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Current Opinion in Plant Biology Jun 2018Current conceptions of sucrose export largely neglect the effect of transpiration-induced water potential gradients within leaf mesophyll, even as the mix of convection... (Review)
Review
Current conceptions of sucrose export largely neglect the effect of transpiration-induced water potential gradients within leaf mesophyll, even as the mix of convection and diffusion in the pre-phloem path remains uncertain. It is also generally held that the relative importance of convection and diffusion in the pre-phloem path is controlled by the ratio of their respective mass transfer coefficients. Here, we consider pre-phloem sucrose transport in the presence of adverse water potential gradients, finding that whether convection impedes or aids sucrose delivery to the phloem is independent of the permeability of the plasmodesmata to bulk flow, and depends only on assimilation rate, path-length, and the diffusivity. For most tissues subject to transpiration, convection through plasmodesmata pushes sugar away from the phloem.
Topics: Biological Transport; Diffusion; Plant Leaves; Plants; Plasmodesmata; Sucrose; Water
PubMed: 29704829
DOI: 10.1016/j.pbi.2018.04.007 -
Annual Review of Plant Biology 2012Plant cells are surrounded by cellulosic cell walls, creating a potential challenge to resource sharing and information exchange between individual cells. To overcome... (Review)
Review
Plant cells are surrounded by cellulosic cell walls, creating a potential challenge to resource sharing and information exchange between individual cells. To overcome this, plants have evolved channels called plasmodesmata that provide cytoplasmic continuity between each cell and its immediate neighbors. We first review plasmodesmata basics-their architecture, their origin, the types of cargo they transport, and their molecular components. The bulk of this review discusses the regulation of plasmodesmata formation and function. Historically, plasmodesmata research has focused intensely on uncovering regulatory or structural proteins that reside within or immediately adjacent to plasmodesmata. Recent findings, however, underscore that plasmodesmata are exquisitely sensitive to signals far removed from the plasmodesmal channel itself. Signals originating from molecules and pathways that regulate cellular homeostasis-such as reactive oxygen species, organelle-organelle signaling, and organelle-nucleus signaling-lead to astonishing alterations in gene expression that affect plasmodesmata formation and function.
Topics: Arabidopsis; Biological Transport; Cell Communication; Cell Wall; Chloroplasts; Cytoplasm; Glucans; Plant Cells; Plant Development; Plant Proteins; Plasmodesmata; Reactive Oxygen Species; Signal Transduction; Ultrasonography
PubMed: 22136566
DOI: 10.1146/annurev-arplant-042811-105453 -
Current Opinion in Plant Biology Dec 2021Fruit consumption is fundamental to a balanced diet. The contemporary challenge of maintaining a steady food supply to meet the demands of a growing population is... (Review)
Review
Fruit consumption is fundamental to a balanced diet. The contemporary challenge of maintaining a steady food supply to meet the demands of a growing population is driving the development of strategies to improve the production and nutritional quality of fruit. Plasmodesmata, the structures that mediate symplasmic transport between plant cells, play an important role in phloem unloading and distribution of sugars and signalling molecules into developing organs. Targeted modifications to the structures and functioning of plasmodesmata have the potential to improve fruit development; however, knowledge on the mechanisms underpinning plasmodesmata regulation in this context is scarce. In this review, we have compiled current knowledge on plasmodesmata and their structural characterisation during the development of fruit organs. We discuss key questions on phloem unloading, including the pathway shift from symplasmic to apoplastic that takes place during the onset of ripening as potential targets for improving fruit quality.
Topics: Biological Transport; Fruit; Phloem; Plasmodesmata; Sugars
PubMed: 34826657
DOI: 10.1016/j.pbi.2021.102145 -
American Journal of Botany Sep 2021
Topics: Hormones; Indoleacetic Acids; Plant Development; Plant Growth Regulators; Plasmodesmata
PubMed: 34580857
DOI: 10.1002/ajb2.1733 -
The Plant Cell Apr 2015
Topics: Arabidopsis; Arabidopsis Proteins; Membrane Lipids; Plasmodesmata
PubMed: 25818625
DOI: 10.1105/tpc.15.00218 -
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 -
Physiologia Plantarum Jul 2003In the gravity-perceiving cells (statocytes), located in the centre of the root cap, polarity is expressed in the arrangement of the organelles since, in most genera,... (Review)
Review
In the gravity-perceiving cells (statocytes), located in the centre of the root cap, polarity is expressed in the arrangement of the organelles since, in most genera, the nucleus and the endoplasmic reticulum are maintained at the opposite ends of each cell by actin. Polarity is also evident in the distribution of plasmodesmata, which are more numerous in the transverse walls than in the longitudinal walls. The centre of each statocyte is depleted of microtubules (they are only located at the periphery) but is occupied by numerous amyloplasts (statoliths), denser than the cytoplasm. The amyloplasts do not contribute to the inherent structural polarity since their position is dependent upon the gravity vector. This article focuses on new microscopic analyses and on data obtained from experiments performed in microgravity, which have contributed to our better understanding of the architecture of the actin web implicated in the perception of gravity. Depending upon the plant, the actin network seems to be formed of single filaments arranged in various ways, or, of thin bundles of actin filaments. The amyloplasts are enmeshed in this web of actin and their envelopes are associated with it, but they can have autonomous movement via myosin in the absence of gravity. From calculations of the value of the force necessary to move one amyloplast in the lentil root, and from videomicroscopy performed with living statocytes of maize roots, it is hypothesized that actin microfilaments could be orientated in an overall diagonal direction in the statocyte. These observations could help in understanding how slight amyloplast movements may trigger and transmit the gravitropic signal.
Topics: Actin Cytoskeleton; Cell Polarity; Endoplasmic Reticulum; Extracellular Matrix; Gravity Sensing; Plant Root Cap; Plasmodesmata; Plastids; Space Flight; Weightlessness
PubMed: 14631938
DOI: 10.1034/j.1399-3054.2003.00121.x -
The New Phytologist Feb 2015
Topics: Cell Communication; Plant Cells; Plants; Plasmodesmata
PubMed: 25580654
DOI: 10.1111/nph.13254 -
Molecular Plant-microbe Interactions :... Nov 2010As channels that provide cell-to-cell connectivity, plasmodesmata are central to the local and systemic spread of viruses in plants. This review discusses the current... (Review)
Review
As channels that provide cell-to-cell connectivity, plasmodesmata are central to the local and systemic spread of viruses in plants. This review discusses the current state of knowledge of the structure and function of these channels and the ways in which viruses bring about functional changes that allow macromolecular trafficking to occur. Despite the passing of two decades since the first identification of a viral movement protein that mediates these changes, our understanding of the relevant molecular mechanisms remains in its infancy. However, viral movement proteins provide valuable tools for the modification of plasmodesmata and will continue to assist in the dissection of plasmodesmal properties in relation to their core roles in cell-to-cell communication.
Topics: Biological Transport; Plant Diseases; Plant Viral Movement Proteins; Plant Viruses; Plants; Plasmodesmata
PubMed: 20687788
DOI: 10.1094/MPMI-05-10-0116 -
Annual Review of Plant Biology May 2022Sucrose is transported from sources (mature leaves) to sinks (importing tissues such as roots, stems, fruits, and seeds) through the phloem tissues in veins. In many... (Review)
Review
Sucrose is transported from sources (mature leaves) to sinks (importing tissues such as roots, stems, fruits, and seeds) through the phloem tissues in veins. In many herbaceous crop species, sucrose must first be effluxed to the cell wall by a sugar transporter of the SWEET family prior to being taken up into phloem companion cells or sieve elements by a different sugar transporter, called SUT or SUC. The import of sucrose into these cells is termed apoplasmic phloem loading. In sinks, sucrose can similarly exit the phloem apoplasmically or, alternatively, symplasmically through plasmodesmata into connecting parenchyma storage cells. Recent advances describing the regulation and manipulation of sugar transporter expression and activities provide stimulating new insights into sucrose phloem loading in sources and unloading processes in sink tissues. Additionally, new breakthroughs have revealed distinct subpopulations of cells in leaves with different functions pertaining to phloem loading. These and other discoveries in sucrose transport are discussed.
Topics: Biological Transport; Phloem; Plant Leaves; Plant Proteins; Plasmodesmata; Sucrose
PubMed: 35171647
DOI: 10.1146/annurev-arplant-070721-083240