processes, as well as how they influence the structural and mechanical properties of cell walls. Additionally, we discuss how brown algal mutants may be leveraged to learn more about the underlying mechanisms that regulate cell wall structure, mechanics, and developmental processes, and finally we propose questions to guide future research with the use of emerging technologies.
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Phaeophyceae , Phaeophyceae/genética , Phaeophyceae/química , Phaeophyceae/metabolismo , Parede Celular/química , Polissacarídeos/análise , Polissacarídeos/química , Polissacarídeos/metabolismo , Proliferação de CélulasRESUMO
The monophyletic group of embryophytes (land plants) stands out among photosynthetic eukaryotes: they are the sole constituents of the macroscopic flora on land. In their entirety, embryophytes account for the majority of the biomass on land and constitute an astounding biodiversity. What allowed for the massive radiation of this particular lineage? One of the defining features of all land plants is the production of an array of specialized metabolites. The compounds that the specialized metabolic pathways of embryophytes produce have diverse functions, ranging from superabundant structural polymers and compounds that ward off abiotic and biotic challenges, to signaling molecules whose abundance is measured at the nanomolar scale. These specialized metabolites govern the growth, development, and physiology of land plants-including their response to the environment. Hence, specialized metabolites define the biology of land plants as we know it. And they were likely a foundation for their success. It is thus intriguing to find that the closest algal relatives of land plants, freshwater organisms from the grade of streptophyte algae, possess homologs for key enzymes of specialized metabolic pathways known from land plants. Indeed, some studies suggest that signature metabolites emerging from these pathways can be found in streptophyte algae. Here we synthesize the current understanding of which routes of the specialized metabolism of embryophytes can be traced to a time before plants had conquered land.
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Evolução Biológica , Embriófitas , Plantas , FilogeniaRESUMO
Regulation of gene expression in eukaryotes is controlled by cis-regulatory modules (CRMs). A major class of CRMs are enhancers which are composed of activating cis-regulatory elements (CREs) responsible for upregulating transcription. To date, most enhancers and activating CREs have been studied in angiosperms; in contrast, our knowledge about these key regulators of gene expression in green algae is limited. In this study, we aimed at characterizing putative activating CREs/CRMs from the histone genes of the unicellular model alga Chlamydomonas reinhardtii. To test the activity of four candidates, reporter constructs consisting of a tetramerized CRE, an established promoter, and a gene for the mCerulean3 fluorescent protein were incorporated into the nuclear genome of C. reinhardtii, and their activity was quantified by flow cytometry. Two tested candidates, Eupstr and Ehist cons, significantly upregulated gene expression and were characterized in detail. Eupstr, which originates from highly expressed genes of C. reinhardtii, is an orientation-independent CRE capable of activating both the RBCS2 and ß2-tubulin promoters. Ehist cons, which is a CRM from histone genes of angiosperms, upregulates the ß2-tubulin promoter in C. reinhardtii over a distance of at least 1.5 kb. The octamer motif present in Ehist cons was identified in C. reinhardtii and the related green algae Chlamydomonas incerta, Chlamydomonas schloesseri, and Edaphochlamys debaryana, demonstrating its high evolutionary conservation. The results of this investigation expand our knowledge about the regulation of gene expression in green algae. Furthermore, the characterized activating CREs/CRMs can be applied as valuable genetic tools.
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Chlamydomonas reinhardtii , Histonas , Regiões Promotoras Genéticas , Chlamydomonas reinhardtii/genética , Chlamydomonas reinhardtii/metabolismo , Histonas/metabolismo , Histonas/genética , Regiões Promotoras Genéticas/genética , Regulação da Expressão Gênica de Plantas , Sequências Reguladoras de Ácido Nucleico/genéticaRESUMO
BACKGROUND: Throughout its nearly four-billion-year history, life has undergone evolutionary transitions in which simpler subunits have become integrated to form a more complex whole. Many of these transitions opened the door to innovations that resulted in increased biodiversity and/or organismal efficiency. The evolution of multicellularity from unicellular forms represents one such transition, one that paved the way for cellular differentiation, including differentiation of male and female gametes. A useful model for studying the evolution of multicellularity and cellular differentiation is the volvocine algae, a clade of freshwater green algae whose members range from unicellular to colonial, from undifferentiated to completely differentiated, and whose gamete types can be isogamous, anisogamous, or oogamous. To better understand how multicellularity, differentiation, and gametes evolved in this group, we used comparative genomics and fossil data to establish a geologically calibrated roadmap of when these innovations occurred. RESULTS: Our ancestral-state reconstructions, show that multicellularity arose independently twice in the volvocine algae. Our chronograms indicate multicellularity evolved during the Carboniferous-Triassic periods in Goniaceae + Volvocaceae, and possibly as early as the Cretaceous in Tetrabaenaceae. Using divergence time estimates we inferred when, and in what order, specific developmental changes occurred that led to differentiated multicellularity and oogamy. We find that in the volvocine algae the temporal sequence of developmental changes leading to differentiated multicellularity is much as proposed by David Kirk, and that multicellularity is correlated with the acquisition of anisogamy and oogamy. Lastly, morphological, molecular, and divergence time data suggest the possibility of cryptic species in Tetrabaenaceae. CONCLUSIONS: Large molecular datasets and robust phylogenetic methods are bringing the evolutionary history of the volvocine algae more sharply into focus. Mounting evidence suggests that extant species in this group are the result of two independent origins of multicellularity and multiple independent origins of cell differentiation. Also, the origin of the Tetrabaenaceae-Goniaceae-Volvocaceae clade may be much older than previously thought. Finally, the possibility of cryptic species in the Tetrabaenaceae provides an exciting opportunity to study the recent divergence of lineages adapted to live in very different thermal environments.