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Journal of Plant Research Jan 2015Plasmodesmata (PD) are intercellular connections in plants which play roles in various developmental processes. They are also found in brown algae, a group of eukaryotes... (Review)
Review
Plasmodesmata (PD) are intercellular connections in plants which play roles in various developmental processes. They are also found in brown algae, a group of eukaryotes possessing complex multicellularity, as well as green plants. Recently, we conducted an ultrastructural study of PD in several species of brown algae. PD in brown algae are commonly straight plasma membrane-lined channels with a diameter of 10-20 nm and they lack desmotubule in contrast to green plants. Moreover, branched PD could not be observed in brown algae. In the brown alga, Dictyota dichotoma, PD are produced during cytokinesis through the formation of their precursor structures (pre-plasmodesmata, PPD). Clustering of PD in a structure termed "pit field" was recognized in several species having a complex multicellular thallus structure but not in those having uniseriate filamentous or multiseriate one. The pit fields might control cell-to-cell communication and contribute to the establishment of the complex multicellular thallus. In this review, we discuss fundamental morphological aspects of brown algal PD and present questions that remain open.
Topics: Cell Wall; Cytokinesis; Phaeophyceae; Plasmodesmata
PubMed: 25516500
DOI: 10.1007/s10265-014-0677-4 -
Current Opinion in Plant Biology Feb 2020Plasmodesmata pores control the entry and exit of molecules at cell-to-cell boundaries. Hundreds of pores perforate the plant cell wall, connecting cells together and... (Review)
Review
Plasmodesmata pores control the entry and exit of molecules at cell-to-cell boundaries. Hundreds of pores perforate the plant cell wall, connecting cells together and establishing direct cytosolic and membrane continuity. This ability to connect cells in such a way is a hallmark of plant physiology and is thought to have allowed sessile multicellularity in Plantae kingdom. Indeed, plasmodesmata-mediated cell-to-cell signalling is fundamental to many plant-related processes. In fact, there are so many facets of plant biology under the control of plasmodesmata that it is hard to conceive how such tiny structures can do so much. While they provide 'open doors' between cells, they also need to guarantee cellular identities and territories by selectively transporting molecules. Although plasmodesmata operating mode remains difficult to grasp, little by little plant scientists are divulging their secrets. In this review, we highlight novel functions of cell-to-cell signalling and share recent insights into how plasmodesmata structural and molecular signatures confer functional specificity and plasticity to these unique cellular machines.
Topics: Cell Communication; Cell Membrane; Cell Wall; Plant Physiological Phenomena; Plasmodesmata
PubMed: 31805513
DOI: 10.1016/j.pbi.2019.10.009 -
International Journal of Molecular... Feb 2021Plants are constantly exposed to a wide range of potential pathogens and to protect themselves, have developed a variety of chemical and physical defense mechanisms.... (Review)
Review
Plants are constantly exposed to a wide range of potential pathogens and to protect themselves, have developed a variety of chemical and physical defense mechanisms. Callose is a β-(1,3)-D-glucan that is widely distributed in higher plants. In addition to its role in normal growth and development, callose plays an important role in plant defense. Callose is deposited between the plasma membrane and the cell wall at the site of pathogen attack, at the plasmodesmata, and on other plant tissues to slow pathogen invasion and spread. Since it was first reported more than a century ago, defense-related callose deposition has been extensively studied in a wide-spectrum of plant-pathogen systems. Over the past 20 years or so, a large number of studies have been published that address the dynamic nature of pathogen-induced callose deposition, the complex regulation of synthesis and transport of defense-related callose and associated callose synthases, and its important roles in plant defense responses. In this review, we summarize our current understanding of the regulation and function of defense-related callose deposition in plants and discuss both the progresses and future challenges in addressing this complex defense mechanism as a critical component of a plant immune system.
Topics: Gene Expression Regulation, Plant; Glucans; Glucosyltransferases; Host-Pathogen Interactions; Plant Physiological Phenomena; Plant Proteins
PubMed: 33673633
DOI: 10.3390/ijms22052393 -
Molecular Plant Jan 2016Intercellular and supracellular communications through plasmodesmata are involved in vital processes for plant development and physiological responses. Micro- and... (Review)
Review
Intercellular and supracellular communications through plasmodesmata are involved in vital processes for plant development and physiological responses. Micro- and macromolecules, including hormones, RNA, and proteins, serve as biological information vectors that traffic through the plasmodesmata between cells. Previous studies demonstrated that the plasmodesmata are elaborately regulated, whereby a long queue of multiple signaling molecules forms. However, the mechanism by which these signals are coupled or coordinated in terms of simultaneous transport in a single channel remains a puzzle. In the last few years, several phytohormones that could function as both non-cell-autonomous signals and plasmodesmal regulators have been disclosed. Plasmodesmal regulators such as auxin, salicylic acid, reactive oxygen species, gibberellic acids, chitin, and jasmonic acid could regulate intercellular trafficking by adjusting plasmodesmal permeability. Here, callose, along with β-glucan synthase and β-glucanase, plays a critical role in regulating plasmodesmal permeability. Interestingly, most of the previously identified regulators are capable of diffusing through the plasmodesmata. Given the small sizes of these molecules, the plasmodesmata are prominent intercellular channels that allow diffusion-based movement of those signaling molecules. Obviously, intercellular communication is under the control of a major mechanism, named a feedback loop, at the plasmodesmata, which mediates complicated biological behaviors. Prospective research on the mechanism of coupling micromolecules at the plasmodesmata for developmental signaling and nutrient provision will help us to understand how plants coordinate their development and photosynthetic assimilation, which is important for agriculture.
Topics: Cell Communication; Glucans; Glucosyltransferases; Plant Growth Regulators; Plants; Plasmodesmata; Signal Transduction
PubMed: 26384246
DOI: 10.1016/j.molp.2015.08.015 -
Protoplasma Jan 2011The turnover of callose (β-1,3-glucan) within cell walls is an essential process affecting many developmental, physiological and stress related processes in plants. The... (Review)
Review
The turnover of callose (β-1,3-glucan) within cell walls is an essential process affecting many developmental, physiological and stress related processes in plants. The deposition and degradation of callose at the neck region of plasmodesmata (Pd) is one of the cellular control mechanisms regulating Pd permeability during both abiotic and biotic stresses. Callose accumulation at Pd is controlled by callose synthases (CalS; EC 2.4.1.34), endogenous enzymes mediating callose synthesis, and by β-1,3-glucanases (BG; EC 3.2.1.39), hydrolytic enzymes which specifically degrade callose. Transcriptional and posttranslational regulation of some CalSs and BGs are strongly controlled by stress signaling, such as that resulting from pathogen invasion. We review the role of Pd-associated callose in the regulation of intercellular communication during developmental, physiological, and stress response processes. Special emphasis is placed on the involvement of Pd-callose in viral pathogenicity. Callose accumulation at Pd restricts virus movement in both compatible and incompatible interactions, while its degradation promotes pathogen spread. Hence, studies on mechanisms of callose turnover at Pd during viral cell-to-cell spread are of importance for our understanding of host mechanisms exploited by viruses in order to successfully spread within the infected plant.
Topics: Arabidopsis; Gene Expression Regulation; Glucan 1,3-beta-Glucosidase; Glucans; Glucosyltransferases; Permeability; Plant Development; Plant Physiological Phenomena; Plant Viruses; Plants; Plasmodesmata; Stress, Physiological
PubMed: 21116665
DOI: 10.1007/s00709-010-0247-0 -
Frontiers in Plant Science 2012Cell-to-cell communication is fundamental to multicellular life. For this to occur effectively there must be pathways and dynamic networks for communication. These might...
Cell-to-cell communication is fundamental to multicellular life. For this to occur effectively there must be pathways and dynamic networks for communication. These might depend upon electrical or chemical signals or the mass transfer of molecules between adjacent cells. Molecular communication occurs either via an extra-cellular pathway or through physical structures, called plasmodesmata, that connect the cytoplasm of neighboring cells. Plasmodesmata bridge the rigid physical barrier presented by the cell wall to extend the symplasm from single cells to tissue domains that have functional importance for tissue growth, development, and defense. Although recent years have seen advances in our knowledge of the physical nature of PD, the trafficked molecules, and of the wider processes they affect, our knowledge of PD structure and function is still relatively rudimentary. This article will consider the technical/experimental difficulties hindering PD research and suggest priorities in the future research effort that might advance the field at a significantly faster rate.
PubMed: 22645579
DOI: 10.3389/fpls.2012.00030 -
Molecular Plant-microbe Interactions :... Jan 2020Plasmodesmata (PD) are essential for intercellular trafficking of molecules required for plant life, from small molecules like sugars and ions to macromolecules... (Review)
Review
Plasmodesmata (PD) are essential for intercellular trafficking of molecules required for plant life, from small molecules like sugars and ions to macromolecules including proteins and RNA molecules that act as signals to regulate plant development and defense. As obligate intracellular pathogens, plant viruses have evolved to manipulate this communication system to facilitate the initial cell-to-cell and eventual systemic spread in their plant hosts. There has been considerable interest in how viruses manipulate the PD that connect the protoplasts of neighboring cells, and viruses have yielded invaluable tools for probing the structure and function of PD. With recent advances in biochemistry and imaging, we have gained new insights into the composition and structure of PD in the presence and absence of viruses. Here, we first discuss viral strategies for manipulating PD for their intercellular movement and examine how this has shed light on our understanding of native PD function. We then address the controversial role of the cytoskeleton in trafficking to and through PD. Finally, we address how viruses could alter PD structure and consider possible mechanisms of the phenomenon described as 'gating'. This discussion supports the significance of virus research in elucidating the properties of PD, these persistently enigmatic plant organelles.
Topics: Cytoskeleton; Plant Development; Plant Viruses; Plants; Plasmodesmata; Protein Transport; Signal Transduction
PubMed: 31715107
DOI: 10.1094/MPMI-07-19-0212-FI -
Plant, Cell & Environment Feb 2023Cell walls are essential for plant growth and development, providing support and protection from external environments. Callose is a glucan that accumulates in... (Review)
Review
Cell walls are essential for plant growth and development, providing support and protection from external environments. Callose is a glucan that accumulates in specialized cell wall microdomains including around intercellular pores called plasmodesmata. Despite representing a small percentage of the cell wall (~0.3% in the model plant Arabidopsis thaliana), callose accumulation regulates important biological processes such as phloem and pollen development, cell division, organ formation, responses to pathogenic invasion and to changes in nutrients and toxic metals in the soil. Callose accumulation modifies cell wall properties and restricts plasmodesmata aperture, affecting the transport of signaling proteins and RNA molecules that regulate plant developmental and environmental responses. Although the importance of callose, at and outside plasmodesmata cell walls, is widely recognized, the underlying mechanisms controlling changes in its synthesis and degradation are still unresolved. In this review, we explore the most recent literature addressing callose metabolism with a focus on the molecular factors affecting callose accumulation in response to mutualistic symbionts and pathogenic elicitors. We discuss commonalities in the signaling pathways, identify research gaps and highlight opportunities to target callose in the improvement of plant responses to beneficial versus pathogenic microbes.
Topics: Plasmodesmata; Plants; Arabidopsis; Glucans; Cell Wall
PubMed: 36478232
DOI: 10.1111/pce.14510 -
Plants (Basel, Switzerland) Aug 2023In order to adapt to sessile life and terrestrial environments, vascular plants have developed highly sophisticated cells to transport photosynthetic products and... (Review)
Review
In order to adapt to sessile life and terrestrial environments, vascular plants have developed highly sophisticated cells to transport photosynthetic products and developmental signals. Of these, two distinct cell types (i.e., the sieve element (SE) and companion cell) are arranged in precise positions, thus ensuring effective transport. During SE differentiation, most of the cellular components are heavily modified or even eliminated. This peculiar differentiation implies the selective disintegration of the nucleus (i.e., enucleation) and the loss of cellular translational capacity. However, some cellular components necessary for transport (e.g., plasmalemma) are retained and specific phloem proteins (P-proteins) appear. Likewise, MYB (i.e., ) and NAC (i.e., and ) transcription factors (TFs) and OCTOPUS proteins play a notable role in SE differentiation. The maturing SEs become heavily dependent on neighboring non-conducting companion cells, to which they are connected by plasmodesmata through which only 20-70 kDa compounds seem to be able to pass. The study of sieve tube proteins still has many gaps. However, the development of a protocol to isolate proteins that are free from any contaminating proteins has constituted an important advance. This review considers the very detailed current state of knowledge of both bound and soluble sap proteins, as well as the role played by the companion cells in their presence. Phloem proteins travel long distances by combining two modes: non-selective transport via bulk flow and selective regulated movement. One of the goals of this study is to discover how the protein content of the sieve tube is controlled. The majority of questions and approaches about the heterogeneity of phloem sap will be clarified once the morphology and physiology of the plasmodesmata have been investigated in depth. Finally, the retention of specific proteins inside an SE is an aspect that should not be forgotten.
PubMed: 37687278
DOI: 10.3390/plants12173033 -
Journal of Experimental Botany Dec 2017The intercellular transport of molecules through membranous channels that traverse the cell walls-so-called plasmodesmata-is of fundamental importance for plant... (Review)
Review
The intercellular transport of molecules through membranous channels that traverse the cell walls-so-called plasmodesmata-is of fundamental importance for plant development. Regulation of plasmodesmata aperture (and transport capacity) is mediated by changes in the flanking cell walls, mainly via the synthesis/degradation (turnover) of the (1,3)-β-glucan polymer callose. The role of callose in organ development and in plant environmental responses is well recognized, but detailed understanding of the mechanisms regulating its accumulation and its effects on the structure and permeability of the channels is still missing. We compiled information on the molecular components and signalling pathways involved in callose turnover at plasmodesmata and, more generally, on the structural and mechanical properties of (1,3)-β-glucan polymers in cell walls. Based on this revision, we propose models integrating callose, cell walls, and the regulation of plasmodesmata structure and intercellular communication. We also highlight new tools and interdisciplinary approaches that can be applied to gain further insight into the effects of modifying callose in cell walls and its consequences for intercellular signalling.
Topics: Biological Transport; Cell Wall; Glucans; Models, Biological; Plant Physiological Phenomena; Plasmodesmata; Signal Transduction
PubMed: 29040641
DOI: 10.1093/jxb/erx337