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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 -
Molecular Plant-microbe Interactions :... Mar 2024It has been discovered that plant pathogens produce effectors that spread via plasmodesmata (PD) to allow modulation of host processes in distal uninfected cells. f....
It has been discovered that plant pathogens produce effectors that spread via plasmodesmata (PD) to allow modulation of host processes in distal uninfected cells. f. sp. () facilitates effector translocation by expansion of the size-exclusion limit of PD using the Six5/Avr2 effector pair. How other fungal pathogens manipulate PD is unknown. We recently reported that many fungal pathogens belonging to different families carry effector pairs that resemble the / gene pair from Here, we performed structural predictions of three of these effector pairs from () and tested their ability to manipulate PD and to complement the virulence defect of a knockout mutant. We show that the AvrLm10A homologs are structurally related to FolSix5 and localize at PD when they are expressed with their paired effectors. Furthermore, these effectors were found to complement Six5 function in cell-to-cell mobility assays and in fungal virulence. We conclude that distantly related fungal species rely on structurally related paired effector proteins to manipulate PD and facilitate effector mobility. The wide distribution of these effector pairs implies Six5-mediated effector translocation to be a conserved propensity among fungal plant pathogens. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
Topics: Humans; Fungal Proteins; Virulence; Plasmodesmata; Plant Diseases; Fusarium
PubMed: 37782126
DOI: 10.1094/MPMI-07-23-0103-FI -
Tree Physiology Feb 2024Salt secretion is an important strategy used by the mangrove plant Aegiceras corniculatum to adapt to the coastal intertidal environment. However, the structural,...
Salt secretion is an important strategy used by the mangrove plant Aegiceras corniculatum to adapt to the coastal intertidal environment. However, the structural, developmental and functional analyses on the leaf salt glands, particularly the salt secretion mechanism, are not well documented. In this study, we investigated the structural, developmental and degenerative characteristics and the salt secretion mechanisms of salt glands to further elucidate the mechanisms of salt tolerance of A. corniculatum. The results showed that the salt gland cells have a large number of mitochondria and vesicles, and plenty of plasmodesmata as well, while chloroplasts were found in the collecting cells. The salt glands developed early and began to differentiate at the leaf primordium stage. We observed and defined three stages of salt gland degradation for the first time in A. corniculatum, where the secretory cells gradually twisted and wrinkled inward and collapsed downward as the salt gland degeneration increased and the intensity of salt gland autofluorescence gradually diminished. In addition, we found that the salt secretion rate of the salt glands increased when the treated concentration of NaCl increased, reaching the maximum at 400 mM NaCl. The salt-secreting capacity of the salt glands of the adaxial epidermis is significantly greater than that of the abaxial epidermis. The real-time quantitative PCR results indicate that SAD2, TTG1, GL2 and RBR1 may be involved in regulating the development of the salt glands of A. corniculatum. Moreover, Na+/H+ antiporter, H+-ATPase, K+ channel and Cl- channel may play important roles in the salt secretion of salt glands. In sum mary, this study strengthens the understanding of the structural, developmental and degenerative patterns of salt glands and salt secretion mechanisms in mangrove recretohalophyte A. corniculatum, providing an important reference for further studies at the molecular level.
Topics: Environment; Plant Leaves; Primulaceae; Salt Gland; Sodium Chloride
PubMed: 37769324
DOI: 10.1093/treephys/tpad123 -
Plants (Basel, Switzerland) Sep 2023In the evolution of eukaryotes, the transition from unicellular to simple multicellular organisms has happened multiple times. For the development of complex... (Review)
Review
In the evolution of eukaryotes, the transition from unicellular to simple multicellular organisms has happened multiple times. For the development of complex multicellularity, characterized by sophisticated body plans and division of labor between specialized cells, symplasmic intercellular communication is supposed to be indispensable. We review the diversity of symplasmic connectivity among the eukaryotes and distinguish between distinct types of non-plasmodesmatal connections, plasmodesmata-like structures, and 'canonical' plasmodesmata on the basis of developmental, structural, and functional criteria. Focusing on the occurrence of plasmodesmata (-like) structures in extant taxa of fungi, brown algae (Phaeophyceae), green algae (Chlorophyta), and streptophyte algae, we present a detailed critical update on the available literature which is adapted to the present classification of these taxa and may serve as a tool for future work. From the data, we conclude that, actually, development of complex multicellularity correlates with symplasmic connectivity in many algal taxa, but there might be alternative routes. Furthermore, we deduce a four-step process towards the evolution of canonical plasmodesmata and demonstrate similarity of plasmodesmata in streptophyte algae and land plants with respect to the occurrence of an ER component. Finally, we discuss the urgent need for functional investigations and molecular work on cell connections in algal organisms.
PubMed: 37765506
DOI: 10.3390/plants12183342 -
International Journal of Molecular... Sep 2023To move from cell to cell through plasmodesmata, many plant viruses require the concerted action of two or more movement proteins (MPs) encoded by transport gene modules...
To move from cell to cell through plasmodesmata, many plant viruses require the concerted action of two or more movement proteins (MPs) encoded by transport gene modules of virus genomes. A tetra-cistron movement block (TCMB) is a newly discovered transport module comprising four genes. TCMB encodes three proteins, which are similar to MPs of the transport module known as the "triple gene block", and a protein unrelated to known viral MPs and containing a double-stranded RNA (dsRNA)-binding domain similar to that found in a family of cell proteins, including AtDRB4 and AtHYL1. Here, the latter TCMB protein, named vDRB for virus dsRNA-binding protein, is shown to bind both dsRNA and single-stranded RNA in vitro. In a turnip crinkle virus-based assay, vDRB exhibits the properties of a viral suppressor of RNA silencing (VSR). In the context of potato virus X infection, vDRB significantly decreases the number and size of "dark green islands", regions of local antiviral silencing, supporting the VSR function of vDRB. Nevertheless, vDRB does not exhibit the VSR properties in non-viral transient expression assays. Taken together, the data presented here indicate that vDRB is an RNA-binding protein exhibiting VSR functions in the context of viral infection.
PubMed: 37762447
DOI: 10.3390/ijms241814144 -
Plant Science : An International... Dec 2023Stone cell, a type of lignified cell, is a unique trait in pear and one of the key factors affects pear fruit quality and economic value. The transmissibility of cell...
Stone cell, a type of lignified cell, is a unique trait in pear and one of the key factors affects pear fruit quality and economic value. The transmissibility of cell lignification process has been proven to exist, however the effects of callose on the permeability of plasmodesmata (PD) and how to influence cell lignification processes are still unknown. In this study, the genome-wide analysis of PD callose binding proteins (PDCB) gene family in pear genome was performed, and 25 PbPDCB genes were identified and divided into four branches. Similar intron/exon structural patterns were observed in the same branch, strongly supporting their close evolutionary relationship. The expression of PbPDCB16 was negatively correlated with lignin accumulation through qRT-PCR analysis. With transient expression in pear fruit and stable expression in pear calli, the increased callose content accompanied by decreased lignin content was further observed. Besides, compared with wild type Arabidopsis, the transgenic plants grew slowly, and cell walls in the stem were thinner, while fewer PDs were observed on the cell walls, and the interspore filaments were also blocked in transgenic Arabidopsis through the transmission electron microscope (TEM). In summary, overexpression of PbPDCB16 could promote accumulation of callose at PD to affect the PD-mediated intercellular connectivity, and inhibit the intercellular communication. This study will provide new insight in reducing the lignin content through callose deposition, and also provide the theoretical basis for further exploration of lignin metabolism and cell wall lignification to form stone cells in pear fruit.
Topics: Pyrus; Plasmodesmata; Glucans; Lignin; Fruit; Plant Proteins; Plants, Genetically Modified; Arabidopsis; Gene Expression Regulation, Plant
PubMed: 37748584
DOI: 10.1016/j.plantsci.2023.111876 -
Journal of Plant Research Nov 2023Plants are exposed to a variety of biotic and abiotic stresses, including wounding at the stem. The healing process (tissue reunion) begins immediately after stem...
Plasmodesmata callose binding protein 2 contributes to the regulation of cambium/phloem formation and auxin response during the tissue reunion process in incised Arabidopsis stem.
Plants are exposed to a variety of biotic and abiotic stresses, including wounding at the stem. The healing process (tissue reunion) begins immediately after stem wounding. The plant hormone auxin plays an important role during tissue reunion. In decapitated stems, auxin transport from the shoot apex is reduced and tissue reunion does not occur but is restored by application of indole-3-acetic acid (IAA). In this study, we found that plasmodesmata callose binding protein 2 (PDCB2) affects the expansion of the cambium/phloem region via changes in auxin response during the process of tissue reunion. PDCB2 was expressed in the cortex and endodermis on the incised side of stems 1-3 days after incision. PDCB2-knockout plants showed reduced callose deposition at plasmodesmata and DR5::GUS activity in the endodermis/cortex in the upper region of the incision accompanied by an increase in size of the cambium/phloem region during tissue reunion. In addition, PIN(PIN-FORMED)3, which is involved in lateral auxin transport, was induced by auxin in the cambium/phloem and endodermis/cortex in the upper part of the incision in wild type, but its expression of PIN3 was decreased in pdcb2 mutant. Our results suggest that PDCB2 contributes to the regulation of cambium/phloem development via auxin response.
Topics: Arabidopsis; Phloem; Cambium; Arabidopsis Proteins; Carrier Proteins; Plasmodesmata; Indoleacetic Acids; Gene Expression Regulation, Plant
PubMed: 37707645
DOI: 10.1007/s10265-023-01494-0 -
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 -
Micron (Oxford, England : 1993) Nov 2023Three abiotic stresses, copper application (CS), mechanical rubbing (MS) and water deprivation (WS) applied on miniature rose bushes specifically activate the expression...
Three abiotic stresses, copper application (CS), mechanical rubbing (MS) and water deprivation (WS) applied on miniature rose bushes specifically activate the expression of the CuZn-Superoxide dismutase (SOD). The Cu/Zn-SOD protein immunodetected in the 4th internode was shown engaged in lignification in phloem, cambium and xylem cells. The SOD occurrence was detailed in the vessel associated cells (VACs), using immunogold labeling observed in transmission electron microscopy. The enzyme was detected in mitochondria, plastids, Golgi vesicles, endoplasmic reticulum and plasma membrane. In addition, in pit-fields without plasmodesmata linking vessel associated cells to vessels, the abiotic stresses increased the transfer apparatus volume. The content in unmethylatedpectins increased in wall ingrowths after CS and MS, but not in WS. In addition to the different localization, the SOD was differentially overexpressed according to the applied stress: an isoform detected at 17 kDa under CuSO application, two isoforms respectively detected at 20 and 17 kDa under MS and detected at 17 and 15 kDa under WS. Notably, the only 17 kDa isoform was detected in plasma membrane vesicles from plants submitted to the three stresses. Thus, by increasing the transfer apparatus development, the key role of VACs was emphasized in establishing an adaptative response to abiotic stresses, in miniature rose bushes. Additionally, it has been observed that the differential SOD localization under such stresses sustained the regulatory function of VACs in the transitory sink function of xylem.
Topics: Cell Membrane; Copper; Microscopy, Electron, Transmission; Mitochondria; Superoxide Dismutase-1; Rosa; Stress, Physiological
PubMed: 37657168
DOI: 10.1016/j.micron.2023.103524 -
Plants (Basel, Switzerland) May 2023Somatic embryogenesis (SE) is a process that scientists have been trying to understand for many years because, on the one hand, it is a manifestation of the totipotency... (Review)
Review
Somatic embryogenesis (SE) is a process that scientists have been trying to understand for many years because, on the one hand, it is a manifestation of the totipotency of plant cells, so it enables the study of the mechanisms regulating this process, and, on the other hand, it is an important method of plant propagation. Using SE in basic research and in practice is invaluable. This article describes the latest, but also historical, information on changes in the chemical composition of the cell wall during the transition of cells from the somatic to embryogenic state, and the importance of symplasmic communication during SE. Among wall chemical components, different pectic, AGP, extensin epitopes, and lipid transfer proteins have been discussed as potential apoplastic markers of explant cells during the acquisition of embryogenic competence. The role of symplasmic communication/isolation during SE has also been discussed, paying particular attention to the formation of symplasmic domains within and between cells that carry out different developmental processes. Information about the number and functionality of plasmodesmata (PD) and callose deposition as the main player in symplasmic isolation has also been presented.
PubMed: 37653868
DOI: 10.3390/plants12101951