Defended to the Nines: 25 Years of Resistance Gene Cloning Identifies Nine Mechanisms for R Protein Function

Metabolomic datasets of an apple progeny carrying resistance quantitative trait loci to apple scab before or after inoculation of the pathogen Venturia inaequalis

Phytosanitary treatments are massively used in orchards to fight apple scab, a disease caused by the fungus Venturia inaequalis (Vi). To reduce these treatments, resistant varieties are largely deployed but their effectiveness can decrease over time. The combination of complementary molecular mechanisms within new varieties could enhance the durability of genetic resistance however, the underlying resistance mechanisms remain poorly understood. An apple pseudo-F1 progeny was previously widely investigated for its quantitative trait loci (QTL) controlling resistance to scab and at least three of them seem to act complementarily; notably, one of them is specific to some Vi isolates while the others have a broader spectra of action. The aim of this approach is to better understand the underlying molecular mechanisms and metabolites associated with resistance alleles by exploring apple leaf specialized metabolism. A total of three experiments was conducted: one experiment included non-inoculated leaves whereas in the two other experiments, leaf samples were collected five days after inoculation with two different Vi isolates, including one known to overcome one QTL. Metabolic content was extracted in aqueous methanol before performing an untargeted metabolomic analysis using an Orbitrap IDXTM mass spectrometer, allowing high-resolution mass spectrometry (HRMS) detection. This approach without a priori enables the detection of potentially new chemical families involved in resistance to apple scab. The current data article includes 1) the protocol of plant sample production with a table summarizing key elements of the experimental designs, 2) overview of the raw metabolomic profiles from all three experiments and 3) assessment of metabolic feature reproducibility between replicates in each dataset through Principal Component Analysis. The raw data files are available on the recherche.data.gouv repository (10.57745/XJBD8V). These datasets are valuable resources to further investigate the molecular mechanisms underlying genetic resistance to apple scab, with a focus on specialized metabolism. In the long term, it should improve apple breeding strategies by informing on how to combine appropriate genetic and biochemical factors in new varieties to ensure a more durable resistance.

Genome sequencing of a novel Verticillium dahliae strain (huangweibingjun)

Verticillium dahliae is a soilborne pathogenic fungus that causes vascular discoloration and wilting in a broad spectrum of plant hosts, affecting about 400 species, such as cotton, potatoes, watermelon, cucumber, spinach, etc. In 2021, V. dahliae was estimated to cause about 15-20% reduction in cotton in China. Here, we report the genome sequencing of a novel strain named huangweibingjun, isolated from diseased cotton roots in the Henan province of China. The huangweibingjun genome consists of a total size of 35.84 Mb, GC content of 59.835%, and harbors six chromosomes (scaffold7561, scaffold7329, scaffold7795, scaffold5491, scaffold5473, and scaffold4511). The genome architecture showed a high diversity of cell wall-degrading secretory proteins that might influence the pathogenicity of the fungal strain. Moreover, preliminary metabolic pathway prediction showed that this novel strain synthesizes polyketide, terpenoids, shikimic acid-derived compounds and could also be aflatoxigenic. Consistent with other pathogenic microbes, the huangweibingjun genome comprises several virulent-associated genes. This genome assembly lays the foundation for further investigation of the pathogenicity of huangweibingjun.

Progress and innovations of gene cloning in wheat and its close relatives

KEY MESSAGE

Wheat and its close relatives have large and complex genomes, making gene cloning difficult. Nevertheless, developments in genomics over the past decade have made it more feasible. The large and complex genomes of cereals, especially bread wheat, have always been a challenge for gene mapping and cloning. Nevertheless, recent advances in genomics have led to significant progress in this field. Currently, high-quality reference sequences are available for major wheat species and their relatives. New high-throughput genotyping platforms and next-generation sequencing technologies combined with genome complexity reduction techniques and mutagenesis have opened new avenues for gene cloning. In this review, we provide a comprehensive overview of the genes cloned in wheat so far and discuss the strategies used for cloning these genes. We highlight the advantages and drawbacks of individual approaches and show how particular genomic progress contributed to wheat gene cloning. A wide range of new resources and approaches have led to a significant increase in the number of successful cloning projects over the past decade, demonstrating that it is now feasible to perform rapid gene cloning of agronomically important genes, even in a genome as large and complex as that of wheat.

Reciprocal phosphorylation between SOAK1 and SOBIR1 fine-tunes receptor-like protein (RLP)-mediated plant immunity

SUPPRESSOR OF BIR1-1 (SOBIR1) is a receptor-like kinase (RLK) that acts as a coreceptor for multiple receptor-like proteins (RLPs) to mediate pathogen-associated molecular pattern)-triggered immunity. However, the regulation of SOBIR1 homeostasis and activity remains largely unknown. Our study reveals that SOBIR1-ASSOCIATED PROTEIN KINASE 1 (SOAK1), a member of the receptor-like cytoplasmic kinase (RLCK)-V subfamily with a transmembrane domain, negatively regulates multiple RLP-mediated immune responses. SOAK1 constitutively interacts with SOBIR1 and modulates SOBIR1-dependent immune signaling. SOAK1 directly phosphorylates SOBIR1 at serine-406, substantially impairing its ability to transphosphorylate itself and BAK1. The conservation of serine-406 residue among various flowering plants suggests that phosphorylation at this site plays a critical role in regulating plant immunity. Conversely, SOBIR1 also phosphorylates SOAK1 primarily at serine-73, inhibiting SOAK1's kinase activity and derepressing SOBIR1 activity. This study elucidates a regulatory mechanism for SOBIR1 activity and highlights an uncharacterized role of RLCK-V subfamily members in plant immunity.

Epidermal electronic-tattoo for plant immune response monitoring

Real-time monitoring of plant immune responses is crucial for understanding plant immunity and mitigating economic losses from pathogen and pest attacks. However, current methods relying on molecular-level assessment are destructive and time-consuming. Here, we report an ultrathin, substrate-free, and highly conductive electronic tattoo (e-tattoo) designed for plants, enabling immune response monitoring through non-invasive electrical impedance spectroscopy (EIS). The e-tattoo's biocompatibility, high conductivity, and sub-100 nm thickness allow it to conform to leaf tissue morphology and provide robust impedance data. We demonstrate continuous EIS analysis of live transgenic Arabidopsis thaliana plants for over 24 h, capturing the onset of NLR-mediated acute immune responses within three hours post-induction, prior to visible symptoms. RNA-seq and tissue ion leakage tests validate that EIS data accurately represent the physiological and molecular changes associated with immune activation. This non-invasive tissue-assessment technology has the potential to enhance our comprehension of immune activation mechanisms in plants and paves the way for real-time monitoring for plant health management.

Endophytic and Rhizospheric Microorganisms: An Alternative for Sustainable, Organic, and Regenerative Bioinput Formulations for Modern Agriculture

Large amounts of chemical fertilizers are still used to suppress pathogens and boost agricultural productivity and food generation. However, their use can cause harmful environmental imbalance. Furthermore, plants typically absorb limited amounts of the nutrients provided by chemical fertilizers. Recent studies are recommending the use of microbiota present in the soil in different formulations, considering that several microorganisms are found in nature in association with plants in a symbiotic, antagonistic, or synergistic way. This ecological alternative is positive because no undesirable significant alterations occur in the environment while stimulating plant nutrition development and protection against damage caused by control pathogens. Therefore, this review presents a comprehensive discussion regarding endophytic and rhizospheric microorganisms and their interaction with plants, including signaling and bio-control processes concerning the plant's defense against pathogenic spread. A discussion is provided about the importance of these bioinputs as a microbial resource that promotes plant development and their sustainable protection methods aiming to increase resilience in the agricultural system. In modern agriculture, the manipulation of bioinputs through Rhizobium contributes to reducing the effects of greenhouse gases by managing nitrogen runoff and decreasing nitrous oxide. Additionally, mycorrhizal fungi extend their root systems, providing plants with greater access to water and nutrients.

Helper NLR immune protein NRC3 evolved to evade inhibition by a cyst nematode virulence effector

Parasites can counteract host immunity by suppressing nucleotide binding and leucine-rich repeat (NLR) proteins that function as immune receptors. We previously showed that a cyst nematode virulence effector SPRYSEC15 (SS15) binds and inhibits oligomerisation of helper NLR proteins in the expanded NRC1/2/3 clade by preventing intramolecular rearrangements required for NRC oligomerisation into an activated resistosome. Here we examined the degree to which NRC proteins from multiple Solanaceae species are sensitive to suppression by SS15 and tested hypotheses about adaptive evolution of the binding interface between the SS15 inhibitor and NRC proteins. Whereas all tested orthologs of NRC2 were inhibited by SS15, some natural variants of NRC1 and NRC3 are insensitive to SS15 suppression. Ancestral sequence reconstruction combined with functional assays revealed that NRC3 transitioned from an ancestral suppressed form to an insensitive one over 19 million years ago. Our analyses revealed the evolutionary trajectory of an NLR immune receptor against a parasite inhibitor, identifying key evolutionary transitions in helper NLRs that counteract this inhibition. This work reveals a distinct type of gene-for-gene interaction between parasite or pathogen immunosuppressors and host immune receptors that contrasts with the coevolution between AVR effectors and immune receptors.

In silico prediction method for plant Nucleotide-binding leucine-rich repeat- and pathogen effector interactions

Plant Nucleotide-binding leucine-rich repeat (NLR) proteins play a crucial role in effector recognition and activation of Effector triggered immunity following pathogen infection. Genome sequencing advancements have led to the identification of a myriad of NLRs in numerous agriculturally important plant species. However, deciphering which NLRs recognize specific pathogen effectors remains challenging. Predicting NLR-effector interactions in silico will provide a more targeted approach for experimental validation, critical for elucidating function, and advancing our understanding of NLR-triggered immunity. In this study, NLR-effector protein complex structures were predicted using AlphaFold2-Multimer for all experimentally validated NLR-effector interactions reported in literature. Binding affinities- and energies were predicted using 97 machine learning models from Area-Affinity. We show that AlphaFold2-Multimer predicted structures have acceptable accuracy and can be used to investigate NLR-effector interactions in silico. Binding affinities for 58 NLR-effector complexes ranged between -8.5 and -10.6 log(K), and binding energies between -11.8 and -14.4 kcal/mol-1, depending on the Area-Affinity model used. For 2427 "forced" NLR-effector complexes, these estimates showed larger variability, enabling identification of novel NLR-effector interactions with 99% accuracy using an Ensemble machine learning model. The narrow range of binding energies- and affinities for "true" interactions suggest a specific change in Gibbs free energy, and thus conformational change, is required for NLR activation. This is the first study to provide a method for predicting NLR-effector interactions, applicable to all pathosystems. Finally, the NLR-Effector Interaction Classification (NEIC) resource can streamline research efforts by identifying NLRs important for plant-pathogen resistance, advancing our understanding of plant immunity.

A fungal pathogen suppresses host leaf senescence to increase infection

Phytopathogens such as Puccinia striiformis f. sp. tritici (Pst) induce pigment retention at pathogen infection sites. Although pigment retention is commonly observed in diverse pathosystems, its underlying physiological mechanism remains largely unclear. Herein, we identify and characterize a wheat leaf senescence gene, TaSGR1, which enhances resistance against Pst by promoting leaf senescence and H2O2 accumulation while inhibiting photosynthesis. Knockout of TaSGR1 (STAYGREEN) in wheat increases pigment retention and plant susceptibility. Pst_TTP1 (TaTrx-Targeting Protein 1), a secreted rust fungal effector critical for Pst virulence, binds to the plastidial thioredoxin TaTrx (Thioredoxin), preventing its translocation into chloroplasts. Within the chloroplasts, TaTrx catalyzes the transformation of TaSGR1 oligomers into monomers. These TaSGR1 monomers accumulate in the chloroplasts, accelerating leaf senescence, H2O2 accumulation, and cell death. The inhibition of this oligomer-to-monomer transformation, caused by the failure of TaTrx to enter the chloroplast due to Pst_TTP1, impairs plant resistance against Pst. Overall, our study reveals the suppression of redox signaling cascade that catalyzes the transformation of TaSGR1 oligomers into monomers within chloroplasts and the inhibition of leaf chlorosis by rust effectors as key mechanisms underlying disease susceptibility.

Chromosome-level haplotype-resolved genome assembly of bread wheat's wild relative Aegilops mutica

Bread wheat (Triticum aestivum) is a vital staple crop, with an urgent need for increased production to help feed the world's growing population. Aegilops mutica (2n = 2x = 14; T genome) is a diploid wild relative of wheat carrying valuable agronomic traits resulting in its extensive exploitation for wheat improvement. This paper reports a chromosome-scale, haplotype-resolved genome assembly of Ae. mutica using HiFi reads and Omni-C data. The final lengths for the curated genomes were ~4.65 Gb (haplotype 1) and 4.56 Gb (haplotype 2), featuring a contig N50 of ~4.35 Mb and ~4.60 Mb, respectively. Genome annotation predicted 96,723 gene models and repeats. In summary, the genome assembly of Ae. mutica provides a valuable resource for the wheat breeding community, facilitating faster and more efficient pre-breeding of wheat to enhance food security.

Ferroptosis in plant immunity

Plant cell death is mediated by calcium, iron, and reactive oxygen species (ROS) signaling in plant immunity. The reconstruction of a nucleotide-binding leucine-rich-repeat receptor (NLR) supramolecular structure, called the resistosome, is intimately involved in the hypersensitive response (HR), a type of cell death involved in effector-triggered immunity (ETI). Iron is a crucial redox catalyst in various cellular reactions. Ferroptosis is a regulated, non-apoptotic form of iron- and ROS-dependent cell death in plants. Pathogen infections trigger iron accumulation and ROS bursts in plant cells, leading to lipid peroxidation via the Fenton reaction and subsequent ferroptosis in plant cells similar to that in mammalian cells. The small-molecule inducer erastin triggers iron-dependent lipid ROS accumulation and glutathione depletion, leading to HR cell death in plant immunity. Calcium (Ca2+) is another major mediator of plant immunity. Cytoplasmic Ca2+ influx through calcium-permeable channels, the resistosomes, mediates iron- and ROS-dependent ferroptotic cell death under reduced glutathione reductase (GR) expression levels in the ETI response. Acibenzolar-S-methyl (ASM), a plant defense activator, enhances Ca2+ influx, ROS and iron accumulation, and lipid peroxidation to trigger ferroptotic cell death. These breakthroughs suggest a potential role for Ca2+ signaling in ferroptosis and its coordination with iron and ROS signaling in plant immunity. In this review, we highlight the essential roles of calcium, iron, and ROS signaling in ferroptosis during plant immunity and discuss advances in the understanding of how Ca2+-mediated ferroptotic cell death orchestrates effective plant immune responses against invading pathogens.

Fine mapping of stripe rust resistance gene YrAn1589 in common wheat using Wheat660K SNP array and BSR-Seq

KEY MESSAGE

A new stripe rust resistance gene YrAn1589 in Chinese wheat Annong1589 was mapped to a 160.9-166.6 kb interval on chromosome arm 3BL and co-segregated with a marker CAPS9 developed from candidate gene TraesCS3B03G1054600.  Stripe rust, caused by Puccinia. striiformis f. sp. tritici (Pst), is a devastating fungal disease that can significantly reduce wheat yield. The Chinese wheat cultivar Annong1589 demonstrates high resistance against the predominant Pst races in the Huang-Huai valley wheat region. The present study aimed to identify the stripe rust resistance gene in Annong1589. Genetic analysis indicated that the resistance in Annong1589 was conferred by a single dominant gene, provisionally designated YrAn1589. Using Wheat660K SNP array, bulked segregant RNA sequencing and new molecular markers developed, the resistance gene was mapped to a 160.9-166.6 kb region between CAPS8 and CAPS10 on chromosome 3BL based on IWGSC CS RefSeq v2.1 and eight other reference genome sequences, including eight high-confidence annotated genes. Transcriptome and qRT-PCR analyses revealed significantly upregulated expression of TraesCS3B03G1054600 in resistant plants following CYR32 inoculation, suggesting it is a potential candidate gene for YrAn1589. A functional marker CAPS9 developed from a A/G polymorphic SNP in the candidate co-segregated with YrAn1589 in the F2 population. Subcellular localization experiments showed that TraesCS3B03G1054600 protein was localized in the cytoplasm and nucleus, implying its role in immune response and resistance. Our findings establish YrAn1589 as a new stripe rust resistance gene, providing valuable gene resource and molecular markers for improvement of stripe rust resistance in wheat.

Salicylic acid: The roles in plant immunity and crosstalk with other hormones

Land plants use diverse hormones to coordinate their growth, development and responses against biotic and abiotic stresses. Salicylic acid (SA) is an essential hormone in plant immunity, with its levels and signaling tightly regulated to ensure a balanced immune output. Over the past three decades, molecular genetic analyses performed primarily in Arabidopsis have elucidated the biosynthesis and signal transduction pathways of key plant hormones, including abscisic acid, jasmonic acid, ethylene, auxin, cytokinin, brassinosteroids, and gibberellin. Crosstalk between different hormones has become a major focus in plant biology with the goal of obtaining a full picture of the plant hormone signaling network. This review highlights the roles of SA in plant immunity and summarizes our current understanding of the pairwise interactions of SA with other major plant hormones. The complexity of these interactions is discussed, with the hope of stimulating research to address existing knowledge gaps in hormone crosstalk, particularly in the context of balancing plant growth and defense.

NLR-mediated antiviral immunity in plants

Plant viruses cause substantial agricultural devastation and economic losses worldwide. Plant nucleotide-binding domain leucine-rich repeat receptors (NLRs) play a pivotal role in detecting viral infection and activating robust immune responses. Recent advances, including the elucidation of the interaction mechanisms between NLRs and pathogen effectors, the discovery of helper NLRs, and the resolution of the ZAR1 resistosome structure, have significantly deepened our understanding of NLR-mediated immune responses, marking a new era in NLR research. In this scenario, significant progress has been made in the study of NLR-mediated antiviral immunity. This review comprehensively summarizes the progress made in plant antiviral NLR research over the past decades, with a focus on NLR recognition of viral pathogen effectors, NLR activation and regulation, downstream immune signaling, and the engineering of NLRs.

A cell wall-associated kinase phosphorylates NLR immune receptor to negatively regulate resistosome formation

Plants deploy intracellular nucleotide-binding leucine-rich repeats (NLRs) to detect pathogen effectors and initiate immune responses. Although the activation mechanism of some plant NLRs forming resistosomes has been elucidated, whether NLR resistosome assembly is regulated to fine-tune immunity remains enigmatic. Here we used an antiviral coiled coil-nucleotide-binding site-leucine rich repeat, Barley Stripe Resistance 1 (BSR1), as a model and demonstrate that BSR1 is phosphorylated. Using a proximity labelling approach, we identified a wall-associated kinase-like protein 20 (WAKL20) which negatively regulates BSR1-mediated immune responses by directly phosphorylating the Ser470 residue in the NB-ARC domain of BSR1. Mechanistically, Ser470 phosphorylation results in a steric clash of intramolecular domains of BSR1, thereby compromising BSR1 oligomerization. The phosphorylation site is conserved among multiple plant NLRs and our results show that WAKL20 participates in other NLR-mediated immune responses besides BSR1. Together, our data reveal phosphorylation as a mechanism for modulating plant resistosome assembly, and provide new insight into NLR-mediated plant immunity.

TaANK-TPR1 enhances wheat resistance against stripe rust via controlling gene expression and protein activity of NLR protein TaRPP13L1

Nucleotide-binding site, leucine-rich repeat (NLR) proteins activate a robust immune response on recognition of pathogen invasion. However, the function and regulatory mechanisms of NLRs during Puccinia striiformis f. sp. tritici (Pst) infection in wheat remain elusive. Here, we identify an ankyrin (ANK) repeat and tetratricopeptide repeat (TPR)-containing protein, TaANK-TPR1, which plays a positive role in the regulation of wheat resistance against Pst and the immune response of NLR. TaANK-TPR1 targets the NLR protein TaRPP13L1 (Recognition of PeronosporaParasitica 13-like 1) to facilitate its homodimerization and cell death to enhance the resistance of wheat against Pst. Meanwhile, TaANK-TPR1 binds to the TGACGT motif (methyl jasmonate-responsive element) of the TaRPP13L1 promoter and activates TaRPP13L1 transcription. Both TaANK-TPR1 and TaRPP13L1 respond to jasmonic acid (JA) signaling via the TGACGT element. Importantly, overexpressing TaRPP13L1 confers robust rust resistance without impacting important agronomic traits in the field. These findings identify a regulatory mechanism of NLR protein and provide targets for improving crop disease resistance.

Genome-Wide In Silico Analysis of Leucine-Rich Repeat R-Genes in Perilla citriodora: Classification and Expression Insights

BACKGROUND

Resistance (R) genes are crucial for defending Perilla against pathogens like anthracnose, downy mildew, and phytophthora blight. Nucleotide-binding site leucine-rich repeat (NBS-LRR) genes, the largest R-gene family, play a central role in immunity. This study aimed to identify and characterize NBS-LRR genes in P. citriodora 'Jeju17'.

METHODS

Previously conducted genome-wide data for 'Jeju17' were analyzed in silico to identify NBS-LRR genes.

RESULTS

A total of 535 NBS-LRR genes were identified, with clusters on chromosomes 2, 4, and 10. A unique RPW8-type R-gene was located on chromosome 7.

CONCLUSIONS

This study provides insights into the NBS-LRR gene family in 'Je-ju17', highlighting its role in disease resistance and evolutionary dynamics. By identifying can-didate R-genes, this research supports breeding programs to develop disease-resistant cultivars and improves our understanding of plant immunity.

Genome-wide association study reveals major loci for resistance to septoria tritici blotch in a Tunisian durum wheat collection

Septoria tritici blotch (STB) is a devastating fungal disease affecting durum and bread wheat worldwide. Tunisian durum wheat landraces are reported to be valuable genetic resources for resistance to STB and should prominently be deployed in breeding programs to develop new varieties resistant to STB disease. In this study, a collection of 367 old durum and 6 modern wheat genotypes previously assessed using single Tunisian Zymoseptoria tritici isolate TUN06 during 2016 and 2017 and TM220 isolate during 2017 were phenotyped for resistance to a mixture of isolates (BULK) under field conditions. Significant correlations for disease traits using the three different inoculums were observed. Using 7638 SNP markers, fifty-one marker-trait associations (MTAs) for STB resistance were identified by genome-wide association study (GWAS) at Bonferroni correction threshold of -log10(P) > 5.184 with phenotypic variance explained (PVE) reaching up to 58%. A total of eleven QTL were identified using TUN06 isolate mean disease scoring (TUNMeanD and TUNMeanA) including threeQTL controlling resistance to both isolates TUN06 and TM220. A major QTL was identified on each of chromosomes 1B, 4B, 5A, and 7B, respectively. The QTL on 7B chromosome colocalized with Stb8 identified in bread wheat. Four QTL including the major QTL identified on chromosome 1B were considered as novel. SNP linked to the significant QTL have the potential to be used in marker-assisted selection for breeding for resistance to STB.

The role of Exo70s in plant defense against pathogens and insect pests and their application for crop breeding

Plant diseases caused by pathogens and pests lead to crop losses, posing a threat to global food security. The secretory pathway is an integral component of plant defense. The exocyst complex regulates the final step of the secretory pathway and is thus essential for secretory defense. In the last decades, several subunits of the exocyst complex have been reported to be involved in plant defense, especially Exo70s. This comprehensive review focuses on the functions of the exocyst Exo70s in plant immunity, particularly in recognizing pathogen and pest signatures. We discussed Exo70's interactions with immune receptors and other immune-related proteins, its symbiotic relationships with microbes, and its role in non-host resistance. Finally, we discussed the future engineering breeding of crops with resistance to pathogens and pests based on our current understanding of Exo70s.

Convergent reduction of immune receptor repertoires during plant adaptation to diverse special lifestyles and habitats

Plants deploy cell-surface pattern recognition receptors (PRRs) and intracellular nucleotide-binding site-leucine-rich repeat receptors (NLRs) to recognize pathogens. However, how plant immune receptor repertoires evolve in responding to changed pathogen burdens remains elusive. Here we reveal the convergent reduction of NLR repertoires in plants with diverse special lifestyles/habitats (SLHs) encountering low pathogen burdens. Furthermore, a parallel but milder reduction of PRR genes in SLH species was observed. The reduction of PRR and NLR genes was attributed to both increased gene loss and decreased gene duplication. Notably, pronounced loss of immune receptors was associated with the complete absence of signalling components from the enhanced disease susceptibility 1 (EDS1) and the resistance to powdery mildew 8 (RPW8)-NLR (RNL) families. In addition, evolutionary pattern analysis suggested that the conserved toll/interleukin-1 receptor (TIR)-only proteins might function tightly with EDS1/RNL. Taken together, these results reveal the hierarchically adaptive evolution of the two-tiered immune receptor repertoires during plant adaptation to diverse SLHs.

Genome-Wide Association Study of Bacterial Blight Resistance in Soybean

Bacterial blight caused by Pseudomonas syringae pv. glycinea (Psg) is a widespread foliar disease. Although four Resistance to Pseudomonas syringae pv. glycinea (Rpg) 1 to 4 (Rpg1∼4) genes that have been observed to segregate in a Mendelian pattern have been reported to confer resistance to Psg in soybean, the genetic basis of quantitative resistance to bacterial blight in soybean remains unclear. In the present study, the Psg resistance of two soybean association panels consisting of 573 and 213 lines, respectively, was phenotyped in multiple environments in 2014 to 2016. Genome-wide association study was performed using two models, FarmCPU and BLINK, to identify Psg resistance loci. A total of 40 soybean varieties with high level of Psg resistance were identified, and 14 quantitative trait loci (QTLs) were detected on 12 soybean chromosomes. These QTLs were identified for the first time. The majority of the QTLs were detected only in one or the other association panels, while qRPG-18-1 was detected in both association panels for at least one growing season. A total of 46 candidate Psg resistance genes were identified from the qRpg_13_1, qRPG-15-1, and qRPG-18-1 loci based on gene function annotation. In addition, we found the genomic region covering rpg1-b and rpg1-r harbored the synteny with a genomic region on chromosome 15 and identified 16 nucleotide binding site-leucine-rich repeat (NBS-LRR) genes as the candidate Psg resistance genes from the synteny blocks. This study provides new information for dissecting the genetic control of Psg resistance in soybean.

Sorbitol induces flavonoid accumulation as a secondary signal via the nanoencapsulated SPc/lncRNA809-MmNAC17 module against Alternaria alternata in Malus micromalus

Sorbitol is an important primary metabolite that serves as both a carbon source and signal to pathogens. The leaf diseases caused by Alternata alternata are particularly serious in crabapple (Malus micromalus). Here, we found that sorbitol can enhance the resistance of crabapple to A. alternata R1 by increasing the content of flavonoid catechin. Nanomaterials as an emerging technology tool can efficiently deliver lncRNA to target cells. Here, we found nanoencapsulated lncRNA809 (SPc/lncRNA809) exhibits significant resistance to R1strain. To elucidate the effect of SPc/lncRNA809 on flavonoids catechin synthesis, we observed the expression of lncRNA809 was consistent with that of MmNAC17 which regulates the synthesis of catechin and both could jointly respond to sorbitol. MmNAC17 induced the accumulation of catechin in vivo by directly activating the expression of catechin synthase genes MmF3H and MmLAR. Correspondingly, overexpression of lncRNA809 significantly upregulated the expression of MmNAC17 and enhanced the disease resistance. This study reveals for the first time that sorbitol positively regulates the expression of MmNAC17 through lncRNA809, promoting the accumulation of catechin via the expression of MmF3H and MmLAR, ultimately improving the defense response of M. micromalus. This research provides a crucial foundation for the establishment and application of sorbitol-based signaling regulatory networks.

Resistify: A Novel NLR Classifier That Reveals Helitron-Associated NLR Expansion in Solanaceae

Nucleotide-binding domain leucine-rich repeat (NLR) proteins are a key component of the plant innate immune system. In plant genomes, NLRs exhibit considerable presence/absence variation and sequence diversity. Recent advances in sequencing technologies have made the generation of high-quality novel plant genome assemblies considerably more straightforward. Accurately identifying NLRs from these genomes is a prerequisite for improving our understanding of NLRs and identifying novel sources of disease resistance. While several tools have been developed to predict NLRs, they are hampered by low accuracy, speed, and availability. Here, the NLR annotation tool Resistify is presented. Resistify is an easy-to-use, rapid, and accurate tool to identify and classify NLRs from protein sequences. Applying Resistify to the RefPlantNLR database demonstrates that it can correctly identify NLRs from a diverse range of species. Applying Resistify in combination with tools to identify transposable elements to a panel of Solanaceae genomes reveals a previously undescribed association between NLRs and Helitron transposable elements.

The Roles of MicroRNAs in the Regulation of Rice-Pathogen Interactions

Rice is exposed to attacks by the three most destructive pathogens, Magnaporthe oryzae (M. oryzae), Xanthomonas oryzae pv. oryzae (Xoo), and Rhizoctonia solani (R. solani), which cause substantial yield losses and severely threaten food security. To cope with pathogenic infections, rice has evolved diverse molecular mechanisms to respond to a wide range of pathogens. Among these strategies, plant microRNAs (miRNAs), endogenous single-stranded short non-coding RNA molecules, have emerged as promising candidates in coordinating plant-pathogen interactions. MiRNAs can modulate target gene expression at the post-transcriptional level through mRNA cleavage and/or translational inhibition. In rare instances, they also influence gene expression at the transcriptional level through DNA methylation. In recent years, substantial advancements have been achieved in the investigation of microRNA-mediated molecular mechanisms in rice immunity. Therefore, we attempt to summarize the current advances of immune signaling mechanisms in rice-pathogen interactions that are regulated by osa-miRNAs, including their functions and molecular mechanisms. We also focus on recent findings concerning the role of osa-miRNAs that respond to M. oryzae, Xoo, and R. solani, respectively. These insights enhance our understanding of how the mechanisms of osa-miRNAs mediate rice immunity and may facilitate the development of improved strategies for breeding pathogen-resistant rice varieties.

Transposon-triggered epigenetic chromatin dynamics modulate EFR-related pathogen response

Infectious diseases drive wild plant evolution and impact crop yield. Plants, like animals, sense biotic threats through pattern recognition receptors (PRRs). Overly robust immune responses can harm plants; thus, understanding the tuning of defense response mechanisms is crucial for developing pathogen-resistant crops. In this study, we found that an inverted-repeat transposon (EFR-associated IR, Ea-IR) located between the loci encoding PRRs ELONGATION FACTOR-TU RECEPTOR (EFR) and myosin XI-k (XI-k) in Arabidopsis affects chromatin organization, promoting the formation of a repressive chromatin loop. Upon pathogen infection, chromatin changes around EFR and XI-k correlate with increased EFR transcription. Pathogen-induced chromatin opening causes RNA polymerase II readthrough, producing a longer, Ea-IR-containing XI-k transcript, processed by Dicer-like enzymes into small RNAs, which reset chromatin to a repressive state attenuating the immune response after infection. Arabidopsis accessions lacking Ea-IR have higher basal EFR levels and resistance to pathogens. We show a scenario in which a transposon, chromatin organization and gene expression interact to fine-tune immune responses, during both the course of infection and the course of evolution.

A bacterial type III effector hijacks plant ubiquitin proteases to evade degradation

Gram-negative bacterial pathogens inject effector proteins inside plant cells using a type III secretion system. These effectors manipulate plant cellular functions and suppress the plant immune system in order to promote bacterial proliferation. Despite the fact that bacterial effectors are exogenous threatening proteins potentially exposed to the protein degradation systems inside plant cells, effectors are relative stable and able to perform their virulence functions. In this work, we found that RipE1, an effector protein secreted by the bacterial wilt pathogen, Ralstonia solanacearum, undergoes phosphorylation of specific residues inside plant cells, and this promotes its stability. Moreover, RipE1 associates with plant ubiquitin proteases, which contribute to RipE1 deubiquitination and stabilization. The absence of those specific phosphorylation sites or specific host ubiquitin proteases leads to a substantial decrease in RipE1 protein accumulation, indicating that RipE1 hijacks plant post-translational modification regulators in order to promote its own stability. These results suggest that effector stability or degradation in plant cells constitute another molecular event subject to co-evolution between plants and pathogens.

Deciphering the landscape and evolutionary trajectory of NLR immune receptors in Dioscorea alata

Dioscorea alata, a key tuber crop for global food security, is threatened by anthracnose disease caused by Colletotrichum gloeosporioides. However, identification of functional resistance genes against C. gloeosporioides in D. alata is challenging due to low flowering and hybridization efficiency of this plant. Nucleotide-binding leucine-rich repeat (NLR) genes constitute the largest group of plant disease resistance genes, from which functional genes against diverse pathogens across various crops have been cloned. In this study, a comprehensive genome-wide analysis identified 346 NLR genes from D. alata, including one RNL and 345 CNLs. These NLRs were unequally distributed on 20 chromosomes, with chromosome 3 harboring the highest number (78 NLR genes). The majority of NLR genes (91%) were located in multigene clusters, implying that tandem or proximal duplication was the primary driving force for NLR gene expansion in D. alata. Comparative analysis of Dioscoreaceae species revealed high variability and differential expansion patterns of NLR genes. In addition, transcriptome profiling of D. alata post-infection with C. gloeosporioides identified 12 differentially expressed NLR genes. In summary, this study sheds new light on the genetic architecture and evolutionary dynamics of D. alata NLR genes, offering valuable insights for cloning functional genes against C. gloeosporioides.

Salicylic Acid-Induced Expression Profiles of LRR and LRR-RLK Candidate Genes Modulate Mungbean Yellow Mosaic India Virus Resistance in Blackgram and Its Two Wild Non-Progenitors

Blackgram is an important short-duration grain legume, but its yield is highly affected by various stresses. Among biotic stresses, yellow mosaic disease (YMD) is known as a devastating disease that leads to 100% yield loss under severe conditions. The cultivated lines possess resistance, but exploring more diverse sources of resistance may be useful for pyramiding to improve the durability of said resistance. Some wild Vigna species have potentially demonstrated a high level of resistance. R-genes, including gene families of leucine-rich repeats (LRRs) and leucine-rich repeat receptor-like kinases (LRR-RLKs), are known for modulating the resistance in plants against various biotic stresses. The first comprehensive analysis of the LRR and LRR-RLK gene families in mungbean is reported in the present study. A total of forty-six candidate genes were identified and grouped into eight clades. Protein motif analysis showed that the "Pkinase domain" and "LRR domains" were conserved in most of the R-proteins. The expression of candidate genes viz. VrNBS_TNLRR-8, VrLRR_RLK-20, VrLRR_RLK-17, and VrLRR_RLK-19 demonstrated significantly up-regulated expression upon YMD infection in control and salicylic acid-primed (SA-primed) plants. The analysis provides insight into the diversity and robust candidate genes for functional studies modulating YMD resistance altered by salicylic acid.

k-mer genome-wide association study for anthracnose and BCMV resistance in a Phaseolus vulgaris Andean Diversity Panel

Access to broad genomic resources and closely linked marker-trait associations for common beans (Phaseolus vulgaris L.) can facilitate development of improved varieties with increased yield, improved market quality traits, and enhanced disease resistance. The emergence of virulent races of anthracnose (caused by Colletotrichum lindemuthianum) and bean common mosaic virus (BCMV) highlight the need for improved methods to identify and incorporate pan-genomic variation in breeding for disease resistance. We sequenced the P. vulgaris Andean Diversity Panel (ADP) and performed a genome-wide association study (GWAS) to identify associations for resistance to BCMV and eight races of anthracnose. Historical single nucleotide polymorphism (SNP)-chip and phenotypic data enabled a three-way comparison between SNP-chip, reference-based whole genome shotgun sequence (WGS)-SNP, and reference-free k-mer (short nucleotide subsequence) GWAS. Across all traits, there was excellent concordance between SNP-chip, WGS-SNP, and k-mer GWAS results-albeit at a much higher marker resolution for the WGS data sets. Significant k-mer haplotype variation revealed selection of the linked I-gene and Co-u traits in North American breeding lines and cultivars. Due to structural variation, only 9.1 to 47.3% of the significantly associated k-mers could be mapped to the reference genome. Thus, to determine the genetic context of cis-associated k-mers, we generated draft whole genome assemblies of four ADP accessions and identified an expanded local repertoire of disease resistance genes associated with resistance to anthracnose and BCMV. With access to variant data in the context of a pan-genome, high resolution mapping of agronomic traits for common bean is now feasible.

The pan-NLRome analysis based on 23 genomes reveals the diversity of NLRs in Brassica napus

Brassica napus, a globally significant oilseed crop, exhibits a wide distribution across diverse climatic zones. B. napus is being increasingly susceptible to distinct diseases, such as blackleg, clubroot and sclerotinia stem rot, leading to substantial reductions in yield. Nucleotide-binding site leucine-rich repeat genes (NLRs), the most pivotal family of resistance genes, can be effectively harnessed by identifying and uncovering their diversity to acquire premium disease-resistant gene resources. Here, we collected the genomes of 23 accessions and established the first comprehensive pan-NLRome in B. napus by leveraging multiple genomic resources. We observe significant variation in the number of NLR genes across different B. napus accessions, ranging from 189 to 474. Notably, TNL (TIR-NBS-LRR) genes constitute approximately half of the total count, indicating their predominant presence in B. napus. The number of NLRs in the C subgenome is significantly higher than that in the A subgenome, and chromosome C09 exhibits the highest density of NLR genes with featuring multiple NLR clusters. Domain analysis reveals that the integrated domains significantly enhance the diversity of NLRs, with B3 DNA binding, VQ, and zinc fingers being the most prevalent integrated domains. Pan-genomic analysis reveals that the core type of NLR genes, which is present in most accessions, constitutes approximately 58% of the total NLRs. Furthermore, we conduct a comparative analysis of the diversity of NLR genes across distinct ecotypes, leading to the identification of ecotype-specific NLRs and their integrated domains. In conclusion, our study effectively addresses the limitations of a single reference genome and provides valuable insights into the diversity of NLR genes in B. napus, thereby contributing to disease resistance breeding.

Paraburkholderia tropica Primes a Multilayered Transcriptional Defense Response to the Nematode Meloidogyne spp. in Tomato

Meloidogyne causes a devastating disease known as root-knot that affects tomatoes and other cash crops worldwide. Conversely, Paraburkholderia tropica has proven beneficial in mitigating the effects of various pathogens in plants. We aimed to unravel the molecular events that underlie the beneficial effects of the bacterium and the detrimental impacts of the nematode when inoculated separately or together in tomato plants. The transcriptional responses induced by P. tropica (TB group (tomato-bacteria group)), Meloidogyne spp. (TN group (tomato-nematode group)) or by the two agents (TBN group (tomato-bacteria-nematode group)) in tomato were assessed by RNA-seq. We implemented a transcript discovery pipeline which allowed the identification of 2283 putative novel transcripts. Differential expression analysis revealed that upregulated transcripts were much more numerous than downregulated ones. At the gene ontology level, the most activated term was 'hydrolase activity acting on ester bonds' in all groups. In addition, when both microbes were inoculated together, 'hydrolase activity acting on O-glycosyl compounds' was activated. This finding suggests defense responses related to lipid and carbohydrate metabolism, membrane remodeling and signal transduction. Notably, defense genes, transcription factors and protein kinases stood out. Differentially expressed transcripts suggest the activation of a multifaceted plant defense response against the nematode occurred, which was exacerbated by pre-inoculation of P. tropica.

Re-localization of a repeat-containing fungal effector by apoplastic protein Chitinase-like 1 blocks its toxicity

A fungal effector that is toxic to plant cells was identified in Verticillium dahliae. The effector contains a non-canonical Common in several Fungal Extracellular Membrane proteins (CFEM) domain, a tandem repeat region consisting of four 14-amino acid repeats rich in proline, and a C-terminal region, thus is designated V. dahliae tetrapeptide repeat protein (VdTRP). The membrane targeting of VdTRP is vital for its cell toxicity. CFEM mediates the membrane targeting and the tandem repeat region exerts the toxic function upon cell membrane. The chitinase-like 1 (CTL1), an essential apoplastic protein of cotton, can redirect VdTRP from cell membrane to apoplast. Transgenic cotton overexpressing CTL1 greatly enhances cotton resistance to V. dahliae without affecting cotton growth and development, implicating its potential application in breeding cotton with high wilt resistance. Our data demonstrates that genetic manipulation of effector target constitutes potential strategy for improving crop resistance to fungal pathogens.

Applications of CRISPR Technologies in Forestry and Molecular Wood Biotechnology

Forests worldwide are under increasing pressure from climate change and emerging diseases, threatening their vital ecological and economic roles. Traditional breeding approaches, while valuable, are inherently slow and limited by the long generation times and existing genetic variation of trees. CRISPR technologies offer a transformative solution, enabling precise and efficient genome editing to accelerate the development of climate-resilient and productive forests. This review provides a comprehensive overview of CRISPR applications in forestry, exploring its potential for enhancing disease resistance, improving abiotic stress tolerance, modifying wood properties, and accelerating growth. We discuss the mechanisms and applications of various CRISPR systems, including base editing, prime editing, and multiplexing strategies. Additionally, we highlight recent advances in overcoming key challenges such as reagent delivery and plant regeneration, which are crucial for successful implementation of CRISPR in trees. We also delve into the potential and ethical considerations of using CRISPR gene drive for population-level genetic alterations, as well as the importance of genetic containment strategies for mitigating risks. This review emphasizes the need for continued research, technological advancements, extensive long-term field trials, public engagement, and responsible innovation to fully harness the power of CRISPR for shaping a sustainable future for forests.

Use of the Puccinia sorghi haustorial transcriptome to identify and characterize AvrRp1-D recognized by the maize Rp1-D resistance protein

The common rust disease of maize is caused by the obligate biotrophic fungus Puccinia sorghi. The maize Rp1-D allele imparts resistance against the P. sorghi IN2 isolate by initiating a defense response that includes a rapid localized programmed cell death process, the hypersensitive response (HR). In this study, to identify AvrRp1-D from P. sorghi IN2, we employed the isolation of haustoria, facilitated by a biotin-streptavidin interaction, as a powerful approach. This method proves particularly advantageous in cases where the genome information for the fungal pathogen is unavailable, enhancing our ability to explore and understand the molecular interactions between maize and P. sorghi. The haustorial transcriptome generated through this technique, in combination with bioinformatic analyses such as SignalP and TMHMM, enabled the identification of 251 candidate effectors. We ultimately identified two closely related genes, AvrRp1-D.1 and AvrRp1-D.2, which triggered an Rp1-D-dependent defense response in Nicotiana benthamiana. AvrRp1-D-induced Rp1-D-dependent HR was further confirmed in maize protoplasts. We demonstrated that AvrRp1-D.1 interacts directly and specifically with the leucine-rich repeat (LRR) domain of Rp1-D through yeast two-hybrid assay. We also provide evidence that, in the absence of Rp1-D, AvrRp1-D.1 plays a role in suppressing the plant immune response. Our research provides valuable insights into the molecular interactions driving resistance against common rust in maize.

Intra species dissection of phytophthora capsici resistance in black pepper

INTRODUCTION

Black pepper, a financially significant tropical crop, assumes a pivotal role in global agriculture for the major source of specie flavor. Nonetheless, the growth and productivity of black pepper face severe impediments due to the destructive pathogen Phytophthora capsici, ultimately resulting in black pepper blight. The dissecting for the genetic source of pathogen resistance for black pepper is beneficial for its global production. The genetic sources include the variations on gene coding sequences, transcription capabilities and epigenetic modifications, which exerts hierarchy of influences on plant defense against pathogen. However, the understanding of genetic source of disease resistance in black pepper remains limited.

METHODS

The wild species Piper flaviflorum (P. flaviflorum, Pf) is known for blight resistance, while the cultivated species P. nigrum is susceptible. To dissecting the genetic sources of pathogen resistance for black pepper, the chromatin modification on H3K4me3 and transcriptome of black pepper species were profiled for genome wide comparative studies, applied with CUT&Tag and RNA sequencing technologies.

RESULTS

The intraspecies difference between P. flaviflorum and P. nigrum on gene body region led to coding variations on 5137 genes, including 359 gene with biotic stress responses and regulation. P. flaviflorum exhibited a more comprehensive resistance response to Phytophthora capsici in terms of transcriptome features. The pathogen responsive transcribing was significant associated with histone modification mark of H3K4me3 in black pepper. The collective data on variations of sequence, transcription activity and chromatin structure lead to an exclusive jasmonic acid-responsive pathway for disease resistance in P. flaviflorum was revealed. This research provides a comprehensive frame work to identify the fine genetic source for pathogen resistance from wild species of black pepper.

Genome-wide characterization of nitric oxide-induced NBS-LRR genes from Arabidopsis thaliana and their association in monocots and dicots

BACKGROUND

Nitric oxide (NO) is pivotal in regulating the activity of NBS-LRR specific R genes, crucial components of the plant's immune system. It is noteworthy that previous research has not included a genome-wide analysis of NO-responsive NBS-LRR genes in plants.

RESULTS

The current study examined 29 NO-induced NBS-LRR genes from Arabidopsis thaliana, along with two monocots (rice and maize) and two dicots (soybean and tomato) using genome-wide analysis tools. These NBS-LRR genes were subjected to comprehensive characterization, including analysis of their physio-chemical properties, phylogenetic relationships, domain and motif identification, exon/intron structures, cis-elements, protein-protein interactions, prediction of S-Nitrosylation sites, and comparison of transcriptomic and qRT-PCR data. Results showed the diverse distribution of NBS-LRR genes across chromosomes, and variations in amino acid number, exons/introns, molecular weight, and theoretical isoelectric point, and they were found in various cellular locations like the plasma membrane, cytoplasm, and nucleus. These genes predominantly harbor the NB-ARC superfamily, LRR, LRR_8, and TIR domains, as also confirmed by motif analysis. Additionally, they feature species-specific PLN00113 superfamily and RX-CC_like domain in dicots and monocots, respectively, both responsive to defense against pathogen attacks. The NO-induced NBS-LRR genes of Arabidopsis reveal the presence of cis-elements responsive to phytohormones, light, stress, and growth, suggesting a wide range of responses mediated by NO. Protein-protein interactions, coupled with the prediction of S-Nitrosylation sites, offer valuable insights into the regulatory role of NO at the protein level within each respective species.

CONCLUSION

These above findings aimed to provide a thorough understanding of the impact of NO on NBS-LRR genes and their relationships with key plant species.

Bioinformatics and functional analysis of EDS1 genes in Brassica napus in response to Plasmodiophora brassicae infection

Enhanced Disease Susceptibility 1 (EDS1) is a key regulator of plant-pathogen-associated molecular pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) responses. In the Brassica napus genome, we identified six novel EDS1 genes, among which four were responsive to clubroot infection, a major rapeseed disease resistant to chemical control. Developing resistant cultivars is a potent and economically viable strategy to control clubroot infection. Bioinformatics analysis revealed conserved domains and structural uniformity in Bna-EDS1 homologs. Bna-EDS1 promoters harbored elements associated with diverse phytohormones and stress responses, highlighting their crucial roles in plant defense. A functional analysis was performed with Bna-EDS1 overexpression and RNAi transgenic lines. Bna-EDS1 overexpression boosted resistance to clubroot and upregulated defense-associated genes (PR1, PR2, ICS1, and CBP60), while Bna-EDS1 RNAi increased plant susceptibility, indicating suppression of the defense signaling pathway downstream of NBS-LRRs. RNA-Seq analysis identified key transcripts associated with clubroot resistance, including phenylpropanoid biosynthesis. Activation of SA regulator NPR1, defense signaling markers PR1 and PR2, and upregulation of MYC-TFs suggested that EDS1-mediated clubroot resistance potentially involves the SA pathway. Our findings underscore the pivotal role of Bna-EDS1-dependent mechanisms in resistance of B. napus to clubroot disease, and provide valuable insights for fortifying resistance against Plasmodiophora brassicae infection in rapeseed.

Transcriptional regulation of hormone signalling genes in black pepper in response to Phytophthora capsici

INTRODUCTION

Black pepper (Piper nigrum L.) is a non-model spice crop of significant agricultural and biological importance. The 'quick wilt' disease caused by the oomycete Phytophthora capsici is a major threat, leading to substantial crop loss. The molecular mechanisms governing the plant immune responses to this pathogen remain unclear. This study employs RNA sequencing and transcriptome analysis to explore the defense mechanisms of P. nigrum against P. capsici.

RESULTS

Two-month-old P. nigrum plantlets were subjected to infection with P. capsici, and leaf samples were collected at 6- and 12-hours post-inoculation. RNA was extracted, sequenced, and the resulting data were processed and assembled. Differential gene expression analysis was conducted to identify genes responding to the infection. Additionally, the study investigated the involvement of Salicylic acid (SA), Jasmonic acid (JA), and Ethylene (ET) signalling pathways. Our transcriptome assembly comprised 64,667 transcripts with 96.7% completeness, providing valuable insights into the P. nigrum transcriptome. Annotation of these transcripts identified functional categories and domains, provided details on molecular processes. Gene expression analysis identified 4,714 transcripts at 6 h post-infection (hpi) and 9,416 at 12 hpi as differentially expressed, revealing dynamic regulation of immune-related genes. Furthermore, the study investigated key genes involved in biosynthesis pathways of Salicylic acid, Jasmonic acid, and Ethylene signalling. Notably, we found differential regulation of critical genes associated with these pathways while comparing data before and after infection, thereby shedding light on their roles in defense mechanism in P. nigrum defense.

CONCLUSIONS

This comprehensive transcriptome analysis of P. nigrum response to P. capsici attack provides valuable insights into the plant defense mechanisms. The dynamic regulation of innate immunity and the involvement of key signalling pathways highlight the complexity of the plant-pathogen interaction. This study contributes to our understanding of plant immunity and offers potential strategies for enhancing P. nigrum resistance to this harmful pathogen.

GWAS of resistance to three bacterial diseases in the Andean common bean diversity panel

Bacterial brown spot (BBS) caused by Pseudomonas syringae pv. syringae (Pss), common bacterial blight (CBB) caused by Xanthomonas axonopodis pv. phaseoli (Xap) and Xanthomonas fuscans subsp. fuscans (Xff), and halo bacterial blight (HBB), caused by Pseudomonas syringae pv. phaseolicola (Psph), are major bacterial diseases that severely affect common bean yields and global food security. Andean-origin dry beans, representing large-seeded market classes, are particularly susceptible. Using 140,325 SNPs, a multi-locus GWAS was conducted on subsets of the Andean diversity panel (ADP) phenotyped for BBS in South Africa, CBB in Puerto Rico, South Africa, and Zambia, and HBB in South Africa, through natural infection, artificial inoculation, or both. Twenty-four QTL associated with resistance were identified: nine for BBS, eight for CBB, and seven for HBB. Four QTL intervals on Pv01, Pv03, Pv05, and Pv08 overlapped with BBS and HBB resistance. A genomic interval on Pv01, near the fin gene, which determines growth habit, was linked to resistance to all three pathogens. Different QTLs were detected for BBS and CBB resistance when phenotyped under natural infection versus artificial inoculation. These results underscore the importance of combining phenotyping methods in multi-GWAS to capture the full genetic spectrum. Previously recognized CBB resistance QTL SAP6 and SU91 and HBB resistance QTL HB4.2, and HB5.1, were observed. Other common (MAF >0.25) and rare (MAF <0.05) resistance QTL were also detected. Overall, these findings enhance the understanding and utilization of bacterial resistance present in ADP for the development of common beans with improved resistance.

Variability and functional characterization of the Phakopsora pachyrhizi Egh16-like effectors

Effector proteins in Phakopsora pachyrhizi (Pp), the causative agent of Asian Soybean rust, are involved in the infection process. A previous study identified a rust effector Egh16-like family based expression profile during the interaction with soybean. Herein, we scrutinized available the Pp genomes to validate the predicted Egh16-like family of Pp and identify new family members. We described 22 members of the Egh16-like gene family in the Pp MT2006 genome and 18 in the UFV02 and K8108 genomes, highlighting a family expansion. Family members have a small signal peptide, conserved cysteine-rich R/Y/FxC motifs in the C-terminal region, and a virulence-related Egh16-like domain and were able to suppress PTI related responses in Benthamiana. Phylogenetic analysis placed the family members into eight clusters, with members induced during the early stages of rust infection. Members of clusters VI and VII are present in different copy numbers in Pp genomes and suppressed PAMP-related responses.

Engineering a One Health Super Wheat

Wheat is the predominant crop worldwide, contributing approximately 20% of protein and calories to the human diet. However, the yield potential of wheat faces limitations due to pests, diseases, and abiotic stresses. Although conventional breeding has improved desirable traits, the use of modern transgenesis technologies has been limited in wheat in comparison to other crops such as maize and soybean. Recent advances in wheat gene cloning and transformation technology now enable the development of a super wheat consistent with the One Health goals of sustainability, food security, and environmental stewardship. This variety combines traits to enhance pest and disease resistance, elevate grain nutritional value, and improve resilience to climate change. In this review, we explore ways to leverage current technologies to combine and transform useful traits into wheat. We also address the requirements of breeders and legal considerations such as patents and regulatory issues.

Evolutionary and immune-activating character analyses of NLR genes in algae suggest the ancient origin of plant intracellular immune receptors

Nucleotide-binding leucine-rich repeat (NLR) proteins are crucial intracellular immune receptors in plants, responsible for detecting invading pathogens and initiating defense responses. While previous studies on the evolution and function of NLR genes were mainly limited to land plants, the evolutionary trajectory and immune-activating character of NLR genes in algae remain less explored. In this study, genome-wide NLR gene analysis was conducted on 44 chlorophyte species across seven classes and seven charophyte species across five classes. A few but variable number of NLR genes, ranging from one to 20, were identified in five chlorophytes and three charophytes, whereas no NLR gene was identified from the remaining algal genomes. Compared with land plants, algal genomes possess fewer or usually no NLR genes, implying that the expansion of NLR genes in land plants can be attributed to their adaptation to the more complex terrestrial pathogen environments. Through phylogenetic analysis, domain composition analysis, and conserved motifs profiling of the NBS domain, we detected shared and lineage-specific features between NLR genes in algae and land plants, supporting the common origin and continuous evolution of green plant NLR genes. Immune-activation assays revealed that both TNL and RNL proteins from green algae can elicit hypersensitive responses in Nicotiana benthamiana, indicating the molecular basis for immune activation has emerged in the early evolutionary stage of different types of NLR proteins. In summary, the results from this study suggest that NLR proteins may have taken a role as intracellular immune receptors in the common ancestor of green plants.

Changes in planta K nutrient content altered the interaction pattern between Nicotiana benthamiana and Alternaria longipes

Potassium (K) fertilisation has frequently been shown to enhance plant resistance against pathogens, though the mechanisms remain elusive. This study investigates the interaction dynamics between Nicotiana benthamiana and the pathogen Alternaria longipes under different planta K levels. On the host side, adding K activated the expressions of three NLR (nucleotide-binding domain and leucine-rich repeat-containing proteins) resistance genes, including NbRPM1, NbR1B23 and NbNBS12. Silencing these NLRs attenuated resistance in high-K (HK, 40.8 g/kg) plant, whereas their overexpression strengthened resistance in low-K (LK, 23.9 g/kg) plant. Typically, these NLRs mainly strengthened plant resistance via promoting the expression of pathogenesis-related genes (PRs), ROS burst and synthesis of antifungal metabolites in HK plant. On the pathogen side, the expression of effectors HKCSP1, HKCSP2 and LKCSP were shown to be related to planta K content. A. longipes mainly expressed effectors HKCSP1 and HKCSP2 in HK plant to interfere host resistance. HKCSP1 physically interacted with NbRPM1 to promote the degradation of NbRPM1, then attenuated related resistance in HK N. benthamiana. Meanwhile, HKCSP2 directly interacted with NbPR5 to suppress resistance in HK plant. In LK plant, A. longipes mainly deployed LKCSP that interacted with NbR1B23 to interfere reduce resistance in N. benthamiana. Overall, our research insights that both pathogen and host mobilise distinct strategies to outcompete each other during interactions in different K nutrient environments.

High-quality chromosome scale genome assemblies of two important Sorghum inbred lines, Tx2783 and RTx436

Sorghum bicolor (L.) Moench is a significant grass crop globally, known for its genetic diversity. High quality genome sequences are needed to capture the diversity. We constructed high-quality, chromosome-level genome assemblies for two vital sorghum inbred lines, Tx2783 and RTx436. Through advanced single-molecule techniques, long-read sequencing and optical maps, we improved average sequence continuity 19-fold and 11-fold higher compared to existing Btx623 v3.0 reference genome and obtained 19 and 18 scaffolds (N50 of 25.6 and 14.4) for Tx2783 and RTx436, respectively. Our gene annotation efforts resulted in 29 612 protein-coding genes for the Tx2783 genome and 29 265 protein-coding genes for the RTx436 genome. Comparative analyses with 26 plant genomes which included 18 sorghum genomes and 8 outgroup species identified around 31 210 protein-coding gene families, with about 13 956 specific to sorghum. Using representative models from gene trees across the 18 sorghum genomes, a total of 72 579 pan-genes were identified, with 14% core, 60% softcore and 26% shell genes. We identified 99 genes in Tx2783 and 107 genes in RTx436 that showed functional enrichment specifically in binding and metabolic processes, as revealed by the GO enrichment Pearson Chi-Square test. We detected 36 potential large inversions in the comparison between the BTx623 Bionano map and the BTx623 v3.1 reference sequence. Strikingly, these inversions were notably absent when comparing Tx2783 or RTx436 with the BTx623 Bionano map. These inversion were mostly in the pericentromeric region which is known to have low complexity regions and harder to assemble and suggests the presence of potential artifacts in the public BTx623 reference assembly. Furthermore, in comparison to Tx2783, RTx436 exhibited 324 883 additional Single Nucleotide Polymorphisms (SNPs) and 16 506 more Insertions/Deletions (INDELs) when using BTx623 as the reference genome. We also characterized approximately 348 nucleotide-binding leucine-rich repeat (NLR) disease resistance genes in the two genomes. These high-quality genomes serve as valuable resources for discovering agronomic traits and structural variation studies.

A viral effector blocks the turnover of a plant NLR receptor to trigger a robust immune response

Plant intracellular nucleotide-binding and leucine-rich repeat immune receptors (NLRs) play a key role in activating a strong pathogen defense response. Plant NLR proteins are tightly regulated and accumulate at very low levels in the absence of pathogen effectors. However, little is known about how this low level of NLR proteins is able to induce robust immune responses upon recognition of pathogen effectors. Here, we report that, in the absence of effector, the inactive form of the tomato NLR Sw-5b is targeted for ubiquitination by the E3 ligase SBP1. Interaction of SBP1 with Sw-5b via only its N-terminal domain leads to slow turnover. In contrast, in its auto-active state, Sw-5b is rapidly turned over as SBP1 is upregulated and interacts with both its N-terminal and NB-LRR domains. During infection with the tomato spotted wilt virus, the viral effector NSm interacts with Sw-5b and disrupts the interaction of Sw-5b with SBP1, thereby stabilizing the active Sw-5b and allowing it to induce a robust immune response.

Allelic variability in the Rpp1 locus conferring resistance to Asian soybean rust revealed by genome-wide association

Soybean is a crucial crop for the Brazilian economy, but it faces challenges from the biotrophic fungus Phakopsora pachyrhizi, which causes Asian Soybean Rust (ASR). In this study, we aimed to identify SNPs associated with resistance within the Rpp1 locus, which is effective against Brazilian ASR populations. We employed GWAS and re-sequencing analyzes to pinpoint SNP markers capable of differentiating between soybean accessions harboring the Rpp1, Rpp1-b and other alternative alleles in the Rpp1 locus and from susceptible soybean cultivars. Seven SNP markers were found to be associated with ASR resistance through GWAS, with three of them defining haplotypes that efficiently distinguished the accessions based on their ASR resistance and source of the Rpp gene. These haplotypes were subsequently validated using a bi-parental population and a diverse set of Rpp sources, demonstrating that the GWAS markers co-segregate with ASR resistance. We then examined the presence of these haplotypes in a diverse set of soybean genomes worldwide, finding a few new potential sources of Rpp1/Rpp1-b. Further genomic sequence analysis revealed nucleotide differences within the genes present in the Rpp1 locus, including the ULP1-NBS-LRR genes, which are potential R gene candidates. These results provide valuable insights into ASR resistance in soybean, thus helping the development of resistant soybean varieties through genetic breeding programs.

Plant pangenomes for crop improvement, biodiversity and evolution

Plant genome sequences catalogue genes and the genetic elements that regulate their expression. Such inventories further research aims as diverse as mapping the molecular basis of trait diversity in domesticated plants or inquiries into the origin of evolutionary innovations in flowering plants millions of years ago. The transformative technological progress of DNA sequencing in the past two decades has enabled researchers to sequence ever more genomes with greater ease. Pangenomes - complete sequences of multiple individuals of a species or higher taxonomic unit - have now entered the geneticists' toolkit. The genomes of crop plants and their wild relatives are being studied with translational applications in breeding in mind. But pangenomes are applicable also in ecological and evolutionary studies, as they help classify and monitor biodiversity across the tree of life, deepen our understanding of how plant species diverged and show how plants adapt to changing environments or new selection pressures exerted by human beings.

Engineering disease-resistant plants with alternative translation efficiency by switching uORF types through CRISPR

Engineering disease-resistant plants can be a powerful solution to the issue of food security. However, it requires addressing two fundamental questions: what genes to express and how to control their expressions. To find a solution, we screen CRISPR-edited upstream open reading frame (uORF) variants in rice, aiming to optimize translational control of disease-related genes. By switching uORF types of the 5'-leader from Arabidopsis TBF1, we modulate the ribosome accessibility to the downstream firefly luciferase. We assume that by switching uORF types using CRISPR, we could generate uORF variants with alternative translation efficiency (CRISPR-aTrE-uORF). These variants, capable of boosting translation for resistance-associated genes and dampening it for susceptible ones, can help pinpoint previously unidentified genes with optimal expression levels. To test the assumption, we screened edited uORF variants and found that enhanced translational suppression of the plastic glutamine synthetase 2 can provide broad-spectrum disease resistance in rice with minimal fitness costs. This strategy, which involves modifying uORFs from none to some, or from some to none or different ones, demonstrates how translational agriculture can speed up the development of disease-resistant crops. This is vital for tackling the food security challenges we face due to growing populations and changing climates.

Designer TALEs enable discovery of cell death-inducer genes

Transcription activator-like effectors (TALEs) in plant-pathogenic Xanthomonas bacteria activate expression of plant genes and support infection or cause a resistance response. PthA4AT is a TALE with a particularly short DNA-binding domain harboring only 7.5 repeats which triggers cell death in Nicotiana benthamiana; however, the genetic basis for this remains unknown. To identify possible target genes of PthA4AT that mediate cell death in N. benthamiana, we exploited the modularity of TALEs to stepwise enhance their specificity and reduce potential target sites. Substitutions of individual repeats suggested that PthA4AT-dependent cell death is sequence specific. Stepwise addition of repeats to the C-terminal or N-terminal end of the repeat region narrowed the sequence requirements in promoters of target genes. Transcriptome profiling and in silico target prediction allowed the isolation of two cell death inducer genes, which encode a patatin-like protein and a bifunctional monodehydroascorbate reductase/carbonic anhydrase protein. These two proteins are not linked to known TALE-dependent resistance genes. Our results show that the aberrant expression of different endogenous plant genes can cause a cell death reaction, which supports the hypothesis that TALE-dependent executor resistance genes can originate from various plant processes. Our strategy further demonstrates the use of TALEs to scan genomes for genes triggering cell death and other relevant phenotypes.

Transcriptome analysis of resistant and susceptible Medicago truncatula genotypes in response to spring black stem and leaf spot disease

Ascochyta blights cause yield losses in all major legume crops. Spring black stem (SBS) and leaf spot disease is a major foliar disease of Medicago truncatula and Medicago sativa (alfalfa) caused by the necrotrophic fungus Ascochyta medicaginicola. This present study sought to identify candidate genes for SBS disease resistance for future functional validation. We employed RNA-seq to profile the transcriptomes of a resistant (HM078) and susceptible (A17) genotype of M. truncatula at 24, 48, and 72 h post inoculation. Preliminary microscopic examination showed reduced pathogen growth on the resistant genotype. In total, 192 and 2,908 differentially expressed genes (DEGs) were observed in the resistant and susceptible genotype, respectively. Functional enrichment analysis revealed the susceptible genotype engaged in processes in the cell periphery and plasma membrane, as well as flavonoid biosynthesis whereas the resistant genotype utilized calcium ion binding, cell wall modifications, and external encapsulating structures. Candidate genes for disease resistance were selected based on the following criteria; among the top ten upregulated or downregulated genes in the resistant genotype, upregulated over time in the resistant genotype, hormone pathway genes, plant disease resistance genes, receptor-like kinases, contrasting expression profiles in QTL for disease resistance, and upregulated genes in enriched pathways. Overall, 22 candidate genes for SBS disease resistance were identified with support from the literature. These genes will be sources for future targeted mutagenesis and candidate gene validation potentially helping to improve disease resistance to this devastating foliar pathogen.