RESUMO
Hydroxyproline-rich glycoproteins (HRGPs) are a ubiquitous class of protein in the extracellular matrices and cell walls of plants and algae, yet little is known of their native structures or interactions. Here, we used electron cryomicroscopy (cryo-EM) to determine the structure of the hydroxyproline-rich mastigoneme, an extracellular filament isolated from the cilia of the alga Chlamydomonas reinhardtii. The structure demonstrates that mastigonemes are formed from two HRGPs (a filament of MST1 wrapped around a single copy of MST3) that both have hyperglycosylated poly(hydroxyproline) helices. Within the helices, O-linked glycosylation of the hydroxyproline residues and O-galactosylation of interspersed serine residues create a carbohydrate casing. Analysis of the associated glycans reveals how the pattern of hydroxyproline repetition determines the type and extent of glycosylation. MST3 possesses a PKD2-like transmembrane domain that forms a heteromeric polycystin-like cation channel with PKD2 and SIP, explaining how mastigonemes are tethered to ciliary membranes.
Assuntos
Chlamydomonas reinhardtii , Cílios , Glicoproteínas , Cílios/química , Glicoproteínas/química , Glicosilação , Hidroxiprolina/química , Plantas/metabolismo , Chlamydomonas reinhardtii/químicaRESUMO
Plant cells share a number of biological condensates with cells from other eukaryotes. There are, however, a growing number of plant-specific condensates that support different cellular functions. Condensates operating in different plant tissues contribute to aspects of development and stress responses. To view this SnapShot, open or download the PDF.
Assuntos
Condensados Biomoleculares , Células Vegetais , Plantas , Condensados Biomoleculares/metabolismo , Condensados Biomoleculares/química , Células Vegetais/química , Células Vegetais/metabolismo , Fenômenos Fisiológicos Vegetais , Plantas/química , Plantas/metabolismoRESUMO
The plant-signaling molecule auxin triggers fast and slow cellular responses across land plants and algae. The nuclear auxin pathway mediates gene expression and controls growth and development in land plants, but this pathway is absent from algal sister groups. Several components of rapid responses have been identified in Arabidopsis, but it is unknown if these are part of a conserved mechanism. We recently identified a fast, proteome-wide phosphorylation response to auxin. Here, we show that this response occurs across 5 land plant and algal species and converges on a core group of shared targets. We found conserved rapid physiological responses to auxin in the same species and identified rapidly accelerated fibrosarcoma (RAF)-like protein kinases as central mediators of auxin-triggered phosphorylation across species. Genetic analysis connects this kinase to both auxin-triggered protein phosphorylation and rapid cellular response, thus identifying an ancient mechanism for fast auxin responses in the green lineage.
Assuntos
Embriófitas , Transdução de Sinais , Arabidopsis/genética , Arabidopsis/metabolismo , Embriófitas/metabolismo , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos/metabolismo , Fosforilação , Plantas/metabolismo , Proteínas Quinases/metabolismo , Proteínas de Plantas/metabolismo , Proteínas de Algas/metabolismoRESUMO
Pathogens produce diverse effector proteins to manipulate host cellular processes. However, how functional diversity is generated in an effector repertoire is poorly understood. Many effectors in the devastating plant pathogen Phytophthora contain tandem repeats of the "(L)WY" motif, which are structurally conserved but variable in sequences. Here, we discovered a functional module formed by a specific (L)WY-LWY combination in multiple Phytophthora effectors, which efficiently recruits the serine/threonine protein phosphatase 2A (PP2A) core enzyme in plant hosts. Crystal structure of an effector-PP2A complex shows that the (L)WY-LWY module enables hijacking of the host PP2A core enzyme to form functional holoenzymes. While sharing the PP2A-interacting module at the amino terminus, these effectors possess divergent C-terminal LWY units and regulate distinct sets of phosphoproteins in the host. Our results highlight the appropriation of an essential host phosphatase through molecular mimicry by pathogens and diversification promoted by protein modularity in an effector repertoire.
Assuntos
Monoéster Fosfórico Hidrolases , Phytophthora , Monoéster Fosfórico Hidrolases/metabolismo , Proteínas/metabolismo , Phytophthora/química , Phytophthora/metabolismo , Plantas/metabolismo , Processamento de Proteína Pós-Traducional , Proteína Fosfatase 2/metabolismo , Doenças das PlantasRESUMO
Plant immune receptors often contain TIR domains, which can oligomerize to form active enzyme complexes in response to pathogen infections. In this issue of Cell, Yu and colleagues discover that some plant TIR domains possess a novel 2',3'-cAMP/cGMP synthetase activity that cleaves double-stranded RNA/DNA, triggering cell death during plant immune responses.
Assuntos
Imunidade Vegetal , Receptores Imunológicos , Morte Celular/genética , Imunidade Vegetal/genética , Plantas/metabolismo , Receptores Imunológicos/metabolismoRESUMO
The extracellular pH is a vital regulator of various biological processes in plants. However, how plants perceive extracellular pH remains obscure. Here, we report that plant cell-surface peptide-receptor complexes can function as extracellular pH sensors. We found that pattern-triggered immunity (PTI) dramatically alkalinizes the acidic extracellular pH in root apical meristem (RAM) region, which is essential for root meristem growth factor 1 (RGF1)-mediated RAM growth. The extracellular alkalinization progressively inhibits the acidic-dependent interaction between RGF1 and its receptors (RGFRs) through the pH sensor sulfotyrosine. Conversely, extracellular alkalinization promotes the alkaline-dependent binding of plant elicitor peptides (Peps) to its receptors (PEPRs) through the pH sensor Glu/Asp, thereby promoting immunity. A domain swap between RGFR and PEPR switches the pH dependency of RAM growth. Thus, our results reveal a mechanism of extracellular pH sensing by plant peptide-receptor complexes and provide insights into the extracellular pH-mediated regulation of growth and immunity in the RAM.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Concentração de Íons de Hidrogênio , Meristema/metabolismo , Peptídeos/metabolismo , Células Vegetais , Raízes de Plantas/metabolismo , Plantas/metabolismo , Receptores de Superfície Celular/metabolismo , Transdução de SinaisRESUMO
Plant cells build nanofibrillar walls that are central to plant growth, morphogenesis and mechanics. Starting from simple sugars, three groups of polysaccharides, namely, cellulose, hemicelluloses and pectins, with very different physical properties are assembled by the cell to make a strong yet extensible wall. This Review describes the physics of wall growth and its regulation by cellular processes such as cellulose production by cellulose synthase, modulation of wall pH by plasma membrane H+-ATPase, wall loosening by expansin and signalling by plant hormones such as auxin and brassinosteroid. In addition, this Review discusses the nuanced roles, properties and interactions of cellulose, matrix polysaccharides and cell wall proteins and describes how wall stress and wall loosening cooperatively result in cell wall growth.
Assuntos
Parede Celular , Celulose , Células Vegetais , Parede Celular/metabolismo , Celulose/metabolismo , Células Vegetais/metabolismo , Proteínas de Plantas/metabolismo , Desenvolvimento Vegetal/fisiologia , Plantas/metabolismo , Polissacarídeos/metabolismo , Glucosiltransferases/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Transdução de SinaisRESUMO
The anaphase-promoting complex/cyclosome (APC/C) represents a large multisubunit E3-ubiquitin ligase complex that controls the unidirectional progression through the cell cycle by the ubiquitination of specific target proteins, marking them for proteasomal destruction. Although the APC/C's role is largely conserved among eukaryotes, its subunit composition and target spectrum appear to be species specific. In this review, we focus on the plant APC/C complex, whose activity correlates with different developmental processes, including polyploidization and gametogenesis. After an introduction into proteolytic control by ubiquitination, we discuss the composition of the plant APC/C and the essential nature of its core subunits for plant development. Subsequently, we describe the APC/C activator subunits and interactors, most being plant specific. Finally, we provide a comprehensive list of confirmed and suspected plant APC/C target proteins. Identification of growth-related targets might offer opportunities to increase crop yield and resilience of plants to climate change by manipulating APC/C activity.
Assuntos
Anáfase , Plantas , Ciclossomo-Complexo Promotor de Anáfase/genética , Ciclossomo-Complexo Promotor de Anáfase/metabolismo , Ciclo Celular , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Plantas/genética , Plantas/metabolismo , Ubiquitinação , Ubiquitinas/metabolismoRESUMO
Plants are foundational for global ecological and economic systems, but most plant proteins remain uncharacterized. Protein interaction networks often suggest protein functions and open new avenues to characterize genes and proteins. We therefore systematically determined protein complexes from 13 plant species of scientific and agricultural importance, greatly expanding the known repertoire of stable protein complexes in plants. By using co-fractionation mass spectrometry, we recovered known complexes, confirmed complexes predicted to occur in plants, and identified previously unknown interactions conserved over 1.1 billion years of green plant evolution. Several novel complexes are involved in vernalization and pathogen defense, traits critical for agriculture. We also observed plant analogs of animal complexes with distinct molecular assemblies, including a megadalton-scale tRNA multi-synthetase complex. The resulting map offers a cross-species view of conserved, stable protein assemblies shared across plant cells and provides a mechanistic, biochemical framework for interpreting plant genetics and mutant phenotypes.
Assuntos
Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Mapas de Interação de Proteínas/fisiologia , Espectrometria de Massas/métodos , Plantas/genética , Plantas/metabolismo , Mapeamento de Interação de Proteínas/métodos , Proteômica/métodosRESUMO
Calcium (Ca2+) is a unique mineral that serves as both a nutrient and a signal in all eukaryotes. To maintain Ca2+ homeostasis for both nutrition and signaling purposes, the tool kit for Ca2+ transport has expanded across kingdoms of eukaryotes to encode specific Ca2+ signals referred to as Ca2+ signatures. In parallel, a large array of Ca2+-binding proteins has evolved as specific sensors to decode Ca2+ signatures. By comparing these coding and decoding mechanisms in fungi, animals, and plants, both unified and divergent themes have emerged, and the underlying complexity will challenge researchers for years to come. Considering the scale and breadth of the subject, instead of a literature survey, in this review we focus on a conceptual framework that aims to introduce readers to the principles and mechanisms of Ca2+ signaling. We finish with several examples of Ca2+-signaling pathways, including polarized cell growth, immunity and symbiosis, and systemic signaling, to piece together specific coding and decoding mechanisms in plants versus animals.
Assuntos
Sinalização do Cálcio , Cálcio , Animais , Cálcio/metabolismo , Homeostase , Plantas/genética , Plantas/metabolismoRESUMO
Nutrients are vital to life through intertwined sensing, signaling, and metabolic processes. Emerging research focuses on how distinct nutrient signaling networks integrate and coordinate gene expression, metabolism, growth, and survival. We review the multifaceted roles of sugars, nitrate, and phosphate as essential plant nutrients in controlling complex molecular and cellular mechanisms of dynamic signaling networks. Key advances in central sugar and energy signaling mechanisms mediated by the evolutionarily conserved master regulators HEXOKINASE1 (HXK1), TARGET OF RAPAMYCIN (TOR), and SNF1-RELATED PROTEIN KINASE1 (SNRK1) are discussed. Significant progress in primary nitrate sensing, calcium signaling, transcriptome analysis, and root-shoot communication to shape plant biomass and architecture are elaborated. Discoveries on intracellular and extracellular phosphate signaling and the intimate connections with nitrate and sugar signaling are examined. This review highlights the dynamic nutrient, energy, growth, and stress signaling networks that orchestrate systemwide transcriptional, translational, and metabolic reprogramming, modulate growth and developmental programs, and respond to environmental cues.
Assuntos
Desenvolvimento Vegetal , Transdução de Sinais , Nutrientes , Desenvolvimento Vegetal/genética , Plantas/genética , Plantas/metabolismo , Transdução de Sinais/genéticaRESUMO
Reactive oxygen species (ROS) are key signalling molecules that enable cells to rapidly respond to different stimuli. In plants, ROS play a crucial role in abiotic and biotic stress sensing, integration of different environmental signals and activation of stress-response networks, thus contributing to the establishment of defence mechanisms and plant resilience. Recent advances in the study of ROS signalling in plants include the identification of ROS receptors and key regulatory hubs that connect ROS signalling with other important stress-response signal transduction pathways and hormones, as well as new roles for ROS in organelle-to-organelle and cell-to-cell signalling. Our understanding of how ROS are regulated in cells by balancing production, scavenging and transport has also increased. In this Review, we discuss these promising developments and how they might be used to increase plant resilience to environmental stress.
Assuntos
Plantas , Estresse Fisiológico , Hormônios/metabolismo , Plantas/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Transdução de SinaisRESUMO
Since the discovery of eukaryotic small RNAs as the main effectors of RNA interference in the late 1990s, diverse types of endogenous small RNAs have been characterized, most notably microRNAs, small interfering RNAs (siRNAs) and PIWI-interacting RNAs (piRNAs). These small RNAs associate with Argonaute proteins and, through sequence-specific gene regulation, affect almost every major biological process. Intriguing features of small RNAs, such as their mechanisms of amplification, rapid evolution and non-cell-autonomous function, bestow upon them the capacity to function as agents of intercellular communications in development, reproduction and immunity, and even in transgenerational inheritance. Although there are many types of extracellular small RNAs, and despite decades of research, the capacity of these molecules to transmit signals between cells and between organisms is still highly controversial. In this Review, we discuss evidence from different plants and animals that small RNAs can act in a non-cell-autonomous manner and even exchange information between species. We also discuss mechanistic insights into small RNA communications, such as the nature of the mobile agents, small RNA signal amplification during transit, signal perception and small RNA activity at the destination.
Assuntos
Proteínas Argonautas , MicroRNAs , RNA Interferente Pequeno , Animais , Proteínas Argonautas/genética , Proteínas Argonautas/metabolismo , MicroRNAs/genética , MicroRNAs/metabolismo , Plantas/genética , Plantas/metabolismo , Interferência de RNA , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismoRESUMO
Plants constantly perceive internal and external cues, many of which they need to address to safeguard their proper development and survival. They respond to these cues by selective activation of specific metabolic pathways involving a plethora of molecular players that act and interact in complex networks. In this review, we illustrate and discuss the complexity in the combinatorial control of plant specialized metabolism. We hereby go beyond the intuitive concept of combinatorial control as exerted by modular-acting complexes of transcription factors that govern expression of specialized metabolism genes. To extend this discussion, we also consider all known hierarchical levels of regulation of plant specialized metabolism and their interfaces by referring to reported regulatory concepts from the plant field. Finally, we speculate on possible yet-to-be-discovered regulatory principles of plant specialized metabolism that are inspired by knowledge from other kingdoms of life and areas of biological research.
Assuntos
Plantas/metabolismo , Evolução Biológica , Cromatina/metabolismo , Regulação da Expressão Gênica de Plantas , Família Multigênica , Plantas/genética , Transdução de SinaisRESUMO
Plants greatly rely on their root microbiome for uptake of nutrients and protection against stresses. Recent studies have uncovered the involvement of plant stress responses in the assembly of plant-beneficial microbiomes. To facilitate durable crop production, deciphering the driving forces that shape the microbiome is crucial.
Assuntos
Interações entre Hospedeiro e Microrganismos , Microbiota/fisiologia , Raízes de Plantas/microbiologia , Microbiologia do Solo , Modelos Biológicos , Raízes de Plantas/metabolismo , Plantas/metabolismo , Plantas/microbiologia , Rizosfera , Solo/químicaRESUMO
O-glycosylation is one of the most abundant and diverse types of post-translational modifications of proteins. O-glycans modulate the structure, stability, and function of proteins and serve generalized as well as highly specific roles in most biological processes. This ShapShot presents types of O-glycans found in different organisms and their principle biosynthetic pathways. To view this SnapShot, open or download the PDF.
Assuntos
Evolução Molecular , Processamento de Proteína Pós-Traducional , Animais , Bactérias/genética , Bactérias/metabolismo , Drosophila/genética , Drosophila/metabolismo , Fungos/genética , Fungos/metabolismo , Glicosilação , Nematoides/genética , Nematoides/metabolismo , Plantas/metabolismo , Vertebrados/genética , Vertebrados/metabolismoRESUMO
Abscisic acid is a key phytohormone produced in response to abiotic stress conditions and is an activator of abiotic stress resistance mechanisms and a regulator during diverse developmental stages in plants. This SnapShot explores how ABA signaling operates and coordinates resistance during stress responses and modulates plant development.
Assuntos
Ácido Abscísico/metabolismo , Desenvolvimento Vegetal , Transdução de Sinais , Reguladores de Crescimento de Plantas/metabolismo , Plantas/metabolismoRESUMO
Ice-binding proteins (IBPs) are a diverse class of proteins that assist organism survival in the presence of ice in cold climates. They have different origins in many organisms, including bacteria, fungi, algae, diatoms, plants, insects, and fish. This review covers the gamut of IBP structures and functions and the common features they use to bind ice. We discuss mechanisms by which IBPs adsorb to ice and interfere with its growth, evidence for their irreversible association with ice, and methods for enhancing the activity of IBPs. The applications of IBPs in the food industry, in cryopreservation, and in other technologies are vast, and we chart out some possibilities.
Assuntos
Adaptação Fisiológica/genética , Proteínas Anticongelantes/química , Criopreservação/métodos , Gelo/análise , Animais , Proteínas Anticongelantes/genética , Proteínas Anticongelantes/metabolismo , Bactérias/genética , Bactérias/metabolismo , Temperatura Baixa , Armazenamento de Alimentos/métodos , Expressão Gênica , Humanos , Modelos Moleculares , Plantas/genética , Plantas/metabolismo , Ligação Proteica , Domínios Proteicos , Engenharia de Proteínas , Estrutura Secundária de Proteína , Leveduras/genética , Leveduras/metabolismoRESUMO
Plants are equipped with the capacity to respond to a large number of diverse signals, both internal ones and those emanating from the environment, that are critical to their survival and adaption as sessile organisms. These signals need to be integrated through highly structured intracellular networks to ensure coherent cellular responses, and in addition, spatiotemporal actions of hormones and peptides both orchestrate local cell differentiation and coordinate growth and physiology over long distances. Further, signal interactions and signaling outputs vary significantly with developmental context. This review discusses our current understanding of the integrated intracellular and intercellular signaling networks that control plant growth.
Assuntos
Desenvolvimento Vegetal , Plantas/metabolismo , Meio Ambiente , Luz , Células Vegetais/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismoRESUMO
Soluble sugars serve five main purposes in multicellular organisms: as sources of carbon skeletons, osmolytes, signals, and transient energy storage and as transport molecules. Most sugars are derived from photosynthetic organisms, particularly plants. In multicellular organisms, some cells specialize in providing sugars to other cells (e.g., intestinal and liver cells in animals, photosynthetic cells in plants), whereas others depend completely on an external supply (e.g., brain cells, roots and seeds). This cellular exchange of sugars requires transport proteins to mediate uptake or release from cells or subcellular compartments. Thus, not surprisingly, sugar transport is critical for plants, animals, and humans. At present, three classes of eukaryotic sugar transporters have been characterized, namely the glucose transporters (GLUTs), sodium-glucose symporters (SGLTs), and SWEETs. This review presents the history and state of the art of sugar transporter research, covering genetics, biochemistry, and physiology-from their identification and characterization to their structure, function, and physiology. In humans, understanding sugar transport has therapeutic importance (e.g., addressing diabetes or limiting access of cancer cells to sugars), and in plants, these transporters are critical for crop yield and pathogen susceptibility.