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Plant Cell Reports Dec 2023The leaf hyponasty response depends on tip-to-petiole auxin transport. This transport can happen through two parallel pathways: active trans-membrane transport mediated...
The leaf hyponasty response depends on tip-to-petiole auxin transport. This transport can happen through two parallel pathways: active trans-membrane transport mediated by PIN proteins and passive diffusion through plasmodesmata. A plant's ability to counteract potential shading by neighboring plants depends on transport of the hormone auxin. Neighbor sensing at the leaf tip triggers auxin production. Once this auxin reaches the abaxial petiole epidermis, it causes cell elongation, which leads to leaf hyponasty. Two pathways are known to contribute to this intercellular tip-to-petiole auxin movement: (i) transport facilitated by plasma membrane-localized PIN auxin transporters and (ii) diffusion enabled by plasmodesmata. We tested if these two modes of transport are arranged sequentially or in parallel. Moreover, we investigated if they are functionally linked. Mutants in which one of the two pathways is disrupted indicated that both pathways are necessary for a full hyponasty response. Visualization of PIN3-GFP and PIN7-GFP localization indicated PIN-mediated transport in parallel to plasmodesmata-mediated transport along abaxial midrib epidermis cells. We found plasmodesmata-mediated cell coupling in the pin3pin4pin7 mutant to match wild-type levels, indicating no redundancy between pathways. Similarly, PIN3, PIN4 and PIN7 mRNA levels were unaffected in a mutant with disrupted plasmodesmata pathway. Our results provide mechanistic insight on leaf hyponasty, which might facilitate the manipulation of the shade avoidance response in crops.
Topics: Arabidopsis; Plasmodesmata; Biological Transport; Membrane Transport Proteins; Indoleacetic Acids
PubMed: 38117314
DOI: 10.1007/s00299-023-03119-1 -
Plant Physiology and Biochemistry : PPB Jan 2024C photosynthesis in higher plants is carried out by two distinct cell types: mesophyll cells and bundle sheath cells, as a result highly concentrated carbon dioxide is... (Review)
Review
C photosynthesis in higher plants is carried out by two distinct cell types: mesophyll cells and bundle sheath cells, as a result highly concentrated carbon dioxide is released surrounding RuBisCo in chloroplasts of bundle sheath cells and the photosynthetic efficiency is significantly higher than that of C plants. The evolution of the dual-cell C cycle involved complex modifications to leaf anatomy and cell ultra-structures. These include an increase in leaf venation, the formation of Kranz anatomy, changes in chloroplast morphology in bundle sheath cells, and increases in the density of plasmodesmata at interfaces between the bundle sheath and mesophyll cells. It is predicted that cereals will be in severe worldwide shortage at the mid-term of this century. Rice is a staple food that feeds more than half of the world's population. If rice can be engineered to perform C photosynthesis, it is estimated that rice yield will be increased by at least 50% due to enhanced photosynthesis. Thus, the Second Green Revolution has been launched on this principle by genetically installing C photosynthesis into C crops. The studies on molecular mechanisms underlying the changes in leaf morphoanatomy involved in C photosynthesis have made great progress in recent years. As there are plenty of reviews discussing the installment of the C cycle, we focus on the current progress and challenges posed to the research regarding leaf anatomy and cell ultra-structure modifications made towards the development of C rice.
Topics: Oryza; Photosynthesis; Chloroplasts; Plant Leaves; Crops, Agricultural
PubMed: 38091938
DOI: 10.1016/j.plaphy.2023.108256 -
Journal of Experimental Botany Feb 2024This study describes the seasonal changes in cell-to-cell transport in three selected angiosperm tree species, Acer pseudoplatanus (maple), Fraxinus excelsior (ash), and...
This study describes the seasonal changes in cell-to-cell transport in three selected angiosperm tree species, Acer pseudoplatanus (maple), Fraxinus excelsior (ash), and Populus tremula × tremuloides (poplar), with an emphasis on the living wood component, xylem parenchyma cells (XPCs). We performed anatomical studies, dye loading through the vascular system, measurements of non-structural carbohydrate content, immunocytochemistry, inhibitory assays and quantitative real-time PCR to analyse the transport mechanisms and seasonal variations in wood. The abundance of membrane dye in wood varied seasonally along with seasonally changing tree phenology, cambial activity, and non-structural carbohydrate content. Moreover, dyes internalized in vessel-associated cells and 'trapped' in the endomembrane system are transported farther between other XPCs via plasmodesmata. Finally, various transport mechanisms based on clathrin-mediated and clathrin-independent endocytosis, and membrane transporters, operate in wood, and their involvement is species and/or season dependent. Our study highlights the importance of XPCs in seasonally changing cell-to-cell transport in both ring-porous (ash) and diffuse-porous (maple, poplar) tree species, and demonstrates the involvement of both endocytosis and plasmodesmata in intercellular communication in angiosperm wood.
Topics: Wood; Seasons; Magnoliopsida; Xylem; Populus; Clathrin; Carbohydrates
PubMed: 37996075
DOI: 10.1093/jxb/erad469 -
Methods in Molecular Biology (Clifton,... 2024Infection by positive-strand RNA viruses induces extensive remodeling of the host endomembrane system in favor of viral replication and movement. The integral membrane...
Monitoring the Intracellular Trafficking of Virus-Induced Structures and Intercellular Spread of Viral Infection in Plants Using Endomembrane Trafficking Pathway-Specific Chemical Inhibitor and Organelle-Selective Fluorescence Dye.
Infection by positive-strand RNA viruses induces extensive remodeling of the host endomembrane system in favor of viral replication and movement. The integral membrane protein 6K2 of potyviruses induces the formation of membranous virus replication vesicles at the endoplasmic reticulum exit site (ERES). The intracellular trafficking of 6K2-induced vesicles along with microfilaments requires the vesicular transport pathway, actomyosin motility system, and possibly post-Golgi compartments such as endosomes as well. Recent studies have shown that endocytosis is essential for the intracellular movement of potyviruses from the site of viral genome replication/assembly site to plasmodesmata (PD) to enter neighboring cells. In this chapter, we describe a detailed protocol of how to use endomembrane trafficking pathway-specific chemical inhibitors and organelle-selective fluorescence dye to study the trafficking of potyviral proteins and potyvirus-induced vesicles and to unravel the role of endocytosis and the endocytic pathway in potyvirus infection in Nicotiana benthamiana plants.
Topics: Fluorescence; Endoplasmic Reticulum; Golgi Apparatus; Virus Diseases; Nicotiana; Fluorescent Dyes; Potyvirus
PubMed: 37987903
DOI: 10.1007/978-1-0716-3485-1_10 -
Molecular Plant-microbe Interactions :... Feb 2024In plants, plasmodesmata establish cytoplasmic continuity between cells to allow for communication and resource exchange across the cell wall. While plant pathogens use...
In plants, plasmodesmata establish cytoplasmic continuity between cells to allow for communication and resource exchange across the cell wall. While plant pathogens use plasmodesmata as a pathway for both molecular and physical invasion, the benefits of molecular invasion (cell-to-cell movement of pathogen effectors) are poorly understood. To establish a methodology for identification and characterization of the cell-to-cell mobility of effectors, we performed a quantitative live imaging-based screen of candidate effectors of the fungal pathogen . We predicted effectors by their expression profiles, the presence of a secretion signal, and their predicted and in planta localization when fused to green fluorescent protein. We assayed for cell-to-cell mobility of nucleocytosolic effectors and identified 14 that are cell-to-cell mobile. We identified that three of these effectors are "hypermobile," showing cell-to-cell mobility greater than expected for a protein of that size. To explore the mechanism of hypermobility, we chose two hypermobile effectors and measured their impact on plasmodesmata function and found that even though they show no direct association with plasmodesmata, each increases the transport capacity of plasmodesmata. Thus, our methods for quantitative analysis of cell-to-cell mobility of candidate microbe-derived effectors, or any suite of host proteins, can identify cell-to-cell hypermobility and offer greater understanding of how proteins affect plasmodesmal function and intercellular connectivity. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
Topics: Plasmodesmata; Plants; Cytoplasm; Cytosol; Cell Wall
PubMed: 37942798
DOI: 10.1094/MPMI-05-23-0052-TA -
Trends in Plant Science Jan 2024Brassinosteroids (BRs) are exceptional phytohormones: they do not undergo a long-distance transport between plant organs. However, the mechanism of short-distance...
Brassinosteroids (BRs) are exceptional phytohormones: they do not undergo a long-distance transport between plant organs. However, the mechanism of short-distance (intercellular) transport of BRs remains poorly understood. Recently, Wang et al. provided a novel insight into the mutual dependence of BR homeostasis, their intercellular transport, and plasmodesmata permeability.
Topics: Brassinosteroids; Plasmodesmata; Plant Growth Regulators; Plants; Homeostasis; Gene Expression Regulation, Plant
PubMed: 37919125
DOI: 10.1016/j.tplants.2023.10.010 -
The New Phytologist Jan 2024In leaves of C plants, the reactions of photosynthesis become restricted between two compartments. Typically, this allows accumulation of C acids in mesophyll (M) cells...
In leaves of C plants, the reactions of photosynthesis become restricted between two compartments. Typically, this allows accumulation of C acids in mesophyll (M) cells and subsequent decarboxylation in the bundle sheath (BS). In C grasses, proliferation of plasmodesmata between these cell types is thought to increase cell-to-cell connectivity to allow efficient metabolite movement. However, it is not known whether C dicotyledons also show this enhanced plasmodesmal connectivity and so whether this is a general requirement for C photosynthesis is not clear. How M and BS cells in C leaves become highly connected is also not known. We investigated these questions using 3D- and 2D-electron microscopy on the C dicotyledon Gynandropsis gynandra as well as phylogenetically close C relatives. The M-BS interface of C G. gynandra showed higher plasmodesmal frequency compared with closely related C species. Formation of these plasmodesmata was induced by light. Pharmacological agents that perturbed photosynthesis reduced the number of plasmodesmata, but this inhibitory effect could be reversed by the provision of exogenous sucrose. We conclude that enhanced formation of plasmodesmata between M and BS cells is wired to the induction of photosynthesis in C G. gynandra.
Topics: Mesophyll Cells; Plasmodesmata; Plant Leaves; Photosynthesis; Poaceae; Magnoliopsida
PubMed: 37882365
DOI: 10.1111/nph.19343 -
Biology Open Oct 2023Cell-cell communication is a central feature of multicellular organisms, enabling division of labour and coordinated responses. Plasmodesmata are membrane-lined pores... (Review)
Review
Cell-cell communication is a central feature of multicellular organisms, enabling division of labour and coordinated responses. Plasmodesmata are membrane-lined pores that provide regulated cytoplasmic continuity between plant cells, facilitating signalling and transport across neighboring cells. Plant development and survival profoundly depend on the existence and functioning of these structures, bringing them to the spotlight for both fundamental and applied research. Despite the rich conceptual and translational rewards in sight, however, the study of plasmodesmata poses significant challenges. This Review will mostly focus on research published between May 2022 and May 2023 and intends to provide a short overview of recent discoveries, innovations, community resources and hypotheses.
Topics: Plasmodesmata; Cell Communication; Signal Transduction; Plant Development; Biology
PubMed: 37874138
DOI: 10.1242/bio.060123 -
BioRxiv : the Preprint Server For... Oct 2023Callose, a beta-(1,3)-D-glucan polymer, is essential for regulating intercellular trafficking via plasmodesmata (PD). Pathogens manipulate PD-localized proteins to...
Callose, a beta-(1,3)-D-glucan polymer, is essential for regulating intercellular trafficking via plasmodesmata (PD). Pathogens manipulate PD-localized proteins to enable intercellular trafficking by removing callose at PD, or conversely by increasing callose accumulation at PD to limit intercellular trafficking during infection. Plant defense hormones like salicylic acid regulate PD-localized proteins to control PD and intercellular trafficking during innate immune defense responses such as systemic acquired resistance. Measuring callose deposition at PD in plants has therefore emerged as a popular parameter for assessing the intercellular trafficking activity during plant immunity. Despite the popularity of this metric there is no standard for how these measurements should be made. In this study, three commonly used methods for identifying and quantifying PD callose by aniline blue staining were evaluated to determine the most effective in the leaf model. The results reveal that the most reliable method used aniline blue staining and fluorescent microscopy to measure callose deposition in fixed tissue. Manual or semi-automated workflows for image analysis were also compared and found to produce similar results although the semi-automated workflow produced a wider distribution of data points.
PubMed: 37873219
DOI: 10.1101/2023.09.30.560305 -
The New Phytologist Jan 2024Most plant reoviruses are phloem-limited, but the mechanism has remained unknown for more than half a century. Southern rice black-streaked dwarf virus (Fijivirus,...
Most plant reoviruses are phloem-limited, but the mechanism has remained unknown for more than half a century. Southern rice black-streaked dwarf virus (Fijivirus, Reoviridae) causes phloem-derived tumors, where its virions, genomes, and proteins accumulate, and it was used as a model to explore how its host plant limits the virus within its phloem. High-throughput volume electron microscopy revealed that only sieve plate pores and flexible gateways rather than plasmodesmata had a sufficiently large size exclusion limit (SEL) to accommodate virions and potentially serve as pathways of virion movement. The large SEL gateways were enriched within the proliferated sieve element (SE) layers of tumors. The lack of such connections out of the SE-enriched regions of tumors defined a size-dependent physical barrier to high flux transportation of virions. A working model is proposed to demonstrate the mechanism underlying limitation of virus within phloem.
Topics: Volume Electron Microscopy; Phloem; Neoplasms
PubMed: 37858933
DOI: 10.1111/nph.19319