Plant Pathogen Response Research Articles

Sphingolipid homeostasis--how do cells know when enough is enough? Implications for plant pathogen responses.

Sphingolipid homeostatic regulation is important for balancing plant life and death. Plant cells finely tune sphingolipid biosynthesis to ensure sufficient levels to support growth through their basal functions as major components of endomembranes and the plasma membrane. Conversely, accumulation of sphingolipid biosynthetic intermediates, long-chain bases (LCBs) and ceramides, is associated with programmed cell death (PCD). Limiting these apoptotic intermediates is important for cell viability; while overriding homeostatic regulation permits cells to generate elevated LCBs and ceramides to respond to pathogens to elicit the hypersensitive response in plant immunity. Key to sphingolipid homeostasis is serine palmitoyltransferase (SPT), an ER-associated, multi-subunit enzyme catalyzing the first step in the biosynthesis of LCBs, the defining feature of sphingolipids. Across eukaryotes, SPT interaction with its negative regulator ORM is critical for sphingolipid biosynthesis. The recent cryo-electron microscopy structure of the Arabidopsis SPT complex indicates that ceramides bind ORMs to competitively inhibit SPT activity. This system provides a sensor for intracellular ceramide concentrations for sphingolipid homeostatic regulation. Combining the newly elucidated Arabidopsis SPT structure and mutant characterization, we present a model for the role of the two functionally divergent Arabidopsis ceramide synthase classes to produce ceramides that form repressive (trihydroxy LCB-ceramides) or non-repressive (dihydroxy LCB-ceramides) ORM interactions to influence SPT activity. We describe how sphingolipid biosynthesis is regulated by the interplay of ceramide synthases with ORM-SPT when "enough is enough" and override homeostatic suppression when "enough is not enough" to respond to environmental stimuli such as microbial pathogen attack.

A systematic analysis of ARM genes revealed that GhARM144 regulates the resistance against Verticillium dahliae via interaction with GhOSM34.

Proteins of the armadillo repeat gene family play important roles in plant pathogen response. Here, 169 armadillo (ARM) genes were identified in upland cotton (Gossypium hirsutum). Phylogenetic analysis grouped these into 11 subfamilies, with conserved protein structures within each subfamily. The results signify that the expansion of the gene family occurred via whole genome duplication and dispersed duplication. Expression profiling and network analysis suggest that GhARM144 may regulate cotton resistance to Verticillium dahliae. GhARM144 was upregulated in roots by V. dahliae infection or salicylic acid treatment. This upregulation indicates a negative regulatory role of GhARM144' in the cotton immune responses, potentially by manipulating salicylic acid biosynthesis. Protein interaction studies found that GhARM144 associates with an osmotin-like protein, GhOSM34, at the plasma membrane. Silencing GhOSM34 reduced the resistance to V. dahliae, suggesting it may play a positive regulatory role. The results demonstrate that GhARM144 modulates cotton immunity through interaction with GhOSM34 and salicylic acid signalling. Further study of these proteins may yield insights into disease resistance mechanisms in cotton and other plants.

Genome-Wide Identification and Expression Profiling of Potato (Solanum tuberosum L.) Universal Stress Proteins Reveal Essential Roles in Mechanical Damage and Deoxynivalenol Stress.

Universal stress proteins (USPs) play an important regulatory role in responses to abiotic stress. Most of the research related to USPs so far has been conducted on plant models such as Arabidopsis (Arabidopsis thaliana), rice (Oryza sativa L.), and cotton (Gossypium hirsutum L.). The potato (Solanum tuberosum L.) is one of the four major food crops in the world. The potato is susceptible to mechanical damage and infection by pathogenic fungi during transport and storage. Deoxynivalenol (DON) released by Fusarium can seriously degrade the quality of potatoes. As a result, it is of great significance to study the expression pattern of the potato StUSP gene family under abiotic stress conditions. In this study, a total of 108 USP genes were identified from the genome of the Atlantic potato, divided into four subgroups. Based on their genetic structure, the physical and chemical properties of their proteins and other aspects of their biological characteristics are comprehensively analyzed. Collinear analysis showed that the homologous genes of StUSPs and four other representative species (Solanum lycopersicum, Arabidopsis, Oryza sativa L., and Nicotiana attenuata) were highly conserved. The cis-regulatory elements of the StUSPs promoter are involved in plant hormones, environmental stress, mechanical damage, and light response. RNA-seq analysis showed that there are differences in the expression patterns of members of each subgroup under different abiotic stresses. A Weighted Gene Coexpression Network Analysis (WGCNA) of the central gene showed that the differential coexpression gene is mainly involved in the plant-pathogen response process, plant hormone signal transduction, and the biosynthesis process of secondary metabolites. Through qRT-PCR analysis, it was confirmed that StUSP13, StUSP14, StUSP15, and StUSP41 may be important candidate genes involved in the response to adversity stress in potatoes. The results of this study provide a basis for further research on the functional analysis of StUSPs in the response of potatoes to adversity stress.

Temperature sensitivity of soil-borne fungal phytopathogens depends on niche breadth and land use types

Soil-borne fungal plant pathogens pose great threats to agricultural productivity and native ecosystems. However, the roles of niche breadth and land-use types in regulating the response of soil-borne fungal plant pathogens to temperature changes largely remain unclear. Here, we surveyed soil pathogens from different valleys where croplands, grasslands, and woodlands scattered in mosaic patterns. We found that pathogen richness increased with increasing temperature in grasslands but not in croplands and woodlands. After classifying the pathogens based on temperature niche, we found that the richness of specialists was sensitive to temperature changes and increased with increasing temperature in grasslands and croplands. By contrast, the richness of neutrals (those taxa not defined as generalists or specialists) did not change with temperature gradients regardless of land-use types. Additionally, pathogens were more abundant and diverse in croplands than those in grasslands and woodlands, and this pattern persisted across the temperature gradient. Our results provide evidence that temperature change and land use types could additively affect the diversity of plant pathogens in soils. This work advances our understanding of how niche breadth affects the response of pathogens to temperature, highlighting the importance of climate change and land use in regulating the abundance and diversity of pathogens.

Characterization of the soybean KRP gene family reveals a key role for GmKRP2a in root development.

Kip-related proteins (KRPs), as inhibitory proteins of cyclin-dependent kinases, are involved in the growth and development of plants by regulating the activity of the CYC-CDK complex to control cell cycle progression. The KRP gene family has been identified in several plants, and several KRP proteins from Arabidopsis thaliana have been functionally characterized. However, there is little research on KRP genes in soybean, which is an economically important crop. In this study, we identified nine GmKRP genes in the Glycine max genome using HMM modeling and BLASTP searches. Protein subcellular localization and conserved motif analysis showed soybean KRP proteins located in the nucleus, and the C-terminal protein sequence was highly conserved. By investigating the expression patterns in various tissues, we found that all GmKRPs exhibited transcript abundance, while several showed tissue-specific expression patterns. By analyzing the promoter region, we found that light, low temperature, an anaerobic environment, and hormones-related cis-elements were abundant. In addition, we performed a co-expression analysis of the GmKRP gene family, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) set enrichment analysis. The co-expressing genes were mainly involved in RNA synthesis and modification and energy metabolism. Furthermore, the GmKRP2a gene, a member of the soybean KRP family, was cloned for further functional analysis. GmKRP2a is located in the nucleus and participates in root development by regulating cell cycle progression. RNA-seq results indicated that GmKRP2a is involved in cell cycle regulation through ribosome regulation, cell expansion, hormone response, stress response, and plant pathogen response pathways. To our knowledge, this is the first study to identify and characterize the KRP gene family in soybean.

Integrated Transcriptome and Metabolome Analysis to Identify Sugarcane Gene Defense against Fall Armyworm (Spodoptera frugiperda) Herbivory.

Sugarcane is the most important sugar crop, contributing ≥80% to total sugar production around the world. Spodoptera frugiperda is one of the main pests of sugarcane, potentially causing severe yield and sugar loss. The identification of key defense factors against S. frugiperda herbivory can provide targets for improving sugarcane resistance to insect pests by molecular breeding. In this work, we used one of the main sugarcane pests, S. frugiperda, as the tested insect to attack sugarcane. Integrated transcriptome and metabolomic analyses were performed to explore the changes in gene expression and metabolic processes that occurred in sugarcane leaf after continuous herbivory by S. frugiperda larvae for 72 h. The transcriptome analysis demonstrated that sugarcane pest herbivory enhanced several herbivory-induced responses, including carbohydrate metabolism, secondary metabolites and amino acid metabolism, plant hormone signaling transduction, pathogen responses, and transcription factors. Further metabolome analysis verified the inducement of specific metabolites of amino acids and secondary metabolites by insect herbivory. Finally, association analysis of the transcriptome and metabolome by the Pearson correlation coefficient method brought into focus the target defense genes against insect herbivory in sugarcane. These genes include amidase and lipoxygenase in amino acid metabolism, peroxidase in phenylpropanoid biosynthesis, and pathogenesis-related protein 1 in plant hormone signal transduction. A putative regulatory model was proposed to illustrate the sugarcane defense mechanism against insect attack. This work will accelerate the dissection of the mechanism underlying insect herbivory in sugarcane and provide targets for improving sugarcane variety resistance to insect herbivory by molecular breeding.

How do emerging long-read sequencing technologies function in transforming the plant pathology research landscape?

Long-read sequencing technologies are revolutionizing the sequencing and analysis of plant and pathogen genomes and transcriptomes, as well as contributing to emerging areas of interest in plant-pathogen interactions, disease management techniques, and the introduction of new plant varieties or cultivars. Long-read sequencing (LRS) technologies are progressively being implemented to study plants and pathogens of agricultural importance, which have substantial economic effects. The variability and complexity of the genome and transcriptome affect plant growth, development and pathogen responses. Overcoming the limitations of second-generation sequencing, LRS technology has significantly increased the length of a single contiguous read from a few hundred to millions of base pairs. Because of the longer read lengths, new analysis methods and tools have been developed for plant and pathogen genomics and transcriptomics. LRS technologies enable faster, more efficient, and high-throughput ultralong reads, allowing direct sequencing of genomes that would be impossible or difficult to investigate using short-read sequencing approaches. These benefits include genome assembly in repetitive areas, creating more comprehensive and exact genome determinations, assembling full-length transcripts, and detecting DNA and RNA alterations. Furthermore, these technologies allow for the identification of transcriptome diversity, significant structural variation analysis, and direct epigenetic mark detection in plant and pathogen genomic regions. LRS in plant pathology is found efficient for identifying and characterization of effectors in plants as well as known and unknown plant pathogens. In this review, we investigate how these technologies are transforming the landscape of determination and characterization of plant and pathogen genomes and transcriptomes efficiently and accurately. Moreover, we highlight potential areas of interest offered by LRS technologies for future study into plant-pathogen interactions, disease control strategies, and the development of new plant varieties or cultivars.

Overexpression of the Arabidopsis MACPF Protein AtMACP2 Promotes Pathogen Resistance by Activating SA Signaling.

Immune response in plants is tightly regulated by the coordination of the cell surface and intracellular receptors. In animals, the membrane attack complex/perforin-like (MACPF) protein superfamily creates oligomeric pore structures on the cell surface during pathogen infection. However, the function and molecular mechanism of MACPF proteins in plant pathogen responses remain largely unclear. In this study, we identified an Arabidopsis MACP2 and investigated the responsiveness of this protein during both bacterial and fungal pathogens. We suggest that MACP2 induces programmed cell death, bacterial pathogen resistance, and necrotrophic fungal pathogen sensitivity by activating the biosynthesis of tryptophan-derived indole glucosinolates and the salicylic acid signaling pathway dependent on the activity of enhanced disease susceptibility 1 (EDS1). Moreover, the response of MACP2 mRNA isoforms upon pathogen attack is differentially regulated by a posttranscriptional mechanism: alternative splicing. In comparison to previously reported MACPFs in Arabidopsis, MACP2 shares a redundant but nonoverlapping role in plant immunity. Thus, our findings provide novel insights and genetic tools for the MACPF family in maintaining SA accumulation in response to pathogens in Arabidopsis.

Detection and Imaging of the Plant Pathogen Response By Near Infrared Fluorescent Polyphenol Sensors

Plants use secondary metabolites such as polyphenols for chemical defense against pathogens and herbivores. Despite their importance in plant pathogen interactions and tolerance to diseases, it remains challenging to detect polyphenols in complex plant tissues. Here, we create molecular sensors for plant polyphenol imaging that are based on near-infrared (NIR) fluorescent single wall carbon nanotubes (SWCNTs). We identified polyethylene glycol-phospholipids that render (6,5)-SWCNTs sensitive (Kd = 90 nM) to plant polyphenols (tannins, flavonoids, ...), which red-shift (up to 20 nm) and quench their emission (~1000 nm). These sensors report changes in total polyphenol level after herbivore or pathogen challenge in crop plant systems (Soybean Glycine max) and leaf tissue extracts (Tococa spp). We furthermore demonstrate remote chemical imaging of pathogen-induced polyphenol release from roots of soybean seedlings over the time course of 24h. Additional use of chirality-pure polyphenol sensors gives further access to ratiometric sensing and imaging applications. Overall, this approach allows in situ visualization and understanding of the chemical plant defense in real time and paves the way for plant phenotyping for optimized polyphenol secretion.

Evolution of substrate specificity in a maize anthranilate methyltransferase

Secondary metabolites play a key role in mediating pollination and plant defense against herbivory. One such metabolite, methyl anthranilate, is a volatile compound responsible for the recognizable scent of Concord grapes. Methyl anthranilate is commercially used as a bird repellent for golf courses and as a flavoring agent for grape‐flavored foods, beverages, and pharmaceuticals. A variety of plant species such as Zea mays (maize) and Vitis labrusca (fox grape) synthesize methyl anthranilate from anthranilate, an intermediate in tryptophan biosynthesis. Methyl anthranilate biosynthesis is a classic example of convergent evolution; in maize, this reaction is catalyzed by an anthranilate methyltransferase (AAMT1), while in grape, there is a two‐step pathway. Previous studies have found that the ZmAAMT1 SABATH methyltransferase likely evolved from methyltransferases that recognize the plant pathogen response hormone salicylic acid as a substrate. Using site‐directed mutagenesis, we introduced 12 independent missense mutations at 7 key active site residues with the intention of restoring substrate specificity for salicylic acid. This work will allow us to better trace and understand the evolution of anthranilate‐derived specialized metabolism in plants.

Organic fertilization regimes suppress fungal plant pathogens through modulating the resident bacterial and protistan communities

AbstractIntroductionFungal plant pathogens are an emerging threat to economically important crop production worldwide and a significant risk to global food security. However, we have limited knowledge of how agricultural management practices drive the emergence and spread of pathogens within crop microbiomes and the underlying ecological mechanisms.Materials and MethodsWe characterized the profiles of potential fungal plant pathogens, as well as bacterial and protistan communities, in sorghum phyllosphere, root endosphere, and rhizosphere and bulk soils collected from a long‐term experiment with multiple inorganic and organic fertilization regimes.ResultsWe found contrasting patterns of fungal plant pathogens across the four sorghum–soil compartments and that organic fertilization regime significantly reduced the diversity and proportions of fungal plant pathogens in rhizosphere and bulk soils. We further found that the changes in fungal plant pathogens were driven more by resident bacterial and protistan communities than by soil physicochemical parameters. There was a significantly negative relationship between the diversity of fungal plant pathogens in the rhizosphere and bulk soils with sorghum yield and protein contents. Structural equation modeling revealed that long‐term organic fertilization regimes contributed to the suppression of fungal plant pathogens mainly through modulating the resident bacterial and protistan communities.ConclusionThese findings advance our understanding of the responses of fungal plant pathogens in crop microbiomes to fertilization regimes, with implications for more targeted strategies to manage the impacts of fungal pathogens on plant health and economic losses.

Long Non-Coding RNAs as Emerging Regulators of Pathogen Response in Plants.

Long non-coding RNAs (lncRNAs) are transcripts without protein-coding potential that contain more than 200 nucleotides that play important roles in plant survival in response to different stresses. They interact with molecules such as DNA, RNA, and protein, and play roles in the regulation of chromatin remodeling, RNA metabolism, and protein modification activities. These lncRNAs regulate the expression of their downstream targets through epigenetic changes, at the level of transcription and post-transcription. Emerging information from computational biology and functional characterization of some of them has revealed their diverse mechanisms of action and possible roles in biological processes such as flowering time, reproductive organ development, as well as biotic and abiotic stress responses. In this review, we have mainly focused on the role of lncRNAs in biotic stress response due to the limited availability of knowledge in this domain. We have discussed the available molecular mechanisms of certain known lncRNAs against specific pathogens. Further, considering that fungal, viral, and bacterial diseases are major factors in the global food crisis, we have highlighted the importance of lncRNAs against pathogen responses and the progress in plant research to develop a better understanding of their functions and molecular mechanisms.

Frontispiece: Detection and Imaging of the Plant Pathogen Response by Near‐Infrared Fluorescent Polyphenol Sensors

Biosensors Molecular sensors for plant polyphenol imaging based on near-infrared fluorescent single wall carbon nanotubes are presented by Sebastian Kruss et al. in their Research Article (e202108373).

Detektion und Visualisierung der Pflanzen‐Pathogen‐Response durch Nah‐Infrarot‐fluoreszente Polyphenolsensoren

AbstractPflanzen nutzen Sekundärmetabolite, wie Polyphenole, zur chemischen Verteidigung gegenüber Pathogenen und Herbivoren. Trotz ihrer wichtigen Rolle bei der Reaktion von Pflanzen auf Pathogene bleibt die Detektion von Polyphenolen in komplexen Pflanzengeweben eine Herausforderung. Hier berichten wir vom Aufbau molekularer Sensoren zur Visualisierung pflanzlicher Polyphenole, basierend auf Nah‐Infrarot (NIR)‐fluoreszenten Kohlenstoff‐Nanoröhren (SWCNTs). Dabei identifizierten wir Oberflächenmodifikationen mit Polyethylenglycol‐Phospholipiden, die (6,5)‐SWCNTs sensitiv (Kd=90 nM) gegenüber pflanzlichen Polyphenolen machen und die Emission (ca. 1000 nm) quenchen und bathochrom (bis zu 20 nm) verschieben. Diese Sensoren detektieren Unterschiede im Gesamtphenolgehalt nach Herbivor‐ oder Pathogenstimulus im Nutzpflanzensystem und in Blattextrakten. Ferner erlauben sie die Bildgebung der Pathogen‐induzierten Polyphenolausschüttung (24 h). Dieser Ansatz ermöglicht die In‐situ‐Visualisierung und Charakterisierung der chemischen Pflanzenverteidigung in Echtzeit und ebnet den Weg zur Phänotyp‐basierten Optimierung der Polyphenolsekretion.

Detection and Imaging of the Plant Pathogen Response by Near-Infrared Fluorescent Polyphenol Sensors.

Plants use secondary metabolites such as polyphenols for chemical defense against pathogens and herbivores. Despite their importance in plant pathogen interactions and tolerance to diseases, it remains challenging to detect polyphenols in complex plant tissues. Here, we create molecular sensors for plant polyphenol imaging that are based on near‐infrared (NIR) fluorescent single‐wall carbon nanotubes (SWCNTs). We identified polyethylene glycol–phospholipids that render (6,5)‐SWCNTs sensitive (Kd=90 nM) to plant polyphenols (tannins, flavonoids, …), which red‐shift (up to 20 nm) and quench their emission (ca. 1000 nm). These sensors report changes in total polyphenol level after herbivore or pathogen challenge in crop plant systems (Soybean Glycine max) and leaf tissue extracts (Tococa spp.). We furthermore demonstrate remote chemical imaging of pathogen‐induced polyphenol release from roots of soybean seedlings over the time course of 24 h. This approach allows in situ visualization and understanding of the chemical plant defense in real time and paves the way for plant phenotyping for optimized polyphenol secretion.

Glyoxalase I-4 functions downstream of NAC72 to modulate downy mildew resistance in grapevine.

Glyoxalase I (GLYI) is part of the glyoxalase system; its major function is the detoxification of α-ketoaldehydes, including the potent and cytotoxic methylglyoxal (MG). Methylglyoxal disrupts mitochondrial respiration and increases production of reactive oxygen species (ROS), which also increase during pathogen infection of plant tissues; however, there have been few studies relating the glyoxalase system to the plant pathogen response. We used the promoter of VvGLYI-4 to screen the upstream transcription factors and report a NAC (NAM/ATAF/CUC) domain-containing transcription factor VvNAC72 in grapevine, which is localized to the nucleus. Our results show that VvNAC72 expression is induced by downy mildew, Plasmopara viticola, while the transcript level of VvGLYI-4 decreases. Further analysis revealed that VvNAC72 can bind directly to the promoter region of VvGLYI-4 via the CACGTG element, leading to inhibition of VvGLYI-4 transcription. Stable overexpression of VvNAC72 in grapevine and tobacco showed a decreased expression level of VvGLYI-4 and increased content of MG and ROS, as well as stronger resistance to pathogen stress. Taken together, these results demonstrate that grapevine VvNAC72 negatively modulates detoxification of MG through repression of VvGLYI-4, and finally enhances resistance to downy mildew, at least in part, via the modulation of MG-associated ROS homeostasis through a salicylic acid-mediated defense pathway.

Transcriptomics of different tissues of blueberry and diversity analysis of rhizosphere fungi under cadmium stress

Blueberry (Vaccinium ssp.) is a perennial shrub belonging to the family Ericaceae, which is highly tolerant of acid soils and heavy metal pollution. In the present study, blueberry was subjected to cadmium (Cd) stress in simulated pot culture. The transcriptomics and rhizosphere fungal diversity of blueberry were analyzed, and the iron (Fe), manganese (Mn), copper (Cu), zinc (Zn) and cadmium (Cd) content of blueberry tissues, soil and DGT was determined. A correlation analysis was also performed. A total of 84 374 annotated genes were identified in the root, stem, leaf and fruit tissue of blueberry, of which 3370 were DEGs, and in stem tissue, of which 2521 were DEGs. The annotation data showed that these DEGs were mainly concentrated in a series of metabolic pathways related to signal transduction, defense and the plant–pathogen response. Blueberry transferred excess Cd from the root to the stem for storage, and the highest levels of Cd were found in stem tissue, consistent with the results of transcriptome analysis, while the lowest Cd concentration occurred in the fruit, Cd also inhibited the absorption of other metal elements by blueberry. A series of genes related to Cd regulation were screened by analyzing the correlation between heavy metal content and transcriptome results. The roots of blueberry rely on mycorrhiza to absorb nutrients from the soil. The presence of Cd has a significant effect on the microbial community composition of the blueberry rhizosphere. The fungal family Coniochaetaceae, which is extremely extremelytolerant, has gradually become the dominant population. The results of this study increase our understanding of the plant regulation mechanism for heavy metals, and suggest potential methods of soil remediation using blueberry.

A complex interplay of Gβ and Gγ proteins regulates plant growth and defence traits in the allotetraploid Brassica juncea.

Gene expression analysis coupled with in-planta studies showed that specific Gβγ combination regulates plant growth and defence traits in the allotetraploid Brassica juncea. Plant heterotrimeric G-proteins regulate a wide range of responses despite their limited repertoire of core components. The roles and functional interactions between different G-protein subunits are quite perplexing, which get further complicated with polyploidy. Here, we show that the allotetraploid Brassica juncea comprises multiple homologs of G-protein genes, encoding six BjuGβ and ten highly divergent BjuGγ subunit proteins, later being classified into type-A1, type-A2 and type-C Gγ proteins. The encoded BjuGβ and BjuGγ proteins shared close evolutionary relationship and have retained distinct spatio-temporal expression patterns during plant developmental stages and in response to the necrotrophic pathogen, Sclerotinia sclerotiorum. RNAi based suppression of BjuGβ and BjuGγ genes suggested functional overlap and selectivity of BjuGβs with three distinct BjuGγ type subunits, to regulate plant height (BjuGβγA2 and BjuGβγC), seed weight (BjuGβGγA1 and BjuGβGγC), silique size (BjuGβGγC) and pathogen response (BjuGβGγA1 and BjuGβGγC). Further, the triplicated BjuGβ genes, formed due to Brassica specific whole-genome-triplication event, showed differential involvement during pathogen response, wherein overexpression of BjuGβ2 displayed higher resistance to Sclerotinia infection. Taken together, our study demonstrates that multiple BjuGβ and BjuGγ proteins have retained distinct spatio-temporal expression and functional selectivity to regulate specific plant growth and defence traits in the oilseed B. juncea.

Large tandem duplications affect gene expression, 3D organization, and plant-pathogen response.

Rapid plant genome evolution is crucial to adapt to environmental changes. Chromosomal rearrangements and gene copy number variation (CNV) are two important tools for genome evolution and sources for the creation of new genes. However, their emergence takes many generations. In this study, we show that in Arabidopsis thaliana, a significant loss of ribosomal RNA (rRNA) genes with a past history of a mutation for the chromatin assembly factor 1 (CAF1) complex causes rapid changes in the genome structure. Using long-read sequencing and microscopic approaches, we have identified up to 15 independent large tandem duplications in direct orientation (TDDOs) ranging from 60 kb to 1.44 Mb. Our data suggest that these TDDOs appeared within a few generations, leading to the duplication of hundreds of genes. By subsequently focusing on a line only containing 20% of rRNA gene copies (20rDNA line), we investigated the impact of TDDOs on 3D genome organization, gene expression, and cytosine methylation. We found that duplicated genes often accumulate more transcripts. Among them, several are involved in plant–pathogen response, which could explain why the 20rDNA line is hyper-resistant to both bacterial and nematode infections. Finally, we show that the TDDOs create gene fusions and/or truncations and discuss their potential implications for the evolution of plant genomes.

Sensing Attack: The Role of Wall-Associated Kinases in Plant Pathogen Responses.

The physical and chemical barrier provided by the cell wall is one of the first lines of defense against pathogen attack for plants. Plant cell walls provide physical protection against biotic and abiotic stresses but are also involved in a sophisticated sensing system for detecting both microbe-