RESUMO
MAIN CONCLUSION: Developing bryophytes differentially modify their plasmodesmata structure and function. Secondary plasmodesmata formation via twinning appears to be an ancestral trait. Plasmodesmata networks in hornwort sporophyte meristems resemble those of angiosperms. All land-plant taxa use plasmodesmata (PD) cell connections for symplasmic communication. In angiosperm development, PD networks undergo an extensive remodeling by structural and functional PD modifications, and by postcytokinetic formation of additional secondary PD (secPD). Since comparable information on PD dynamics is scarce for the embryophyte sister groups, we investigated maturating tissues of Anthoceros agrestis (hornwort), Physcomitrium patens (moss), and Marchantia polymorpha (liverwort). As in angiosperms, quantitative electron microscopy revealed secPD formation via twinning in gametophytes of all model bryophytes, which gives rise to laterally adjacent PD pairs or to complex branched PD. This finding suggests that PD twinning is an ancient evolutionary mechanism to adjust PD numbers during wall expansion. Moreover, all bryophyte gametophytes modify their existing PD via taxon-specific strategies resembling those of angiosperms. Development of type II-like PD morphotypes with enlarged diameters or formation of pit pairs might be required to maintain PD transport rates during wall thickening. Similar to angiosperm leaves, fluorescence redistribution after photobleaching revealed a considerable reduction of the PD permeability in maturating P. patens phyllids. In contrast to previous reports on monoplex meristems of bryophyte gametophytes with single initials, we observed targeted secPD formation in the multi-initial basal meristems of A. agrestis sporophytes. Their PD networks share typical features of multi-initial angiosperm meristems, which may hint at a putative homologous origin. We also discuss that monoplex and multi-initial meristems may require distinct types of PD networks, with or without secPD formation, to control maintenance of initial identity and positional signaling.
Assuntos
Plasmodesmos , Plasmodesmos/ultraestrutura , Plasmodesmos/metabolismo , Briófitas/crescimento & desenvolvimento , Briófitas/fisiologia , Briófitas/ultraestrutura , Bryopsida/crescimento & desenvolvimento , Bryopsida/fisiologia , Bryopsida/ultraestrutura , Marchantia/genética , Marchantia/crescimento & desenvolvimento , Marchantia/fisiologia , Marchantia/ultraestrutura , Células Germinativas Vegetais/crescimento & desenvolvimento , Anthocerotophyta/fisiologia , Anthocerotophyta/metabolismo , Meristema/crescimento & desenvolvimento , Meristema/ultraestrutura , Meristema/fisiologiaRESUMO
The hyperaccumulation potential of zinc (Zn) and cadmium (Cd) and their synergistic effects were examined in relation to Christmas moss (Vesicularia montagnei (Bél) Broth., Hypnaceae), an aquatic and terrestrial moss, dosed with Cd (Cd1 and Cd2), Zn (Zn1 and Zn2) and combined Zn and Cd (Cd1Zn1 and Cd2Zn2). Zinc promoted plant growth and development, particularly in the highest Zn and combined Zn/Cd treatments (Zn2 and Cd2Zn2). The Zn treatment resulted in substantial moss chlorophyll content and highest percentage relative growth rate in biomass value (0.23 mg L-1 and 106.8%, respectively); however, the Cd2Zn2 treatment achieved maximal production of chlorophyll a and total chlorophyll (0.29 and 0.51 mg L-1, respectively) due to synergistic effects. These findings suggest that Christmas moss is a highly metal-tolerant and adaptable bryophyte species. Zinc was essential for reducing the detrimental effects of Cd while simultaneously promoting moss growth and biomass development. Furthermore, Christmas moss exhibited hyperaccumulation potential for Cd and Zn in the Cd2Zn2 and Zn alone treatments, as evidenced by highest Cd and Zn values in gametophores (1002 and 18,596 mg per colony volume, respectively). Using energy dispersive X-ray fluorescence (EDXRF) spectrometry, atomic percentages of element concentrations in moss gametophores in the Zn2, Cd2 and combined Zn/Cd treatments were generally in the order: K > Ca > P > Zn > Cd. When comparing the atomic percentages of Zn and Cd in gametophores, it is likely that the higher atomic percentage of Zn was because this element is essential for plant growth and development.
Assuntos
Biodegradação Ambiental , Cádmio , Zinco , Zinco/metabolismo , Cádmio/metabolismo , Biodegradação Ambiental/efeitos dos fármacos , Clorofila/metabolismo , Biomassa , Bryopsida/efeitos dos fármacos , Bryopsida/metabolismo , Bryopsida/crescimento & desenvolvimento , Briófitas/crescimento & desenvolvimento , Briófitas/metabolismo , Briófitas/efeitos dos fármacosRESUMO
The CLAVATA pathway plays a key role in the regulation of multicellular shoot and root meristems in flowering plants. In Arabidopsis, CLAVATA 3-like signaling peptides (CLEs) act via receptor-like kinases CLAVATA 1 and CRINKLY 4 (CR4). In the moss Physcomitrium patens, PpCLAVATA and PpCR4 were previously studied independently and shown to play conserved roles in the regulation of cell proliferation and differentiation. The plant calpain DEFECTIVE KERNEL 1 (DEK1) has been identified as another key regulator of cell division and cell fate in vascular plants and bryophytes. The functional interaction between CLAVATA, CR4, and DEK1 remains unknown. Here, we show that P. patens crinkly4 and dek1 mutants respond differently to CLE peptide treatments suggesting their distinct roles in the CLAVATA pathway. Reduced CLAVATA-mediated suppression of leafy shoot growth in Δcr4 mutants indicates that PpCR4 is involved in CLV3p perception, most likely as a receptor. The CLV3p strongly suppressed leaf vein development in Δcr4 mutants, suggesting that other receptors are involved in these processes and indicating a potential role of PpCR4 in organ sensitization to CLEs.
Assuntos
Bryopsida , Proteínas de Plantas , Bryopsida/genética , Bryopsida/crescimento & desenvolvimento , Bryopsida/metabolismo , Proteínas de Plantas/metabolismo , Proteínas de Plantas/genética , Regulação da Expressão Gênica de Plantas , Peptídeos/metabolismo , Células Germinativas Vegetais/crescimento & desenvolvimento , Células Germinativas Vegetais/metabolismoRESUMO
This study investigated the responses of Didymodon constrictus and Hypnum plumaeforme to different light qualities emitted by light-emitting diodes (LEDs), including white light (WL), red light (RL), blue light (BL), yellow light (YL), green light (GL), and a combination of red and blue light (R1B1L). The research analyzed the fluorescence imaging, photosynthetic pigments, coloration, and growth characteristics related to antioxidant enzymes in these two moss species. The results indicated that R1B1L significantly enhanced the content of photosynthetic pigments, maximum relative electron transport rate (rETRmax), saturation light intensity (IK), and the greenness of the moss. RL improved the maximum quantum yield (Fv/Fm), the light energy efficiency of H. plumaeforme and effective quantum yield in both moss species. In contrast, BL notably increased non-photochemical quenching (NPQ), photochemical quenching (qp), and the steady-state fluorescence decrease ratio (RFD) in H. plumaeforme. The application of GL significantly increases the maximum photon yield (Fv/Fm) in D. constrictus, as well as the light energy efficiency and elongation length, resulting in a shift in the color composition of both moss species towards yellow. Among the light treatments, R1B1L had the highest induction rate and promotional effect on the growth of both moss species. These mosses absorbed GL and RL effectively, while BL played a crucial role in the dissipation of heat and electron transfer in H. plumaeforme. This research provides valuable insights for the regulation of LED light environments and the physiological adaptability of moss in artificial cultivation.
Assuntos
Clorofila , Luz , Clorofila/metabolismo , Fluorescência , Briófitas/metabolismo , Briófitas/efeitos da radiação , Briófitas/crescimento & desenvolvimento , Fotossíntese/efeitos da radiação , Fotossíntese/fisiologia , Bryopsida/metabolismo , Bryopsida/efeitos da radiação , Bryopsida/crescimento & desenvolvimentoRESUMO
In eukaryotic cells, organelle and vesicle transport, positioning, and interactions play crucial roles in cytoplasmic organization and function. These processes are governed by intracellular trafficking mechanisms. At the core of that trafficking, the cytoskeleton and directional transport by motor proteins stand out as its key regulators. Plant cell tip growth is a well-studied example of cytoplasm organization by polarization. This polarization, essential for the cell's function, is driven by the cytoskeleton and its associated motors. This review will focus on myosin XI, a molecular motor critical for vesicle trafficking and polarized plant cell growth. We will center our discussion on recent data from the moss Physcomitrium patens and the liverwort Marchantia polymorpha. The biochemical properties and structure of myosin XI in various plant species are discussed, highlighting functional conservation across species. We further explore this conservation of myosin XI function in the process of vesicle transport in tip-growing cells. Existing evidence indicates that myosin XI actively organizes actin filaments in tip-growing cells by a mechanism based on vesicle clustering at their tips. A hypothetical model is presented to explain the essential function of myosin XI in polarized plant cell growth based on vesicle clustering at the tip. The review also provides insight into the in vivo localization and dynamics of myosin XI, emphasizing its role in cytosolic calcium regulation, which influences the polymerization of F-actin. Lastly, we touch upon the need for additional research to elucidate the regulation of myosin function.
Assuntos
Miosinas , Células Vegetais , Miosinas/metabolismo , Células Vegetais/metabolismo , Bryopsida/metabolismo , Bryopsida/crescimento & desenvolvimento , Proteínas de Plantas/metabolismo , Citoesqueleto de Actina/metabolismo , Marchantia/metabolismo , Marchantia/crescimento & desenvolvimento , Desenvolvimento Vegetal/fisiologiaRESUMO
The conquest of land by plants was concomitant with, and possibly enabled by, the evolution of three-dimensional (3D) growth. The moss Physcomitrium patens provides a model system for elucidating molecular mechanisms in the initiation of 3D growth. Here, we investigate whether the phytohormone ethylene, which is believed to have been a signal before land plant emergence, plays a role in 3D growth regulation in P. patens. We report ethylene controls 3D gametophore formation, based on results from exogenously applied ethylene and genetic manipulation of PpEIN2, which is a central component in the ethylene signaling pathway. Overexpression (OE) of PpEIN2 activates ethylene responses and leads to earlier formation of gametophores with fewer gametophores produced thereafter, phenocopying ethylene-treated wild-type. Conversely, Ppein2 knockout mutants, which are ethylene insensitive, show initially delayed gametophore formation with more gametophores produced later. Furthermore, pharmacological and biochemical analyses reveal auxin levels are decreased in the OE lines but increased in the knockout mutants. Our results suggest that evolutionarily, ethylene and auxin molecular networks were recruited to build the plant body plan in ancestral land plants. This might have played a role in enabling ancient plants to acclimate to the continental surfaces of the planet.
Assuntos
Bryopsida , Etilenos , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos , Proteínas de Plantas , Etilenos/metabolismo , Ácidos Indolacéticos/metabolismo , Ácidos Indolacéticos/farmacologia , Bryopsida/crescimento & desenvolvimento , Bryopsida/genética , Bryopsida/efeitos dos fármacos , Bryopsida/metabolismo , Proteínas de Plantas/metabolismo , Proteínas de Plantas/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Células Germinativas Vegetais/metabolismo , Células Germinativas Vegetais/crescimento & desenvolvimento , Células Germinativas Vegetais/efeitos dos fármacos , Mutação/genéticaRESUMO
SUPPRESSOR OF MAX2 (SMAX)1-LIKE (SMXL) proteins are a plant-specific clade of type I HSP100/Clp-ATPases. SMXL genes are present in virtually all land plant genomes. However, they have mainly been studied in angiosperms. In Arabidopsis (Arabidopsis thaliana), 3 functional SMXL subclades have been identified: SMAX1/SMXL2, SMXL345, and SMXL678. Of these, 2 subclades ensure endogenous phytohormone signal transduction. SMAX1/SMXL2 proteins are involved in KAI2 ligand (KL) signaling, while SMXL678 proteins are involved in strigolactone (SL) signaling. Many questions remain regarding the mode of action of these proteins, as well as their ancestral roles. We addressed these questions by investigating the functions of the 4 SMXL genes in the moss Physcomitrium patens. We demonstrate that PpSMXL proteins are involved in the conserved ancestral MAX2-dependent KL signaling pathway and negatively regulate growth. However, PpSMXL proteins expressed in Arabidopsis cannot replace SMAX1 or SMXL2 function in KL signaling, whereas they can functionally replace SMXL4 and SMXL5 and restore root growth. Therefore, the molecular functions of SMXL proteins are conserved, but their interaction networks are not. Moreover, the PpSMXLC/D clade positively regulates SL signal transduction in P. patens. Overall, our data reveal that SMXL proteins in moss mediate crosstalk between the SL and KL signaling pathways.
Assuntos
Proteínas de Arabidopsis , Bryopsida , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas , Bryopsida/genética , Bryopsida/crescimento & desenvolvimento , Bryopsida/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Arabidopsis/genética , Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Transdução de Sinais , Filogenia , Lactonas/metabolismoRESUMO
Bryophytes are nonvascular spore-forming plants. Unlike in flowering plants, the gametophyte (haploid) generation of bryophytes dominates the sporophyte (diploid) generation. A comparison of bryophytes with flowering plants allows us to answer some fundamental questions raised in evolutionary cell and developmental biology. The moss Physcomitrium patens was the first bryophyte with a sequenced genome. Many cell and developmental studies have been conducted in this species using gene targeting by homologous recombination. The liverwort Marchantia polymorpha has recently emerged as an excellent model system with low genomic redundancy in most of its regulatory pathways. With the development of molecular genetic tools such as efficient genome editing, both P. patens and M. polymorpha have provided many valuable insights. Here, we review these advances with a special focus on polarity formation at the cell and tissue levels. We examine current knowledge regarding the cellular mechanisms of polarized cell elongation and cell division, including symmetric and asymmetric cell division. We also examine the role of polar auxin transport in mosses and liverworts. Finally, we discuss the future of evolutionary cell and developmental biological studies in plants.
Assuntos
Evolução Biológica , Bryopsida/fisiologia , Polaridade Celular , Ácidos Indolacéticos/metabolismo , Marchantia/fisiologia , Células Vegetais/fisiologia , Transporte Biológico , Bryopsida/crescimento & desenvolvimento , Biologia Celular , Divisão Celular , Crescimento Celular , Biologia do Desenvolvimento , Marchantia/crescimento & desenvolvimento , Organogênese Vegetal , Reguladores de Crescimento de Plantas/metabolismoRESUMO
Plant viruses are important pathogens able to overcome plant defense mechanisms using their viral suppressors of RNA silencing (VSR). Small RNA pathways of bryophytes and vascular plants have significant similarities, but little is known about how viruses interact with mosses. This study elucidated the responses of Physcomitrella patens to two different VSRs. We transformed P. patens plants to express VSR P19 from tomato bushy stunt virus and VSR 2b from cucumber mosaic virus, respectively. RNA sequencing and quantitative PCR were used to detect the effects of VSRs on gene expression. Small RNA (sRNA) sequencing was used to estimate the influences of VSRs on the sRNA pool of P. patens. Expression of either VSR-encoding gene caused developmental disorders in P. patens. The transcripts of four different transcription factors (AP2/erf, EREB-11 and two MYBs) accumulated in the P19 lines. sRNA sequencing revealed that VSR P19 significantly changed the microRNA pool in P. patens. Our results suggest that VSR P19 is functional in P. patens and affects the abundance of specific microRNAs interfering with gene expression. The results open new opportunities for using Physcomitrella as an alternative system to study plant-virus interactions.
Assuntos
Bryopsida/crescimento & desenvolvimento , Bryopsida/genética , Bryopsida/virologia , Interações Hospedeiro-Patógeno/genética , Cucumovirus/genética , Cucumovirus/patogenicidade , Regulação da Expressão Gênica de Plantas , Regulação Viral da Expressão Gênica , MicroRNAs , Proteínas de Plantas/genética , Vírus de Plantas/genética , Vírus de Plantas/patogenicidade , Plantas Geneticamente Modificadas , Interferência de RNA , Tombusvirus/genética , Tombusvirus/patogenicidade , Fatores de Transcrição/genéticaRESUMO
R-loops, consisting of a DNA:RNA hybrid and a single-stranded DNA (ssDNA), form naturally as functional chromosome structures and are crucial in many vital biological processes. However, disrupted R-loop homeostasis will threat to the integrity and stability of genome. As the endonuclease, RNase H1 can efficiently recognize and remove excess R-loops to protect organisms from DNA damage induced by R-loop over-accumulation. Here, we investigated the function of RNase H1 in Physcomitrium (Physcomitrella) patens to illustrate its important role in the evolution of plants. We found that PpRNH1A dysfunction seriously affected shoot growth and branch formation in P. patens, revealing a noticeable functional difference between PpRNH1A and AtRNH1A of Arabidopsis. Furthermore, auxin signaling was significantly affected at the transcriptional level in PpRNH1A mutant plants, as a result of the accumulation of R-loops at several auxin-related genes. This study provides evidence that PpRNH1A regulates the development of P. patens by controlling R-loop formation at specific loci to modulate the transcription of auxin-related genes. It also highlights the interspecific functional differences between early land plants and vascular plants, despite crucial and conserved role of RNase H1 played in maintaining R-loop homeostasis.
Assuntos
Bryopsida/crescimento & desenvolvimento , Bryopsida/genética , Diferenciação Celular/genética , Ácidos Indolacéticos/metabolismo , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/genética , Ribonuclease H/genética , Diferenciação Celular/fisiologiaRESUMO
In animals, PIEZOs are plasma membrane-localized cation channels involved in diverse mechanosensory processes. We investigated PIEZO function in tip-growing cells in the moss Physcomitrium patens and the flowering plant Arabidopsis thaliana PpPIEZO1 and PpPIEZO2 redundantly contribute to the normal growth, size, and cytoplasmic calcium oscillations of caulonemal cells. Both PpPIEZO1 and PpPIEZO2 localized to vacuolar membranes. Loss-of-function, gain-of-function, and overexpression mutants revealed that moss PIEZO homologs promote increased complexity of vacuolar membranes through tubulation, internalization, and/or fission. Arabidopsis PIEZO1 also localized to the tonoplast and is required for vacuole tubulation in the tips of pollen tubes. We propose that in plant cells the tonoplast has more freedom of movement than the plasma membrane, making it a more effective location for mechanosensory proteins.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Bryopsida/metabolismo , Canais Iônicos/metabolismo , Proteínas de Plantas/metabolismo , Vacúolos/ultraestrutura , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/ultraestrutura , Proteínas de Arabidopsis/genética , Bryopsida/crescimento & desenvolvimento , Bryopsida/ultraestrutura , Cálcio/metabolismo , Sinalização do Cálcio , Citoplasma/metabolismo , Membranas Intracelulares/metabolismo , Canais Iônicos/genética , Proteínas de Plantas/genética , Tubo Polínico/crescimento & desenvolvimento , Tubo Polínico/metabolismo , Tubo Polínico/ultraestrutura , Vacúolos/metabolismoRESUMO
As an adaptive innovation in plant terrestrialization, cuticle covers the plant surface and greatly contributes to the development and stress tolerance in land plants. Although past decades have seen great progress in understanding the molecular mechanism of cuticle biosynthesis in flowering plants with the contribution of cuticle biosynthesis mutants and advanced cuticle composition profiling techniques, origins and evolution of cuticle biosynthesis are poorly understood. Recent chemical, phylogenomic, and molecular genetic studies on cuticle biosynthesis in early-diverging extant land plant lineages, the bryophytes, shed novel light on the origins and evolution of plant cuticle biosynthesis. In this mini-review, we highlighted these recent advances in the molecular biology of cuticle biosynthesis in bryophytes, and provided evolutionary insights into plant cuticle biosynthesis.
Assuntos
Briófitas/crescimento & desenvolvimento , Evolução Molecular , Epiderme Vegetal/crescimento & desenvolvimento , Briófitas/genética , Briófitas/metabolismo , Bryopsida/genética , Bryopsida/crescimento & desenvolvimento , Bryopsida/metabolismo , Epiderme Vegetal/metabolismoRESUMO
As a bryophyte and model plant, the moss Physcomitrium (Physcomitrella) patens (P. patens) is particularly well adapted to hormone evolution studies. Gene targeting through homologous recombination or CRISPR-Cas9 system, genome sequencing, and numerous transcriptomic datasets has allowed for molecular genetics studies and much progress in Evo-Devo knowledge. As to strigolactones, like for other hormones, both phenotypical and transcriptional responses can be studied, in both WT and mutant plants. However, as in any plant species, medium- to large-scale phenotype characterization is necessary, owing to the general high phenotypic variability. Therefore, many biological replicates are required. This may translate to large amount of the investigated compounds, particularly expensive (or difficult to synthesize) in the case of strigolactones. These issues prompted us to improve existing methods to limit the use of scarce/expensive compounds, as well as to simplify subsequent measures/sampling of P. patens. We hence scaled up well-tried experiments, in order to increment the number of tested genotypes in one given experiment.In this chapter, we will describe three methods we set up to study the response to strigolactones and related compounds in P. patens.
Assuntos
Bioensaio , Bryopsida/efeitos dos fármacos , Compostos Heterocíclicos com 3 Anéis/farmacologia , Lactonas/farmacologia , Desenvolvimento Vegetal/efeitos dos fármacos , Reguladores de Crescimento de Plantas/farmacologia , Plantas Geneticamente Modificadas/efeitos dos fármacos , Bryopsida/genética , Bryopsida/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas , Genótipo , Fenótipo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/crescimento & desenvolvimento , Fatores de TempoRESUMO
The moss Physcomitrium (Physcomitrella) patens performs efficient homologous recombination in both the nucleus and plastid enabling the study of individual gene function by generating precise inactivation or modification of genes. Polyethylene glycol (PEG)-mediated transformation of protoplasts is routinely used to study the nuclear gene function of P. patens. PEG-mediated protoplast transformation is also applied for plastid transformation of this moss. The efficiency of plastid transformation is quite reliable and one or two homoplasmic transplastomic lines are obtained in a plastid transformation experiment (5 × 105 protoplasts) by selection for spectinomycin resistance.
Assuntos
Bryopsida/genética , Engenharia Genética/métodos , Plantas Geneticamente Modificadas/genética , Plastídeos/genética , Transformação Genética , Bryopsida/crescimento & desenvolvimento , Recombinação Homóloga , Plantas Geneticamente Modificadas/crescimento & desenvolvimentoRESUMO
Plants have evolved and grown under the selection pressure of gravitational force at 1 g on Earth. In response to this selection pressure, plants have acquired gravitropism to sense gravity and change their growth direction. In addition, plants also adjust their morphogenesis in response to different gravitational forces in a phenomenon known as gravity resistance. However, the gravity resistance phenomenon in plants is poorly understood due to the prevalence of 1 g gravitational force on Earth: not only it is difficult to culture plants at gravity > 1 g(hypergravity) for a long period of time but it is also impossible to create a < 1 genvironment (µg, micro g) on Earth without specialized facilities. Despite these technical challenges, it is important to understand how plants grow in different gravity conditions in order to understand land plant adaptation to the 1 g environment or for outer space exploration. To address this, we have developed a centrifugal device for a prolonged duration of plant culture in hypergravity conditions, and a project to grow plants under the µg environment in the International Space Station is also underway. Our plant material of choice is Physcomitrium (Physcomitrella) patens, one of the pioneer plants on land and a model bryophyte often used in plant biology. In this review, we summarize our latest findings regarding P. patens growth response to hypergravity, with reference to our on-going "Space moss" project. In our ground-based hypergravity experiments, we analyzed the morphological and physiological changes and found unexpected increments of chloroplast size and photosynthesis rate, which might underlie the enhancement of growth and increase in the number of gametophores and rhizoids. We further discussed our approaches at the cellular level and compare the gravity resistance in mosses and that in angiosperms. Finally, we highlight the advantages and perspectives from the space experiments and conclude that research with bryophytes is beneficial to comprehensively and precisely understand gravitational responses in plants.
Assuntos
Bryopsida/crescimento & desenvolvimento , Gravitação , Hipergravidade , Meristema/crescimento & desenvolvimento , Brotos de Planta/crescimento & desenvolvimento , Voo Espacial/métodos , Bryopsida/citologia , Bryopsida/metabolismo , Divisão Celular/fisiologia , Citoesqueleto/metabolismo , Meristema/citologia , Meristema/metabolismo , Modelos Biológicos , Fotossíntese/fisiologia , Brotos de Planta/citologia , Brotos de Planta/metabolismoRESUMO
Plant pathogens often exploit a whole range of effectors to facilitate infection. The RXLR effector AVR1 produced by the oomycete plant pathogen Phytophthora infestans suppresses host defense by targeting Sec5. Sec5 is a subunit of the exocyst, a protein complex that is important for mediating polarized exocytosis during plant development and defense against pathogens. The mechanism by which AVR1 manipulates Sec5 functioning is unknown. In this study, we analyzed the effect of AVR1 on Sec5 localization and functioning in the moss Physcomitrium patens. P. patens has four Sec5 homologs. Two (PpSec5b and PpSec5d) were found to interact with AVR1 in yeast-two-hybrid assays while none of the four showed a positive interaction with AVR1ΔT, a truncated version of AVR1. In P. patens lines carrying ß-estradiol inducible AVR1 or AVR1ΔT transgenes, expression of AVR1 or AVR1ΔT caused defects in the development of caulonemal protonema cells and abnormal morphology of chloronema cells. Similar phenotypes were observed in Sec5- or Sec6-silenced P. patens lines, suggesting that both AVR1 and AVR1ΔT affect exocyst functioning in P. patens. With respect to Sec5 localization we found no differences between ß-estradiol-treated and untreated transgenic AVR1 lines. Sec5 localizes at the plasma membrane in growing caulonema cells, also during pathogen attack, and its subcellular localization is the same, with or without AVR1 in the vicinity.
Assuntos
Bryopsida/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas , Interações Hospedeiro-Patógeno , Phytophthora infestans/patogenicidade , Doenças das Plantas/imunologia , Proteínas de Plantas/metabolismo , Fatores de Virulência/metabolismo , Bryopsida/parasitologia , Doenças das Plantas/parasitologia , Proteínas de Plantas/genética , Fatores de Virulência/genéticaRESUMO
Development in multicellular organisms relies on cell proliferation and specialization. In plants, both these processes critically depend on the spatial organization of cells within a tissue. Owing to an absence of significant cellular migration, the relative position of plant cells is virtually made permanent at the moment of division. Therefore, in numerous plant developmental contexts, the (divergent) developmental trajectories of daughter cells are dependent on division plane positioning in the parental cell. Prior to and throughout division, specific cellular processes inform, establish and execute division plane control. For studying these facets of division plane control, the moss Physcomitrium (Physcomitrella) patens has emerged as a suitable model system. Developmental progression in this organism starts out simple and transitions towards a body plan with a three-dimensional structure. The transition is accompanied by a series of divisions where cell fate transitions and division plane positioning go hand in hand. These divisions are experimentally highly tractable and accessible. In this review, we will highlight recently uncovered mechanisms, including polarity protein complexes and cytoskeletal structures, and transcriptional regulators, that are required for 1D to 3D body plan formation.
Assuntos
Bryopsida , Divisão Celular/fisiologia , Células Vegetais/metabolismo , Desenvolvimento Vegetal/fisiologia , Bryopsida/citologia , Bryopsida/crescimento & desenvolvimentoRESUMO
KEY MESSAGE: This review compares the molecular mechanisms of stem cell control in the shoot apical meristems of mosses and angiosperms and reveals the conserved features and evolution of plant stem cells. The establishment and maintenance of pluripotent stem cells in the shoot apical meristem (SAM) are key developmental processes in land plants including the most basal, bryophytes. Bryophytes, such as Physcomitrium (Physcomitrella) patens and Marchantia polymorpha, are emerging as attractive model species to study the conserved features and evolutionary processes in the mechanisms controlling stem cells. Recent studies using these model bryophyte species have started to uncover the similarities and differences in stem cell regulation between bryophytes and angiosperms. In this review, we summarize findings on stem cell function and its regulation focusing on different aspects including hormonal, genetic, and epigenetic control. Stem cell regulation through auxin, cytokinin, CLAVATA3/EMBRYO SURROUNDING REGION-RELATED (CLE) signaling and chromatin modification by Polycomb Repressive Complex 2 (PRC2) and PRC1 is well conserved. Several transcription factors crucial for SAM regulation in angiosperms are not involved in the regulation of the SAM in mosses, but similarities also exist. These findings provide insights into the evolutionary trajectory of the SAM and the fundamental mechanisms involved in stem cell regulation that are conserved across land plants.
Assuntos
Bryopsida/genética , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Meristema/genética , Brotos de Planta/genética , Células-Tronco/metabolismo , Bryopsida/citologia , Bryopsida/crescimento & desenvolvimento , Divisão Celular/efeitos dos fármacos , Divisão Celular/genética , Ácidos Indolacéticos/farmacologia , Meristema/citologia , Meristema/crescimento & desenvolvimento , Reguladores de Crescimento de Plantas/farmacologia , Proteínas de Plantas/genética , Brotos de Planta/citologia , Brotos de Planta/crescimento & desenvolvimento , Células-Tronco/citologia , Células-Tronco/efeitos dos fármacosRESUMO
KEY MESSAGE: This study focused on the key regulatory function of Physcomitrium patens GRAS12 gene underlying an increasing plant complexity, an important step in plant terrestrialization and the evolutionary history of life. The miR171-GRAS module has been identified as a key player in meristem maintenance in angiosperms. PpGRAS12 is a member of the GRAS family and a validated target for miR171 in Physcomitrium (Physcomitrella) patens. Here we show a regulatory function of miR171 at the gametophytic vegetative growth stage and targeted deletion of the PpGRAS12 gene adversely affects sporophyte production since fewer sporophytes were produced in ΔPpGRAS12 knockout lines compared to wild type moss. Furthermore, highly specific and distinct growth arrests were observed in inducible PpGRAS12 overexpression lines at the protonema stage. Prominent phenotypic aberrations including the formation of multiple apical meristems at the gametophytic vegetative stage in response to elevated PpGRAS12 transcript levels were discovered via scanning electron microscopy. The production of multiple buds in the PpGRAS12 overexpression lines similar to ΔPpCLV1a/1b disruption mutants is accompanied by an upregulation of PpCLE and downregulation of PpCLV1, PpAPB, PpNOG1, PpDEK1, PpRPK2 suggesting that PpGRAS12 acts upstream of these genes and negatively regulates the proposed pathway to specify simplex meristem formation. As CLV signaling pathway components are not present in the chlorophytic or charophytic algae and arose with the earliest land plants, we identified a key regulatory function of PpGRAS12 underlying an increasing plant complexity, an important step in plant terrestrialization and the evolutionary history of life.