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Physiology and Molecular Biology of... Feb 2024Systemic acquired resistance protects plants against a broad spectrum of secondary infections by pathogens. A crucial compound involved in the systemic spread of the... (Review)
Review
Systemic acquired resistance protects plants against a broad spectrum of secondary infections by pathogens. A crucial compound involved in the systemic spread of the threat information after primary pathogen infection is the C9 oxylipin azelaic acid (AZA), a breakdown product of unsaturated C18 fatty acids. AZA is generated during lipid peroxidation in the plastids and accumulates in response to various abiotic and biotic stresses. AZA stimulates the expression of (), and a pool of AZI1 accumulates in the plastid envelope in association with AZA. AZA and AZI1 utilize the symplastic pathway to travel through the plasmodesmata to neighbouring cells to induce systemic stress resistance responses in distal tissues. Here, we describe the synthesis, travel and function of AZA and AZI1 and discuss open questions of signal initiation and propagation.
PubMed: 38623172
DOI: 10.1007/s12298-024-01420-1 -
Molecular Plant Pathology Aug 2023The tomato Tm-2 gene was considered to be one of the most durable resistance genes in agriculture, protecting against viruses of the Tobamovirus genus, such as tomato...
The tomato Tm-2 gene was considered to be one of the most durable resistance genes in agriculture, protecting against viruses of the Tobamovirus genus, such as tomato mosaic virus (ToMV) and tobacco mosaic virus (TMV). However, an emerging tobamovirus, tomato brown rugose fruit virus (ToBRFV), has overcome Tm-2 , damaging tomato production worldwide. Tm-2 encodes a nucleotide-binding leucine-rich repeat (NLR) class immune receptor that recognizes its effector, the tobamovirus movement protein (MP). Previously, we found that ToBRFV MP (MP ) enabled the virus to overcome Tm-2 -mediated resistance. Yet, it was unknown how Tm-2 remained durable against other tobamoviruses, such as TMV and ToMV, for over 60 years. Here, we show that a conserved cysteine (C68) in the MP of TMV (MP ) plays a dual role in Tm-2 activation and viral movement. Substitution of MP amino acid H67 with the corresponding amino acid in MP (C68) activated Tm-2 -mediated resistance. However, replacement of C68 in TMV and ToMV disabled the infectivity of both viruses. Phylogenetic and structural prediction analysis revealed that C68 is conserved among all Solanaceae-infecting tobamoviruses except ToBRFV and localizes to a predicted jelly-roll fold common to various MPs. Cell-to-cell and subcellular movement analysis showed that C68 is required for the movement of TMV by regulating the MP interaction with the endoplasmic reticulum and targeting it to plasmodesmata. The dual role of C68 in viral movement and Tm-2 immune activation could explain how TMV was unable to overcome this resistance for such a long period.
Topics: Tobacco Mosaic Virus; Cysteine; Phylogeny; Tobamovirus; Nicotiana; Plant Viral Movement Proteins
PubMed: 37086003
DOI: 10.1111/mpp.13318 -
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 -
Frontiers in Plant Science 2023Asparagus samples were examined from growing areas of Germany and selected European as well as North, Central and South American countries. Overall, 474 samples were...
Asparagus samples were examined from growing areas of Germany and selected European as well as North, Central and South American countries. Overall, 474 samples were analyzed for Asparagus virus 1 (AV1) using DAS-ELISA. In our survey, 19 AV1 isolates were further characterized. Experimental transmission to 11 species belonging to Aizoaceae, Amarantaceae, Asparagaceae, and Solanaceae succeeded. The ultrastructure of AV1 infection in asparagus has been revealed and has been compared with the one in indicator plants. The cylindrical inclusion (CI) protein, a core factor in viral replication, localized within the cytoplasm and in systemic infections adjacent to the plasmodesmata. The majority of isolates referred to pathotype I (PI). These triggered a hypersensitive resistance in inoculated leaves of spp. and were incapable of infecting spp. Only pathotype II (PII) and pathotype III (PIII) infected systemically but differed in their virulence when transmitted to spp. The newly identified PIII generated amorphous inclusion bodies and degraded chloroplasts during systemic infection but not in local lesions of infected spp. PIII probably evolved recombination in asparagus carrying a mixed infection by PI and PII. Phylogeny of the coat protein region recognized two clusters, which did not overlap with the CI-associated grouping of pathotypes. These results provide evidence for ongoing modular evolution of AV1.
PubMed: 37600206
DOI: 10.3389/fpls.2023.1187563 -
The Plant Journal : For Cell and... Oct 2023Ovules are female reproductive organs of angiosperms, consisting of sporophytic integuments surrounding female gametophytes, that is, embryo sacs. Synchronization...
Ovules are female reproductive organs of angiosperms, consisting of sporophytic integuments surrounding female gametophytes, that is, embryo sacs. Synchronization between integument growth and embryo sac development requires intracellular communication. However, signaling routes through which cells of the two generations communicate are unclear. We report that symplastic signals through plasmodesmata (PDs) of integuments are critical for the development of female gametophytes. Genetic interferences of PD biogenesis either by functional loss of CHOLINE TRANSPORTER-LIKE1 (CTL1) or by integument-specific expression of a mutated CALLOSE SYNTHASE 3 (cals3m) compromised PD formation in integuments and reduced fertility. Close examination of pINO:cals3m or ctl1 ovules indicated that female gametophytic development was either arrested at various stages after the formation of functional megaspores. In both cases, defective ovules could not attract pollen tubes, leading to the failure of fertilization. Results presented here demonstrate a key role of the symplastic route in sporophytic control of female gametophytic development.
Topics: Arabidopsis; Ovule; Arabidopsis Proteins; Fertility; Pollen Tube
PubMed: 37381795
DOI: 10.1111/tpj.16368 -
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 -
Nature Plants Sep 2023In plants, restoring intercellular communication is required for cell activity in buds during the growth transition from slow to fast growth after dormancy release....
In plants, restoring intercellular communication is required for cell activity in buds during the growth transition from slow to fast growth after dormancy release. However, the epigenetic regulation of this phenomenon is far from understood. Here we demonstrate that lily VERNALIZATION INSENSITIVE 3-LIKE 1 (LoVIL1) confers growth transition by mediating plasmodesmata opening via epigenetic repression of CALLOSE SYNTHASE 3 (LoCALS3). Moreover, we found that a novel transcription factor, NUCLEAR FACTOR Y, SUBUNIT A7 (LoNFYA7), is capable of recruiting the LoVIL1-Polycomb Repressive Complex 2 (PRC2) and enhancing H3K27me3 at the LoCALS3 locus by recognizing the CCAAT cis-element (Cce) of its promoter. The LoNFYA7-LoVIL1 module serves as a key player in orchestrating the phase transition from slow to fast growth in lily bulbs. These studies also indicate that LoVIL1 is a suitable marker for the bud-growth-transition trait following dormancy release in lily cultivars.
Topics: Epigenesis, Genetic; Lilium; Glucosyltransferases; Polycomb Repressive Complex 2; Gene Expression Regulation, Plant
PubMed: 37563458
DOI: 10.1038/s41477-023-01492-z -
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 -
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 Biotechnology Journal May 2024Viral diseases seriously threaten rice production. Plasmodesmata (PD)-associated proteins are deemed to play a key role in viral infection in host plants. However, few...
Viral diseases seriously threaten rice production. Plasmodesmata (PD)-associated proteins are deemed to play a key role in viral infection in host plants. However, few PD-associated proteins have been discovered in rice to afford viral infection. Here, inspired by the infection mechanism in insect vectors, we identified a member of the Flotillin family taking part in the cell-to-cell transport of rice stripe virus (RSV) in rice. Flotillin1 interacted with RSV nucleocapsid protein (NP) and was localized on PD. In flotillin1 knockout mutant rice, which displayed normal growth, RSV intercellular movement was retarded, leading to significantly decreased disease incidence. The PD pore sizes of the mutant rice were smaller than those of the wild type due to more callose deposits, which was closely related to the upregulation of two callose synthase genes. RSV infection stimulated flotillin1 expression and enlarged the PD aperture via RSV NP. In addition, flotillin1 knockout decreased disease incidences of southern rice black-streaked dwarf virus (SRBSDV) and rice dwarf virus (RDV) in rice. Overall, our study reveals a new PD-associated protein facilitating virus cell-to-cell trafficking and presents the potential of flotillin1 as a target to produce broad-spectrum antiviral rice resources in the future.
Topics: Animals; Plasmodesmata; Viral Proteins; Virus Diseases; Oryza; Plant Diseases; Hemiptera; Membrane Proteins
PubMed: 38130080
DOI: 10.1111/pbi.14274