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Plant, Cell & Environment Jan 2024Reactive oxygen species (ROS) are important signalling molecules that influence many aspects of plant biology. One way in which ROS influence plant growth and...
Reactive oxygen species (ROS) are important signalling molecules that influence many aspects of plant biology. One way in which ROS influence plant growth and development is by modifying intercellular trafficking through plasmodesmata (PD). Viruses have evolved to use PD for their local cell-to-cell spread between plant cells, so it is therefore not surprising that they have found ways to modulate ROS and redox signalling to optimise PD function for their benefit. This review examines how intracellular signalling via ROS and redox pathways regulate intercellular trafficking via PD during development and stress. The relationship between viruses and ROS-redox systems, and the strategies viruses employ to control PD function by interfering with ROS-redox in plants is also discussed.
PubMed: 38168864
DOI: 10.1111/pce.14805 -
Protoplasma Jan 2024In this study, the results of the first detection of callose within the ovules of the representatives of the family Crassulaceae are presented. This study was carried...
In this study, the results of the first detection of callose within the ovules of the representatives of the family Crassulaceae are presented. This study was carried out on three species of the genus Sedum. Data analysis showed differences in the callose deposition pattern between Sedum hispanicum and Sedum ser. Rupestria species during megasporogenesis. Callose was present mostly in the transversal walls of dyads and tetrads in S. hispanicum. Furthermore, a complete loss of callose from the cell walls of the linear tetrad and a gradual and simultaneous deposition of callose within the nucellus of S. hispanicum were observed. The findings of this study showed the presence of hypostase with callose in the ovules of S. hispanicum, which is not common in other angiosperms. The remaining species tested in this study-Sedum sediforme and Sedum rupestre-showed a typical, well-known callose deposition pattern for plants with the monospore type of megasporogenesis and the Polygonum type of embryo sac. The functional megaspore (FM) in all studied species was located most chalazally. FM is a mononuclear cell, which wall is callose-free in the chalazal pole. The study presents the causes of different patterns of callose deposition within Sedum and their relationship with the systematic position of the study species. Moreover, embryological studies present an argument for excluding callose as a substance that forms an electron-dense material near the plasmodesmata in megaspores of S. hispanicum. This research expands the knowledge about the embryological processes of succulent plants from the family Crassulaceae.
Topics: Sedum; Crassulaceae; Gametogenesis, Plant; Plasmodesmata; Glucans
PubMed: 37418158
DOI: 10.1007/s00709-023-01879-x -
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 -
Plant Physiology May 2024Cassava (Manihot esculenta) is a deciduous woody perennial shrub that stores large amounts of carbon and water in its storage roots. Previous studies have shown that...
Cassava (Manihot esculenta) is a deciduous woody perennial shrub that stores large amounts of carbon and water in its storage roots. Previous studies have shown that assimilate unloading into storage roots happens symplasmically once secondary anatomy is established. However, mechanisms controlling phloem loading and overall carbon partitioning to different cassava tissues remain unclear. Here, we used a combination of histological, transcriptional, and biochemical analyses on different cassava tissues and at different timepoints to better understand source-sink carbon allocation. We found that cassava likely utilizes a predominantly passive symplasmic phloem loading strategy, indicated by the lack of expression of genes coding for key players of sucrose transport, the existence of branched plasmodesmata in the companion cell/bundle sheath interface of minor leaf veins, and very high leaf sucrose concentrations. Furthermore, we showed that tissue-specific changes in anatomy and non-structural carbohydrate (NSC) contents are associated with tissue-specific modification in gene expression for sucrose cleavage/synthesis, as well as subcellular compartmentalization of sugars. Overall, our data suggest that carbon allocation during storage root filling is mostly facilitated symplasmically and is likely mostly regulated by local tissue demand and subcellular compartmentalization.
PubMed: 38775728
DOI: 10.1093/plphys/kiae298 -
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 -
PLoS Pathogens Mar 2024Plant viruses must move through plasmodesmata (PD) to complete their life cycles. For viruses in the Potyviridae family (potyvirids), three viral factors (P3N-PIPO, CI,...
Plant viruses must move through plasmodesmata (PD) to complete their life cycles. For viruses in the Potyviridae family (potyvirids), three viral factors (P3N-PIPO, CI, and CP) and few host proteins are known to participate in this event. Nevertheless, not all the proteins engaging in the cell-to-cell movement of potyvirids have been discovered. Here, we found that HCPro2 encoded by areca palm necrotic ring spot virus (ANRSV) assists viral intercellular movement, which could be functionally complemented by its counterpart HCPro from a potyvirus. Affinity purification and mass spectrometry identified several viral factors (including CI and CP) and host proteins that are physically associated with HCPro2. We demonstrated that HCPro2 interacts with both CI and CP in planta in forming PD-localized complexes during viral infection. Further, we screened HCPro2-associating host proteins, and identified a common host protein in Nicotiana benthamiana-Rubisco small subunit (NbRbCS) that mediates the interactions of HCPro2 with CI or CP, and CI with CP. Knockdown of NbRbCS impairs these interactions, and significantly attenuates the intercellular and systemic movement of ANRSV and three other potyvirids (turnip mosaic virus, pepper veinal mottle virus, and telosma mosaic virus). This study indicates that a nucleus-encoded chloroplast-targeted protein is hijacked by potyvirids as the scaffold protein to assemble a complex to facilitate viral movement across cells.
Topics: Viral Proteins; Ribulose-Bisphosphate Carboxylase; Potyvirus; Plant Diseases
PubMed: 38437247
DOI: 10.1371/journal.ppat.1012064 -
IScience Mar 2024R-β-homoserine (RBH) and β-aminobutyric acid (BABA) induce resistance against the oomycete () in Arabidopsis, which is based on priming of multiple defense layers,...
R-β-homoserine (RBH) and β-aminobutyric acid (BABA) induce resistance against the oomycete () in Arabidopsis, which is based on priming of multiple defense layers, including early acting penetration resistance at the cell wall. Here, we have examined the molecular basis of RBH- and BABA-primed defense by cell wall papillae against . Three-dimensional reconstruction of -induced papillae by confocal microscopy revealed no structural differences between control-, RBH-, and BABA-treated plants after challenge. However, mutations affecting POWDERY MILDEW RESISTANCE 4 or PLASMODESMATA LOCATED PROTEINs (PDLPs) only impaired BABA-induced penetration resistance and not RBH-induced penetration resistance. Furthermore, over-expression mimicked primed penetration resistance, while the intensity of GFP-tagged PDLP1 at germinating conidiospores was increased in BABA-primed plants but not RBH-primed plants. Our study reveals new regulatory layers of immune priming by β-amino acids and supports the notion that penetration resistance is a multifaceted defense layer that can be achieved through seperate pathways.
PubMed: 38482498
DOI: 10.1016/j.isci.2024.109299 -
Virology Oct 2023Over the past decades, several studies have examined the subcellular localization of the cauliflower mosaic virus (CaMV) P6 protein by tagging it with GFP (P6-GFP)....
Transient expression of cauliflower mosaic virus (CaMV) P6-GFP complements a defective CaMV replicon to facilitate viral gene expression, replication and virion formation.
Over the past decades, several studies have examined the subcellular localization of the cauliflower mosaic virus (CaMV) P6 protein by tagging it with GFP (P6-GFP). These investigations have been essential in the development of models for inclusion body formation, nuclear transport, and microfilament-associated intracellular movement of P6 inclusion bodies for delivery of virions to plasmodesmata. Although it was shown early on that the translational transactivation function of P6-GFP was comparable to wild type P6, it has not been possible to incorporate a P6-GFP gene into an infectious clone of CaMV. Consequently, it has not been possible to formally prove that a P6-GFP fusion is comparable in function to the unmodified P6 protein. Here we show that transient expression of P6-GFP can complement a defective CaMV replicon through gene expression, replication and encapsidation, which validates the relevance of P6-GFP subcellular localization studies for understanding the development of CaMV infections.
PubMed: 37556874
DOI: 10.1016/j.virol.2023.109854 -
Molecular Plant Pathology May 2024The movement of potyviruses, the largest genus of single-stranded, positive-sense RNA viruses responsible for serious diseases in crops, is very complex. As potyviruses...
The movement of potyviruses, the largest genus of single-stranded, positive-sense RNA viruses responsible for serious diseases in crops, is very complex. As potyviruses developed strategies to hijack the host secretory pathway and plasmodesmata (PD) for their transport, the goal of this study was to identify membrane and/or PD-proteins that interact with the 6K2 protein, a potyviral protein involved in replication and cell-to-cell movement of turnip mosaic virus (TuMV). Using split-ubiquitin membrane yeast two-hybrid assays, we screened an Arabidopsis cDNA library for interactors of 6K2. We isolated AtHVA22a (Hordeum vulgare abscisic acid responsive gene 22), which belongs to a multigenic family of transmembrane proteins, homologous to Receptor expression-enhancing protein (Reep)/Deleted in polyposis (DP1)/Yop1 family proteins in animal and yeast. HVA22/DP1/Yop1 family genes are widely distributed in eukaryotes, but the role of HVA22 proteins in plants is still not well known, although proteomics analysis of PD fractions purified from Arabidopsis suspension cells showed that AtHVA22a is highly enriched in a PD proteome. We confirmed the interaction between 6K2 and AtHVA22a in yeast, as well as in planta by using bimolecular fluorescence complementation and showed that 6K2/AtHVA22a interaction occurs at the level of the viral replication compartment during TuMV infection. Finally, we showed that the propagation of TuMV is increased when AtHVA22a is overexpressed in planta but slowed down upon mutagenesis of AtHVA22a by CRISPR-Cas9. Altogether, our results indicate that AtHVA22a plays an agonistic effect on TuMV propagation and that the C-terminal tail of the protein is important in this process.
Topics: Potyvirus; Arabidopsis; Arabidopsis Proteins; Plant Diseases; Viral Proteins; Virus Replication; Nicotiana
PubMed: 38767756
DOI: 10.1111/mpp.13466 -
The Plant Cell Mar 2024RNA viruses and viroids replicate with high mutation rates, forming quasispecies, population of variants centered around dominant sequences. The mechanisms governing...
RNA viruses and viroids replicate with high mutation rates, forming quasispecies, population of variants centered around dominant sequences. The mechanisms governing quasispecies remain unclear. Plasmodesmata regulate viroid movement and were hypothesized to impact viroid quasispecies. Here, we sequenced the progeny of potato spindle tuber viroid intermediate (PSTVd-I) strain from mature guard cells lacking plasmodesmal connections and from in vitro-cultivated mesophyll cell protoplasts from systemic leaves of early-infected tomato (Solanum lycopersicum) plants. Remarkably, more variants accumulated in guard cells compared to whole leaves. Similarly, after extended cell culture, we observed more variants in cultivated mesophyll protoplasts. Coinfection and single-cell sequencing experiments demonstrated that the same plant cell can be infected multiple times by the same or different PSTVd sequences. To study the impact of initial population composition on PSTVd-I quasispecies, we conducted coinfections with PSTVd-I and variants. Two inoculum ratios (10:1 or 1:10) established quasispecies with or without PSTVd-I as the master sequence. In the absence of the master sequence, the percentage of novel variants initially increased. Moreover, a 1:1 PSTVd-I/variant RNA ratio resulted in PSTVd-I dominating (>50%), while the variants reached 20%. After PSTVd-I-only infection, the variants reached around 10%, while after variant-only infection, the variants were significantly more than 10%. These results emphasize the role of cell-to-cell communication and initial population composition in shaping PSTVd quasispecies.
Topics: Plant Diseases; Quasispecies; RNA; RNA, Viral; Solanum lycopersicum; Viroids
PubMed: 38252648
DOI: 10.1093/plcell/koae012