Nucleotide-binding Site Leucine-rich Repeat Research Articles

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 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.

Transcriptomic and Metabolomic Analyses of the Piz-t-Mediated Resistance in Rice against Magnaporthe oryzae.

Magnaporthe oryzae causes devastating rice blast disease, significantly impacting rice production in many countries. Among the many known resistance (R) genes, Piz-t confers broad-spectrum resistance to M. oryzae isolates and encodes a nucleotide-binding site leucine-rich repeat receptor (NLR). Although Piz-t-interacting proteins and those in the signal transduction pathway have been identified over the last decade, the Piz-t-mediated resistance has not been fully understood at the transcriptomic and metabolomic levels. In this study, we performed transcriptomic and metabolomic analyses in the Piz-t plants after inoculation with M. oryzae. The transcriptomic analysis identified a total of 15,571 differentially expressed genes (DEGs) from infected Piz-t and wild-type plants, with 2791 being Piz-t-specific. K-means clustering, GO term analysis, and KEGG enrichment pathway analyses of the total DEGs identified five groups of DEGs with distinct gene expression patterns at different time points post inoculation. GO term analysis of the 2791 Piz-t-specific DEGs revealed that pathways related to DNA organization, gene expression regulation, and cell division were highly enriched in the group, especially at early infection stages. The gene expression patterns in the transcriptomic datasets were well correlated with the metabolomic profiling. Broad-spectrum "pathway-level" metabolomic analyses indicated that terpenoid, phenylpropanoid, flavonoid, fatty acid, amino acid, glycolysis/TCA, and phenylalanine pathways were altered in the Piz-t plants after M. oryzae infection. This study offers new insights into the molecular dynamics of transcripts and metabolites in R-gene-mediated resistance against M. oryzae and provides candidates for enhancing rice blast resistance through the engineering of metabolic pathways.

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.

A Review on Genetic Mechanisms of Plant-pathogen Resistance in Crop Breeding

Plant-pathogen resistance is a critical component of sustainable agriculture, essential for protecting crops from devastating diseases and ensuring global food security. This review explores the genetic mechanisms underlying plant-pathogen resistance, focusing on advances in breeding strategies and genetic engineering. Resistance (R) genes, the cornerstone of plant immunity, are categorized by their structural features, including nucleotide-binding site-leucine-rich repeat (NBS-LRR) domains, and function through pathways such as Effector-Triggered Immunity (ETI). The salicylic acid (SA) pathway, crucial for Systemic Acquired Resistance (SAR), and the jasmonic acid (JA) and ethylene (ET) pathways, which drive Induced Systemic Resistance (ISR), are pivotal in orchestrating plant defense responses. Emerging molecular tools like CRISPR-Cas9 enable precise gene editing to enhance R gene function and target susceptibility (S) genes, offering novel pathways to engineer durable resistance. Transgenic approaches, including the introduction of novel R genes and the expression of antimicrobial proteins, have expanded the genetic toolkit for combating pathogens. RNA interference (RNAi) technology further allows for the silencing of critical pathogen genes, adding a layer of defense. Traditional breeding methods, such as hybridization and backcrossing, remain integral, particularly when combined with Marker-Assisted Selection (MAS) and Genomic Selection (GS). MAS facilitates the efficient incorporation of resistance traits using molecular markers, while GS leverages genome-wide data to predict resistance, significantly enhancing breeding efficiency. Challenges such as the rapid evolution of pathogens, resistance breakdown, and climate change-induced shifts in disease dynamics pose significant threats. These challenges necessitate an integrated approach, combining genetic and genomic tools with sustainable disease management practices, such as the use of beneficial microorganisms, precision agriculture, and diversified cropping systems. Future research must focus on understanding the molecular basis of resistance durability, improving predictive models for resistance traits, and developing climate-resilient crop varieties. This integrated strategy is crucial for mitigating disease impact, enhancing crop resilience, and ensuring sustainable agricultural productivity in the face of environmental and biological challenges.

Identification of RppSLN from an Elite Landrace: A Major Locus Conferring Resistance to Southern Corn Rust in Maize (Zea mays L.).

Southern corn rust (SCR) is one of the most destructive foliar diseases in maize (Zea mays L.), resulting in significant yield losses. Therefore, the continuous identification of disease-resistant germplasm and the deployment of resistant hybrids is essential for durably controlling SCR. The objective of this research was to identify and characterize resistance loci against SCR in maize to expand disease management strategies. Here, we identified a maize landrace with high resistance to SCR 'Silunuo' (SLN) approaching complete immunity. We backcrossed it with a susceptible inbred line, N531, to generate a stable SCR-resistant introgression line N531_R. By crossing it with F35 (a susceptible inbred line), we created a large F2 segregating population and mapped a major SCR-resistant locus on chromosome 10, known as RppSLN. Based on the genome assembly and annotation, we found that RppSLN harbors two NBS-LRR (nucleotide binding site-leucine-rich repeat) genes, namely Zmays10G000430 and Zmays10G000440. These NBS-LRR genes were significantly induced during artificial inoculation with Puccinia polysora, suggesting that they might be candidate genes collectively contributing to the resistance level at this locus. In conclusion, this study identified a major SCR resistance locus directly isolated from a landrace, providing valuable support and information for expanding new disease-resistant germplasms and promoting the utilization of landraces.

Parental assigned chromosomes for cultivated cacao provides insights into genetic architecture underlying resistance to vascular streak dieback.

Diseases of Theobroma cacao L. (Malvaceae) disrupt cocoa bean supply and economically impact growers. Vascular streak dieback (VSD), caused by Ceratobasidium theobromae, is a new encounter disease of cacao currently contained to southeast Asia and Melanesia. Resistance to VSD has been tested with large progeny trials in Sulawesi, Indonesia, and in Papua New Guinea with the identification of informative quantitative trait loci (QTLs). Using a VSD susceptible progeny tree (clone 26), derived from a resistant and susceptible parental cross, we assembled the genome to chromosome-level and discriminated alleles inherited from either resistant or susceptible parents. The parentally phased genomes were annotated for all predicted genes and then specifically for resistance genes of the nucleotide-binding site leucine-rich repeat class (NLR). On investigation, we determined the presence of NLR clusters and other potential disease response gene candidates in proximity to informative QTLs. We identified structural variants within NLRs inherited from parentals. We present the first diploid, fully scaffolded, and parentally phased genome resource for T. cacao L. and provide insights into the genetics underlying resistance and susceptibility to VSD.

Functional genomic regions associated with blast disease resistance in rice predicted syntenic orthologs and potential resistance gene candidates from diverse cereal genomes

Blast disease is a major production constraint in cereal crops worldwide. Genome regions associated with blast resistance in rice were used in homology-based prediction of resistance gene orthologs across cereals. Seventy-four Resistance Gene Analogs (RGAs) that were collocated with rice QTLs (Quantitative Trait Loci) associated with blast resistance, predicted 89 orthologs from cereals,including 61 from finger millet. The RGA orthologs found hits in cereal transcriptomes derived from blast-infected tissues. Over 92% of the putative RGAs encoded NBS-LRR (Nucleotide Binding Site -Leucine Rich Repeat) proteins. Despite conserved primary protein structures, NBS-LRRs were variable in the encoding genes. Primers designed on conserved NBS-LRRs motifs amplified multiple fragments in PCR indicating the presence of highly similar paralogs in genomes. Rice chromosomes 1, 2, 4, 6, and 11 dock clusters of RGAs and syntenic clusters of orthologous RGAs were predicted from other cereal genomes identifying genome hotspots for resistance gene cassettes. RGAs in such cassettes were tightly linked with 50 %–90 % within-cluster similarity. Local finger millet germplasm identified multi-modes of resistance, and lack of correlation between the resistance traits points to independent expression of resistance mechanisms and associated genes in different tissues and development stages. The significant diversity, genomic abundance, and potential functional redundancy complicate use of RGAs for resistance breeding in given host genetic backgrounds, pathogen pools and agro-climates; therefore, robust technology pipelines that enable system-level analysis of expression and effectiveness can increase the practical use of RGAs.

Linkage Mapping and Genome-Wide Association Study Identified Two Peanut Late Leaf Spot Resistance Loci, PLLSR-1 and PLLSR-2, Using Nested Association Mapping.

Identification of candidate genes and molecular markers for late leaf spot (LLS) disease resistance in peanut (Arachis hypogaea) has been a focus of molecular breeding for the U.S. industry-funded peanut genome project. Efforts have been hindered by limited mapping resolution due to low levels of genetic recombination and marker density available in traditional biparental mapping populations. To address this, a multi-parental nested association mapping population has been genotyped with the peanut 58K single-nucleotide polymorphism (SNP) array and phenotyped for LLS severity in the field for 3 years. Joint linkage-based quantitative trait locus (QTL) mapping identified nine QTLs for LLS resistance with significant phenotypic variance explained up to 47.7%. A genome-wide association study identified 13 SNPs consistently associated with LLS resistance. Two genomic regions harboring the consistent QTLs and SNPs were identified from 1,336 to 1,520 kb (184 kb) on chromosome B02 and from 1,026.9 to 1,793.2 kb (767 kb) on chromosome B03, designated as peanut LLS resistance loci, PLLSR-1 and PLLSR-2, respectively. PLLSR-1 contains 10 nucleotide-binding site leucine-rich repeat disease resistance genes. A nucleotide-binding site leucine-rich repeat disease resistance gene, Arahy.VKVT6A, was also identified on homoeologous chromosome A02. PLLSR-2 contains five significant SNPs associated with five different genes encoding callose synthase, pollen defective in guidance protein, pentatricopeptide repeat, acyl-activating enzyme, and C2 GRAM domains-containing protein. This study highlights the power of multi-parent populations such as nested association mapping for genetic mapping and marker-trait association studies in peanuts. Validation of these two LLS resistance loci will be needed for marker-assisted breeding.

Genome and transcriptome exploration reveals receptor-like kinases as potential resistance gene analogs against bacterial blight in pomegranate.

Pomegranate (Punica granatum L.) is a tropical fruit crop of pharma-nutritional importance. However, it faces farming challenges due to pests and diseases, particularly bacterial blight and wilt. Developing resistant cultivars is crucial for sustainable pomegranate cultivation, and understanding resistance's genetic basis is essential. We used an extensive resistance gene analogues (RGA) prediction tool to identify 958 RGAs, classified into Nucleotide Binding Site-leucine-rich repeat (NBS-LRR) proteins, receptor-like kinases (RLKs), receptor-like proteins (RLPs), Transmembrane coiled-coil (TM-CC), and nine non-canonical RGAs. RGAs were distributed across all eight chromosomes, with chromosome 02 containing the most RGAs (161), and chromosome 08 having the highest density (4.42 RGA/Mb). NBS-LRR genes were predominantly present on chromosomes 08 and 02, whereas RLKs and RLPs were primarily located on chromosomes 04 and 07. Gene ontology analysis revealed that 475 RGAs were associated with defence against various biotic stresses. Using RNAseq, we identified 120 differentially expressed RGAs, with RLKs (74) being prominent among the differentially expressed genes. The discovery of these RGAs is a significant step towards breeding pomegranates for pest and disease resistance. The differentially expressed RLKs hold promise for developing resistant cultivars against bacterial blight, thereby contributing to the sustainability of pomegranate cultivation.

Genome-Wide Identification of Nucleotide-Binding Site–Leucine-Rich Repeat Gene Family in Cymbidium ensifolium and Expression Profiles in Response to Fusarium Wilt Infection

Genome-Wide Identification of Nucleotide-Binding Site–Leucine-Rich Repeat Gene Family in Cymbidium ensifolium and Expression Profiles in Response to Fusarium Wilt Infection

Cytological and molecular characterization of wheat lines carrying leaf rust and stem rust resistance genes Lr24 and Sr24

Previous studies showed that Australian wheat cultivars Janz and Sunco carry leaf rust and stem rust resistance genes Lr24 and Sr24 derived from Thinopyrum ponticum chromosome arm 3AgL. However, the size of the alien segments carrying Lr24 and Sr24 in the lines were not determined. In this study, we used non-denaturing fluorescence in situ hybridization (ND-FISH), genomic in situ hybridization (GISH), and PCR-based landmark unique gene (PLUG) markers to visualize the alien segments in Janz and Sunco, and further compared them with the segments in US cultivars Agent and Amigo. The fraction length (FL) of the alien translocation in Agent was 0.70–1.00, whereas those in Janz, Sunco, and Amigo were smaller, at FL 0.85–1.00. It was deduced that the alien gene RAg encoding for red grain color and rust resistance genes Lr24 and Sr24 on chromosome arm 3AgL were in bins of FL 0.70–0.85 and 0.85–1.00, respectively. We retrieved and extracted nucleotide-binding site-leucine-rich repeat (NBS-LRR) receptor genes corresponding to the region of Lr24 and Sr24 on chromosomes 3E, and 3J, 3Js and 3St from the reference genome sequences of Th. elongatum and Th. intermedium, respectively. A set of molecular markers developed for Lr24 and Sr24 from those extracted NBS-LRR genes will provide valuable information for fine mapping and cloning of these genes.

GWAS analysis reveals the genetic basis of blast resistance associated with heading date in rice.

Rice blast is a destructive fungal disease affecting rice plants at various growth stages, significantly threatening global yield stability. Development of resistant rice cultivars stands as a practical means of disease control. Generally, association mapping with a diversity panel powerfully identifies new alleles controlling trait of interest. On the other hand, utilization of a breeding panel has its advantage that can be directly applied in a breeding program. In this study, we conducted a genome-wide association study (GWAS) for blast resistance using 296 commercial rice cultivars with low population structure but large phenotypic diversity. We attempt to answer the genetic basis behind rice blast resistance among early maturing cultivars by subdividing the population based on its Heading date 1 (Hd1) functionality. Subpopulation-specific GWAS using the mixed linear model (MLM) based on blast nursery screening conducted in three years revealed a total of 26 significant signals, including three nucleotide-binding site leucine-rich repeat (NBS-LRR) genes (Os06g0286500, Os06g0286700, and Os06g0287500) located at Piz locus on chromosome 6, and one at the Pi-ta locus (Os12g0281300) on chromosome 12. Haplotype analysis revealed blast resistance associated with Piz locus was exclusively specific to Type 14 hd1 among japonica rice. Our findings provide valuable insights for breeding blast resistant rice and highlight the applicability of our elite cultivar panel to detect superior alleles associated with important agronomic traits.

Insights into the genetic architecture of Phytophthora capsici root rot resistance in chile pepper (Capsicum spp.) from multi-locus genome-wide association study

BackgroundPhytophthora root rot, a major constraint in chile pepper production worldwide, is caused by the soil-borne oomycete, Phytophthora capsici. This study aimed to detect significant regions in the Capsicum genome linked to Phytophthora root rot resistance using a panel consisting of 157 Capsicum spp. genotypes. Multi-locus genome wide association study (GWAS) was conducted using single nucleotide polymorphism (SNP) markers derived from genotyping-by-sequencing (GBS). Individual plants were separately inoculated with P. capsici isolates, ‘PWB-185’, ‘PWB-186’, and ‘6347’, at the 4–8 leaf stage and were scored for disease symptoms up to 14-days post-inoculation. Disease scores were used to calculate disease parameters including disease severity index percentage, percent of resistant plants, area under disease progress curve, and estimated marginal means for each genotype.ResultsMost of the genotypes displayed root rot symptoms, whereas five accessions were completely resistant to all the isolates and displayed no symptoms of infection. A total of 55,117 SNP markers derived from GBS were used to perform multi-locus GWAS which identified 330 significant SNP markers associated with disease resistance. Of these, 56 SNP markers distributed across all the 12 chromosomes were common across the isolates, indicating association with more durable resistance. Candidate genes including nucleotide-binding site leucine-rich repeat (NBS-LRR), systemic acquired resistance (SAR8.2), and receptor-like kinase (RLKs), were identified within 0.5 Mb of the associated markers.ConclusionsResults will be used to improve resistance to Phytophthora root rot in chile pepper by the development of Kompetitive allele-specific markers (KASP®) for marker validation, genomewide selection, and marker-assisted breeding.

Genome-wide characterization of the NBLRR gene family provides evolutionary and functional insights into blast resistance in pearl millet (Cenchrusamericanus (L.) Morrone).

The investigation is the first report on genome-wide identification and characterization of NBLRR genes in pearl millet. We have shown the role of gene loss and purifying selection in the divergence of NBLRRs in Poaceae lineage and candidate CaNBLRR genes for resistance to Magnaporthe grisea infection. Plants have evolved multiple integral mechanisms to counteract the pathogens' infection, among which plant immunity through NBLRR (nucleotide-binding site, leucine-rich repeat) genes is at the forefront. The genome-wide mining in pearl millet (Cenchrus americanus (L.) Morrone) revealed 146 CaNBLRRs. The variation in the branch length of NBLRRs showed the dynamic nature of NBLRRs in response to evolving pathogen races. The orthology of NBLRRs showed a predominance of many-to-one orthologs, indicating the divergence of NBLRRs in the pearl millet lineage mainly through gene loss events followed by gene gain through single-copy duplications. Further, the purifying selection (Ka/Ks < 1) shaped the expansion of NBLRRs within the lineage of pear millet and other members of Poaceae. Presence of cis-acting elements, viz. TCA element, G-box, MYB, SARE, ABRE and conserved motifs annotated with P-loop, kinase 2, RNBS-A, RNBS-D, GLPL, MHD, Rx-CC and LRR suggests their putative role in disease resistance and stress regulation. The qRT-PCR analysis in pearl millet lines showing contrasting responses to Magnaporthe grisea infection identified CaNBLRR20, CaNBLRR33, CaNBLRR46 CaNBLRR51, CaNBLRR78 and CaNBLRR146 as putative candidates. Molecular docking showed the involvement of three and two amino acid residues of LRR domains forming hydrogen bonds (histidine, arginine and threonine) and salt bridges (arginine and lysine) with effectors. Whereas 14 and 20 amino acid residues of CaNBLRR78 and CaNBLRR20 showed hydrophobic interactions with 11 and 9 amino acid residues of effectors, Mg.00g064570.m01 and Mg.00g006570.m01, respectively. The present investigation gives a comprehensive overview of CaNBLRRs and paves the foundation for their utility in pearl millet resistance breeding through understanding of host-pathogen interactions.

The Soybean Rpp3 Gene Encodes a TIR-NBS-LRR Protein that Confers Resistance to Phakopsora pachyrhizi.

Soybean rust is an economically significant disease caused by the fungus Phakopsora pachyrhizi that negatively impacts soybean (Glycine max [L.] Merr.) production throughout the world. Susceptible plants infected by P. pachyrhizi develop tan-colored lesions on the leaf surface that give rise to funnel-shaped uredinia as the disease progresses. While most soybean germplasm is susceptible, seven genetic loci (Rpp1 to Rpp7) that provide race-specific resistance to P. pachyrhizi (Rpp) have been identified. Rpp3 was first discovered and characterized in the soybean accession PI 462312 (Ankur), and it was also determined to be one of two Rpp genes present in PI 506764 (Hyuuga). Genetic crosses with PI 506764 were later used to fine-map the Rpp3 locus to a 371-kb region on chromosome 6. The corresponding region in the susceptible Williams 82 (Wm82) reference genome contains several homologous nucleotide binding site-leucine rich repeat (NBS-LRR) genes. To identify Rpp3, we designed oligonucleotide primers to amplify Rpp3 candidate (Rpp3C) NBS-LRR genes at this locus from PI 462312, PI 506764, and Wm82 using polymerase chain reaction (PCR). Five Rpp3C genes were identified in both Rpp3-resistant soybean lines, and co-silencing these genes compromised resistance to P. pachyrhizi. Gene expression analysis and sequence comparisons of the Rpp3C genes in PI 462312 and PI 506764 suggest that a single candidate gene, Rpp3C3, is responsible for Rpp3-mediated resistance. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 "No Rights Reserved" license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024.

Development of NBS-LRR gene-specific microsatellite markers for passion fruit Passiflora edulis Sims

The chromosome-level genome assembly of passion fruit (Passiflora edulis Sims) has facilitated computational analyses in developing novel informative SSR markers for genetics and breeding research. In this study, in-silico analysis was conducted to discover potential microsatellite loci and to design specific primers from the sequences of the characterised nucleotide-binding site - leucine-rich repeats (NBS-LRR) gene family of passion fruit, and a genotyping experiment was performed to validate the novel simple sequence repeat (SSR) markers.In total, 497 microsatellite loci were detected from 161 passion fruit NBS-LRR genes, of which 383 loci were qualified for primer generation. Forty-six SSR markers were selected for polymorphism verification, targeting 35 NBS-LRR genes that showed potential gene expression in response to biotic and abiotic stresses. From that, 25 SSR markers showed consistent polymorphic alleles among different passion fruit genotypes via PCR-PAGE analysis. These novel NBS-LRR-specific SSR markers might provide valuable tools for fortifying research on germplasm evaluation, genetic mapping, and molecular breeding for disease-resistant passion fruit varieties.

Genome-Wide Association Study Reveals Polygenic Architecture for Limber Pine Quantitative Disease Resistance to White Pine Blister Rust.

Development of durable resistance effective against a broad range of pathotypes is crucial for restoration of pathogen-damaged ecosystems. This study dissected the complex genetic architecture for limber pine quantitative disease resistance (QDR) to Cronartium ribicola using a genome-wide association study. Eighteen-month-old seedlings were inoculated for resistance screening under controlled conditions. Disease development was quantitatively assessed for QDR-related traits over 4 years postinoculation. To reveal the genomic architecture contributing to QDR-related traits, a set of genes related to disease resistance with genome-wide distribution was selected for targeted sequencing for genotyping of single-nucleotide polymorphisms (SNPs). The genome-wide association study revealed a set of SNPs significantly associated with quantitative traits for limber pine QDR to white pine blister rust, including number of needle spots and stem cankers, as well as survival 4 years postinoculation. The peaks of marker-trait associations displayed a polygenic pattern, with genomic regions as potential resistant quantitative trait loci, distributed over 10 of the 12 linkage groups (LGs) of Pinus. None of them was linked to the Cr4-controlled major gene resistance previously mapped on LG08. Both normal canker and bole infection were mapped on LG05, and the associated SNPs explained their phenotypic variance up to 52%, tagging a major resistant quantitative trait locus. Candidate genes containing phenotypically associated SNPs encoded putative nucleotide-binding site leucine-rich repeat proteins, leucine-rich repeat-receptor-like kinase, cytochrome P450 superfamily protein, heat shock cognate protein 70, glutamate receptor, RNA-binding family protein, and unknown protein. The confirmation of resistant quantitative trait loci broadens the genetic pool of limber pine resistance germplasm for resistance breeding.

Genome-wide identification and characterization of NBLRR genes in finger millet (Eleusine coracana L.) and their expression in response to Magnaporthe grisea infection

BackgroundThe nucleotide binding site leucine rich repeat (NBLRR) genes significantly regulate defences against phytopathogens in plants. The genome-wide identification and analysis of NBLRR genes have been performed in several species. However, the detailed evolution, structure, expression of NBLRRs and functional response to Magnaporthe grisea are unknown in finger millet (Eleusine coracana (L.) Gaertn.).ResultsThe genome-wide scanning of the finger millet genome resulted in 116 NBLRR (EcNBLRRs1-116) encompassing 64 CC-NB-LRR, 47 NB-LRR and 5 CCR-NB-LRR types. The evolutionary studies among the NBLRRs of five Gramineae species, viz., purple false brome (Brachypodium distachyon (L.) P.Beauv.), finger millet (E. coracana), rice (Oryza sativa L.), sorghum (Sorghum bicolor L. (Moench)) and foxtail millet (Setaria italica (L.) P.Beauv.) showed the evolution of NBLRRs in the ancestral lineage of the target species and subsequent divergence through gene-loss events. The purifying selection (Ka/Ks < 1) shaped the expansions of NBLRRs paralogs in finger millet and orthologs among the target Gramineae species. The promoter sequence analysis showed various stress- and phytohormone-responsive cis-acting elements besides growth and development, indicating their potential role in disease defence and regulatory mechanisms. The expression analysis of 22 EcNBLRRs in the genotypes showing contrasting responses to Magnaporthe grisea infection revealed four and five EcNBLRRs in early and late infection stages, respectively. The six of these nine candidate EcNBLRRs proteins, viz., EcNBLRR21, EcNBLRR26, EcNBLRR30, EcNBLRR45, EcNBLRR55 and EcNBLRR76 showed CC, NB and LRR domains, whereas the EcNBLRR23, EcNBLRR32 and EcNBLRR83 showed NB and LRR somains.ConclusionThe identification and expression analysis of EcNBLRRs showed the role of EcNBLRR genes in assigning blast resistance in finger millet. These results pave the foundation for in-depth and targeted functional analysis of EcNBLRRs through genome editing and transgenic approaches.

Uncovering the transcriptional responses of tobacco (Nicotiana tabacum L.) roots to Ralstonia solanacearum infection: a comparative study of resistant and susceptible cultivars

BackgroundTobacco bacterial wilt (TBW) caused by Ralstonia solanacearum is the most serious soil-borne disease of tobacco that significantly reduces crop yield. However, the limited availability of resistance in tobacco hinders breeding efforts for this disease.ResultsIn this study, we conducted hydroponic experiments for the root expression profiles of D101 (resistant) and Honghuadajinyuan (susceptible) cultivars in response to BW infection at 0 h, 6 h, 1 d, 3 d, and 7d to explore the defense mechanisms of BW resistance in tobacco. As a result, 20,711 and 16,663 (total: 23,568) differentially expressed genes (DEGs) were identified in the resistant and susceptible cultivars, respectively. In brief, at 6 h, 1 d, 3 d, and 7 d, the resistant cultivar showed upregulation of 1553, 1124, 2583, and 7512 genes, while the susceptible cultivar showed downregulation of 1213, 1295, 813, and 7735 genes. Similarly, across these time points, the resistant cultivar had downregulation of 1034, 749, 1686, and 11,086 genes, whereas the susceptible cultivar had upregulation of 1953, 1790, 2334, and 6380 genes. The resistant cultivar had more up-regulated genes at 3 d and 7 d than the susceptible cultivar, indicating that the resistant cultivar has a more robust defense response against the pathogen. The GO and KEGG enrichment analysis showed that these genes are involved in responses to oxidative stress, plant–pathogen interactions, cell walls, glutathione and phenylalanine metabolism, and plant hormone signal transduction. Among the DEGs, 239 potential candidate genes were detected, including 49 phenylpropane/flavonoids pathway-associated, 45 glutathione metabolic pathway-associated, 47 WRKY, 48 ERFs, eight ARFs, 26 pathogenesis-related genes (PRs), and 14 short-chain dehydrogenase/reductase genes. In addition, two highly expressed novel genes (MSTRG.61386-R1B-17 and MSTRG.61568) encoding nucleotide-binding site leucine-rich repeat (NBS-LRR) proteins were identified in both cultivars at 7 d.ConclusionsThis study revealed significant enrichment of DEGs in GO and KEGG terms linked to glutathione, flavonoids, and phenylpropane pathways, indicating the potential role of glutathione and flavonoids in early BW resistance in tobacco roots. These findings offer fundamental insight for further exploration of the genetic architecture and molecular mechanisms of BW resistance in tobacco and solanaceous plants at the molecular level.