RESUMO
Powdery mildew, a potentially severe crop disease, can be controlled by mlo mutations, which suppress fungal proliferation but typically also reduce yield. Li et al. (2022) demonstrate that productivity can be restored by overexpressing a host sugar transporter, thus offering a new option for economically and environmentally benign disease control.
Assuntos
Ascomicetos , Doenças das Plantas , Ascomicetos/genética , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Proteínas de Plantas/genéticaRESUMO
Induced mutations have been used to generate novel variation for breeding purposes since the early 1900s. However, the combination of this old technology with the new capabilities of high-throughput sequencing has resulted in powerful reverse genetic approaches in polyploid crops. Sequencing genomes or exomes of large mutant populations can generate extensive databases of mutations for most genes. These mutant collections, together with genome editing, are being used in polyploid species to combine mutations in all copies of a gene (homoeologs), and to expose phenotypic variation that was previously hidden by functional redundancy among homoeologs. This redundancy is more extensive in recently formed polyploids such as wheat, which can now benefit from the deployment of useful recessive mutations previously identified in its diploid relatives. Sequenced mutant populations and genome editing have changed the paradigm of what is possible in functional genetic analysis of wheat.
Assuntos
Edição de Genes/métodos , Variação Genética , Genoma de Planta , Sequenciamento de Nucleotídeos em Larga Escala , Mutagênese , Triticum/genética , Sequência de Bases , Mutação , Melhoramento Vegetal/métodos , Poliploidia , Genética ReversaRESUMO
Aegilops is a close relative of wheat (Triticum spp.), and Aegilops species in the section Sitopsis represent a rich reservoir of genetic diversity for the improvement of wheat. To understand their diversity and advance their utilization, we produced whole-genome assemblies of Aegilops longissima and Aegilops speltoides. Whole-genome comparative analysis, along with the recently sequenced Aegilops sharonensis genome, showed that the Ae. longissima and Ae. sharonensis genomes are highly similar and are most closely related to the wheat D subgenome. By contrast, the Ae. speltoides genome is more closely related to the B subgenome. Haplotype block analysis supported the idea that Ae. speltoides genome is closest to the wheat B subgenome, and highlighted variable and similar genomic regions between the three Aegilops species and wheat. Genome-wide analysis of nucleotide-binding leucine-rich repeat (NLR) genes revealed species-specific and lineage-specific NLR genes and variants, demonstrating the potential of Aegilops genomes for wheat improvement.
Assuntos
Aegilops , Aegilops/genética , Genoma de Planta/genética , Filogenia , Poaceae/genética , Triticum/genéticaRESUMO
Staying ahead of the arms race against rust and mildew diseases in cereal crops is essential to maintain and preserve food security. The methodological challenges associated with conventional resistance breeding are major bottlenecks for deploying resistance (R) genes in high-yielding crop varieties. Advancements in our knowledge of plant genomes, structural mechanisms, innovations in bioinformatics, and improved plant transformation techniques have alleviated this bottleneck by permitting rapid gene isolation, functional studies, directed engineering of synthetic resistance and precise genome manipulation in elite crop cultivars. Most cloned cereal R genes encode canonical immune receptors which, on their own, are prone to being overcome through selection for resistance-evading pathogenic strains. However, the increasingly large repertoire of cloned R genes permits multi-gene stacking that, in principle, should provide longer-lasting resistance. This review discusses how these genomics-enabled developments are leading to new breeding and biotechnological opportunities to achieve durable rust and powdery mildew control in cereals.
Assuntos
Basidiomycota , Hordeum , Grão Comestível/genética , Triticum/genética , Resistência à Doença/genética , Melhoramento Vegetal , Doenças das Plantas/genética , Doenças das Plantas/prevenção & controleRESUMO
Aegilops tauschii is the diploid progenitor of the wheat D subgenome and a valuable resource for wheat breeding, yet, genetic analysis of resistance against Fusarium head blight (FHB) and the major Fusarium mycotoxin deoxynivalenol (DON) is lacking. We treated a panel of 147 Ae. tauschii accessions with either Fusarium graminearum spores or DON solution and recorded the associated disease spread or toxin-induced bleaching. A k-mer-based association mapping pipeline dissected the genetic basis of resistance and identified candidate genes. After DON infiltration nine accessions revealed severe bleaching symptoms concomitant with lower conversion rates of DON into the non-toxic DON-3-O-glucoside. We identified the gene AET5Gv20385300 on chromosome 5D encoding a uridine diphosphate (UDP)-glucosyltransferase (UGT) as the causal variant and the mutant allele resulting in a truncated protein was only found in the nine susceptible accessions. This UGT is also polymorphic in hexaploid wheat and when expressed in Saccharomyces cerevisiae only the full-length gene conferred resistance against DON. Analysing the D subgenome helped to elucidate the genetic control of FHB resistance and identified a UGT involved in DON detoxification in Ae. tauschii and hexaploid wheat. This resistance mechanism is highly conserved since the UGT is orthologous to the barley UGT HvUGT13248 indicating descent from a common ancestor of wheat and barley.
Assuntos
Aegilops , Fusarium , Triticum/genética , Triticum/metabolismo , Glucosiltransferases/genética , Difosfato de Uridina , Melhoramento Vegetal , Doenças das Plantas/genética , Resistência à Doença/genéticaRESUMO
Crop production needs to increase to secure future food supplies, while reducing its impact on ecosystems. Detailed characterization of plant genomes and genetic diversity is crucial for meeting these challenges. Advances in genome sequencing and assembly are being used to access the large and complex genomes of crops and their wild relatives. These have helped to identify a wide spectrum of genetic variation and permitted the association of genetic diversity with diverse agronomic phenotypes. In combination with improved and automated phenotyping assays and functional genomic studies, genomics is providing new foundations for crop-breeding systems.
Assuntos
Produção Agrícola/métodos , Produtos Agrícolas/genética , Genoma de Planta/genética , Automação , Variação Genética , Fenótipo , Melhoramento Vegetal/métodos , Análise de Sequência de DNARESUMO
Plant nucleotide-binding leucine-rich repeat receptors (NLRs) act as intracellular sensors for pathogen-derived effector proteins and trigger an immune response, frequently resulting in the hypersensitive cell death response (HR) of the infected host cell. The wheat (Triticum aestivum) NLR Pm2 confers resistance against the fungal pathogen Blumeria graminis f. sp. tritici (Bgt) if the isolate contains the specific RNase-like effector AvrPm2. We identified and isolated seven new Pm2 alleles (Pm2e-i) in the wheat D-genome ancestor Aegilops tauschii and two new natural AvrPm2 haplotypes from Bgt. Upon transient co-expression in Nicotiana benthamiana, we observed a variant-specific HR of the Pm2 variants Pm2a and Pm2i towards AvrPm2 or its homolog from the AvrPm2 effector family, BgtE-5843, respectively. Through the introduction of naturally occurring non-synonymous single nucleotide polymorphisms and structure-guided mutations, we identified single amino acids in both the wheat NLR Pm2 and the fungal effector proteins AvrPm2 and BgtE-5843 responsible for the variant-specific HR of the Pm2 variants. Exchanging these amino acids led to a modified HR of the Pm2-AvrPm2 interaction and allowed the identification of the effector head epitope, a 20-amino-acid long unit of AvrPm2 involved in the HR. Swapping of the AvrPm2 head epitope to the non-HR-triggering AvrPm2 family member BgtE-5846 led to gain of a HR by Pm2a. Our study presents a molecular approach to identify crucial effector surface structures involved in the HR and demonstrates that natural and induced diversity in an immune receptor and its corresponding effectors can provide the basis for understanding and modifying NLR-effector specificity.
Assuntos
Aegilops/genética , Ascomicetos/genética , Proteínas Fúngicas/metabolismo , Proteínas NLR/metabolismo , Doenças das Plantas/imunologia , Proteínas de Plantas/metabolismo , Triticum/genética , Alelos , Aminoácidos/metabolismo , Ascomicetos/fisiologia , Resistência à Doença , Proteínas Fúngicas/genética , Variação Genética , Interações Hospedeiro-Patógeno , Mutação , Proteínas NLR/genética , Doenças das Plantas/microbiologia , Imunidade Vegetal , Proteínas de Plantas/genética , Nicotiana/genética , Nicotiana/fisiologia , Triticum/imunologia , Triticum/microbiologiaRESUMO
BACKGROUND: Nucleotide-binding and leucine-rich repeat (NLR) genes have attracted wide attention due to their crucial role in protecting plants from pathogens. SMRT-RenSeq, combining PacBio sequencing after resistance gene enrichment sequencing (RenSeq), is a powerful method for selectively capturing and sequencing full-length NLRs. Haynaldia villosa, a wild grass species with a proven potential for wheat improvement, confers resistance to multiple diseases. So, genome-wide identification of the NLR gene family in Haynaldia villosa by SMRT-RenSeq can facilitate disease resistance genes exploration. RESULTS: In this study, SMRT-RenSeq was performed to identify the genome-wide NLR complement of H. villosa. In total, 1320 NLRs were annotated in 1169 contigs, including 772 complete NLRs. All the complete NLRs were phylogenetically analyzed and 11 main clades with special characteristics were derived. NLRs could be captured with high efficiency when aligned with cloned R genes, and cluster expansion in some specific gene loci was observed. The physical location of NLRs to individual chromosomes in H. villosa showed a perfect homoeologous relationship with group 1, 2, 3, 5 and 6 of other Triticeae species, however, NLRs physically located on 4VL were largely in silico predicted to be located on the homoeologous group 7. Fifteen types of integrated domains (IDs) were integrated in 52 NLRs, and Kelch and B3 NLR-IDs were found to have expanded in H. villosa, while DUF948, NAM-associated and PRT_C were detected as unique integrated domains implying the new emergence of NLR-IDs after H. villosa diverged from other species. CONCLUSION: SMRT-RenSeq is a powerful tool to identify NLR genes from wild species using the baits of the evolutionary related species with reference sequences. The availability of the NLRs from H. villosa provide a valuable library for R gene mining and transfer of disease resistance into wheat.
Assuntos
Resistência à Doença , Proteínas NLR , Doenças das Plantas , Proteínas de Plantas/genética , Poaceae , Resistência à Doença/genética , Família Multigênica , Proteínas NLR/genética , Filogenia , Doenças das Plantas/genética , Poaceae/genética , TriticumRESUMO
A resistance gene atlas is an integral component of the breeder's arsenal in the fight against evolving pathogens. Thanks to high-throughput sequencing, catalogues of resistance genes can be assembled even in crop species with large and polyploid genomes. Here, we report on capture sequencing and assembly of resistance gene homologs in a diversity panel of 907 winter wheat genotypes comprising ex situ genebank accessions and current elite cultivars. In addition, we use accurate long-read sequencing and chromosome conformation capture sequencing to construct a chromosome-scale genome sequence assembly of cv. Attraktion, an elite variety representative of European winter wheat. We illustrate the value of our resource for breeders and geneticists by (i) comparing the resistance gene complements in plant genetic resources and elite varieties and (ii) conducting genome-wide associations scans (GWAS) for the fungal diseases yellow rust and leaf rust using reference-based and reference-free GWAS approaches. The gene content under GWAS peaks was scrutinized in the assembly of cv. Attraktion.
Assuntos
Basidiomycota , Triticum , Basidiomycota/genética , Mapeamento Cromossômico , Cromossomos , Resistência à Doença/genética , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Polimorfismo de Nucleotídeo Único , Locos de Características Quantitativas , Triticum/genética , Triticum/microbiologiaRESUMO
KEY MESSAGE: Stripe rust resistance gene YrAet672 from Aegilops tauschii accession CPI110672 encodes a nucleotide-binding and leucine-rich repeat domain containing protein similar to YrAS2388 and both these members were haplotypes of Yr28. New sources of host resistance are required to counter the continued emergence of new pathotypes of the wheat stripe rust pathogen Puccinia striiformis Westend. f. sp. tritici Erikss. (Pst). Here, we show that CPI110672, an Aegilops tauschii accession from Turkmenistan, carries a single Pst resistance gene, YrAet672, that is effective against multiple Pst pathotypes, including the four predominant Pst lineages present in Australia. The YRAet672 locus was fine mapped to the short arm of chromosome 4D, and a nucleotide-binding and leucine-rich repeat gene was identified at the locus. A transgene encoding the YrAet672 genomic sequence, but lacking a copy of a duplicated sequence present in the 3' UTR, was transformed into wheat cultivar Fielder and Avocet S. This transgene conferred a weak resistance response, suggesting that the duplicated 3' UTR region was essential for function. Subsequent analyses demonstrated that YrAet672 is the same as two other Pst resistance genes described in Ae. tauschii, namely YrAS2388 and Yr28. They were identified as haplotypes encoding identical protein sequences but are polymorphic in non-translated regions of the gene. Suppression of resistance conferred by YrAet672 and Yr28 in synthetic hexaploid wheat lines (AABBDD) involving Langdon (AABB) as the tetraploid parent was associated with a reduction in transcript accumulation.
Assuntos
Aegilops , Basidiomycota , Aegilops/genética , Resistência à Doença/genética , Doenças das Plantas/genética , Mapeamento Cromossômico , Leucina/genética , Genes de Plantas , Basidiomycota/fisiologia , Poaceae/genética , NucleotídeosRESUMO
In the last 20 years, stem rust caused by the fungus Puccinia graminis f. sp. tritici (Pgt), has re-emerged as a major threat to wheat and barley production in Africa and Europe. In contrast to wheat with 60 designated stem rust (Sr) resistance genes, barley's genetic variation for stem rust resistance is very narrow with only ten resistance genes genetically identified. Of these, only one complex locus consisting of three genes is effective against TTKSK, a widely virulent Pgt race of the Ug99 tribe which emerged in Uganda in 1999 and has since spread to much of East Africa and parts of the Middle East. The objective of this study was to assess the functionality, in barley, of cloned wheat Sr genes effective against race TTKSK. Sr22, Sr33, Sr35 and Sr45 were transformed into barley cv. Golden Promise using Agrobacterium-mediated transformation. All four genes were found to confer effective stem rust resistance. The barley transgenics remained susceptible to the barley leaf rust pathogen Puccinia hordei, indicating that the resistance conferred by these wheat Sr genes was specific for Pgt. Furthermore, these transgenic plants did not display significant adverse agronomic effects in the absence of disease. Cloned Sr genes from wheat are therefore a potential source of resistance against wheat stem rust in barley.
Assuntos
Basidiomycota , Resistência à Doença/genética , Hordeum , Doenças das Plantas/genética , Hordeum/genética , Doenças das Plantas/microbiologiaRESUMO
Disease resistance genes encoding nucleotide-binding and leucine-rich repeat (NLR) intracellular immune receptor proteins detect pathogens by the presence of pathogen effectors. Plant genomes typically contain hundreds of NLR-encoding genes. The availability of the hexaploid wheat (Triticum aestivum) cultivar Chinese Spring reference genome allows a detailed study of its NLR complement. However, low NLR expression and high intrafamily sequence homology hinder their accurate annotation. Here, we developed NLR-Annotator, a software tool for in silico NLR identification independent of transcript support. Although developed for wheat, we demonstrate the universal applicability of NLR-Annotator across diverse plant taxa. We applied our tool to wheat and combined it with a transcript-validated subset of genes from the reference gene annotation to characterize the structure, phylogeny, and expression profile of the NLR gene family. We detected 3,400 full-length NLR loci, of which 1,560 were confirmed as expressed genes with intact open reading frames. NLRs with integrated domains mostly group in specific subclades. Members of another subclade predominantly locate in close physical proximity to NLRs carrying integrated domains, suggesting a paired helper function. Most NLRs (88%) display low basal expression (in the lower 10 percentile of transcripts). In young leaves subjected to biotic stress, we found up-regulation of 266 of the NLRs To illustrate the utility of our tool for the positional cloning of resistance genes, we estimated the number of NLR genes within the intervals of mapped rust resistance genes. Our study will support the identification of functional resistance genes in wheat to accelerate the breeding and engineering of disease-resistant varieties.
Assuntos
Software , Resistência à Doença , Genoma de Planta/genética , Filogenia , Doenças das Plantas/microbiologia , Proteínas de Plantas/genética , Triticum/metabolismo , Triticum/microbiologiaRESUMO
Aegilops tauschii, the progenitor of the wheat D genome, contains extensive diversity for biotic and abiotic resistance. Lr21 is a leaf rust resistance gene, which did not enter the initial gene flow from Ae. tauschii into hexaploid wheat due to restrictive hybridization events. Here, we used population genetics and high-resolution comparative genomics to study evolutionary and functional divergence of Lr21 in diploid and hexaploid wheats. Population genetics identified the original Lr21, lr21-1 and lr21-2 alleles and their evolutionary history among Ae. tauschii accessions. Comparative genetics of Lr21 variants between Ae. tauschii and cultivated genotypes suggested at least two independent polyploidization events in bread wheat evolution. Further, a recent re-birth of a unique Lr21-tbk allele and its neofunctionalization was discovered in the hexaploid wheat cv. Tobak. Altogether, four independent alleles were investigated and validated for leaf rust resistance in diploid, synthetic hexaploid and cultivated wheat backgrounds. Besides seedling resistance, we uncover a new role of the Lr21 gene in conferring an adult plant field resistance. Seedling and adult plant resistance turned out to be correlated with developmentally dependent variation in Lr21 expression. Our results contribute to understand Lr21 evolution and its role in establishing a broad-spectrum leaf rust resistance in wheat.
Assuntos
Aegilops/genética , Evolução Molecular , Genes de Plantas , Doenças das Plantas/genética , Resistência à Doença/genética , Hormônio do Crescimento Humano , Doenças das Plantas/microbiologiaRESUMO
In the last 20 years, severe wheat stem rust outbreaks have been recorded in Africa, Europe, and Central Asia. This previously well controlled disease, caused by the fungus Puccinia graminis f. sp. tritici, has reemerged as a major threat to wheat cultivation. The stem rust (Sr) resistance gene Sr22 encodes a nucleotide-binding and leucine-rich repeat receptor which confers resistance to the highly virulent African stem rust isolate Ug99. Here, we show that the Sr22 gene is conserved among grasses in the Triticeae and Poeae lineages. Triticeae species contain syntenic loci with single-copy orthologs of Sr22 on chromosome 7, except Hordeum vulgare, which has experienced major expansions and rearrangements at the locus. We also describe 14 Sr22 sequence variants obtained from both Triticum boeoticum and the domesticated form of this species, T. monococcum, which have been postulated to encode both functional and nonfunctional Sr22 alleles. The nucleotide sequence analysis of these alleles identified historical sequence exchange resulting from recombination or gene conversion, including breakpoints within codons, which expanded the coding potential at these positions by introduction of nonsynonymous substitutions. Three Sr22 alleles were transformed into wheat cultivar Fielder and two postulated resistant alleles from Schomburgk (hexaploid wheat introgressed with T. boeoticum segment carrying Sr22) and T. monococcum accession PI190945, respectively, conferred resistance to P. graminis f. sp. tritici race TTKSK, thereby unequivocally confirming Sr22 effectiveness against Ug99. The third allele from accession PI573523, previously believed to confer susceptibility, was confirmed as nonfunctional against Australian P. graminis f. sp. tritici race 98-1,2,3,5,6.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
Assuntos
Basidiomycota/patogenicidade , Resistência à Doença , Doenças das Plantas/genética , Poaceae/genética , Austrália , Mapeamento Cromossômico , Resistência à Doença/genética , Evolução Molecular , Variação Genética , Genômica , Doenças das Plantas/microbiologia , Poaceae/microbiologiaRESUMO
Unraveling and exploiting mechanisms of disease resistance in cereal crops is currently limited by their large repeat-rich genomes and the lack of genetic recombination or cultivar (cv)-specific sequence information. We cloned the first leaf rust resistance gene Rph1 (Rph1 a) from cultivated barley (Hordeum vulgare) using "MutChromSeq," a recently developed molecular genomics tool for the rapid cloning of genes in plants. Marker-trait association in the CI 9214/Stirling doubled haploid population mapped Rph1 to the short arm of chromosome 2H in a physical region of 1.3 megabases relative to the barley cv Morex reference assembly. A sodium azide mutant population in cv Sudan was generated and 10 mutants were confirmed by progeny-testing. Flow-sorted 2H chromosomes from Sudan (wild type) and six of the mutants were sequenced and compared to identify candidate genes for the Rph1 locus. MutChromSeq identified a single gene candidate encoding a coiled-coil nucleotide binding site Leucine-rich repeat (NLR) receptor protein that was altered in three different mutants. Further Sanger sequencing confirmed all three mutations and identified an additional two independent mutations within the same candidate gene. Phylogenetic analysis determined that Rph1 clustered separately from all previously cloned NLRs from the Triticeae and displayed highest sequence similarity (89%) with a homolog of the Arabidopsis (Arabidopsis thaliana) disease resistance protein 1 protein in Triticum urartu In this study we determined the molecular basis for Rph1-mediated resistance in cultivated barley enabling varietal improvement through diagnostic marker design, gene editing, and gene stacking technologies.
Assuntos
Hordeum/fisiologia , Interações Hospedeiro-Patógeno , Proteínas NLR/fisiologia , Mapeamento Cromossômico , Genes de Plantas , Proteínas de Plantas/fisiologia , Análise de Sequência de DNARESUMO
KEY MESSAGE: Novel rust resistance genes LrP and YrP from Ae. peregrina identified on chromosome 5D and the linked markers will aid deployment of these genes in combination with other major/minor genes. Aegilops peregrina, a wild tetraploid relative of wheat with genome constitution UUSS, displays genetic variation for resistance to leaf and stripe (yellow) rust. The wheat Ae. peregrina introgression line, IL pau16058, harbouring leaf and stripe rust resistance, was crossed with wheat cv. WL711 to generate an F2:3 mapping population. Inheritance studies on this population indicated the transfer of dominant co-segregating resistance to leaf and stripe rust. Ethyl methane sulphonate mutagenesis of IL pau16058 identified independent loss-of-function mutants for leaf and stripe rust resistance, indicating that the leaf and stripe rust resistance is controlled by independent genes, herein designated LrP and YrP, respectively. A high-resolution genetic map of LrP and YrP was constructed using the Illumina Infinium iSelect 90K wheat array and resistance gene enrichment sequencing (RenSeq) markers. The map spans 4.19 cM on the distal-most region of the short arm of chromosome 5D, consisting of eight SNP markers and one microsatellite marker. LrP and YrP co-segregated with markers BS00163889 and 5DS44573_snp and was flanked distally by the SNP marker BS00129707 and proximally by 5DS149010, defining a 15.71 Mb region in the RefSeq v1.0 genome assembly.
Assuntos
Aegilops/genética , Resistência à Doença/genética , Doenças das Plantas/genética , Aegilops/microbiologia , Mapeamento Cromossômico , Cromossomos de Plantas , Genoma de Planta , Doenças das Plantas/microbiologiaRESUMO
KEY MESSAGE: We identified two novel wheat stem rust resistance genes, Sr-1644-1Sh and Sr-1644-5Sh in Aegilops sharonensis that are effective against widely virulent African races of the wheat stem rust pathogen. Stem rust is one of the most important diseases of wheat in the world. When single stem rust resistance (Sr) genes are deployed in wheat, they are often rapidly overcome by the pathogen. To this end, we initiated a search for novel sources of resistance in diverse wheat relatives and identified the wild goatgrass species Aegilops sharonesis (Sharon goatgrass) as a rich reservoir of resistance to wheat stem rust. The objectives of this study were to discover and map novel Sr genes in Ae. sharonensis and to explore the possibility of identifying new Sr genes by genome-wide association study (GWAS). We developed two biparental populations between resistant and susceptible accessions of Ae. sharonensis and performed QTL and linkage analysis. In an F6 recombinant inbred line and an F2 population, two genes were identified that mapped to the short arm of chromosome 1Ssh, designated as Sr-1644-1Sh, and the long arm of chromosome 5Ssh, designated as Sr-1644-5Sh. The gene Sr-1644-1Sh confers a high level of resistance to race TTKSK (a member of the Ug99 race group), while the gene Sr-1644-5Sh conditions strong resistance to TRTTF, another widely virulent race found in Yemen. Additionally, GWAS was conducted on 125 diverse Ae. sharonensis accessions for stem rust resistance. The gene Sr-1644-1Sh was detected by GWAS, while Sr-1644-5Sh was not detected, indicating that the effectiveness of GWAS might be affected by marker density, population structure, low allele frequency and other factors.
Assuntos
Resistência à Doença/genética , Genes de Plantas , Doenças das Plantas/genética , Poaceae/genética , Basidiomycota , Mapeamento Cromossômico , Estudos de Associação Genética , Ligação Genética , Modelos Lineares , Desequilíbrio de Ligação , Modelos Genéticos , Fenótipo , Doenças das Plantas/microbiologia , Poaceae/microbiologia , Locos de Características QuantitativasRESUMO
Transgenerational epigenetic inheritance has been defined by the study of relatively few loci. We examined a population of recombinant inbred lines with epigenetically mosaic chromosomes consisting of wild-type and CG methylation-depleted segments (epiRILs). Surprisingly, transposons that were immobile in the parental lines displayed stochastic movement in 28% of the epiRILs. Although analysis after eight generations of inbreeding, supported by genome-wide DNA methylation profiling, identified recombined parental chromosomal segments, these were interspersed with unexpectedly high frequencies of nonparental methylation polymorphism. Hence, epigenetic inheritance in hybrids derived from parents with divergent epigenomes permits long-lasting epi-allelic interactions that violate Mendelian expectations. Such persistently "unstable" epigenetic states complicate linkage-based epigenomic mapping. Thus, future epigenomic analyses should consider possible genetic instabilities and alternative mapping strategies.
Assuntos
Arabidopsis/genética , Arabidopsis/metabolismo , Metilação de DNA/genética , Elementos de DNA Transponíveis/genética , Epigênese Genética/genética , Genoma de Planta/genética , Instabilidade Genômica/genética , Proteínas de Arabidopsis/genética , Mapeamento Cromossômico , Cromossomos de Plantas/genética , DNA (Citosina-5-)-Metiltransferases/genética , Genes de Plantas/genética , Endogamia , Mosaicismo , Fenótipo , Recombinação GenéticaRESUMO
MOTIVATION: The repetitive nature of plant disease resistance genes encoding for nucleotide-binding leucine-rich repeat (NLR) proteins hampers their prediction with standard gene annotation software. Motif alignment and search tool (MAST) has previously been reported as a tool to support annotation of NLR-encoding genes. However, the decision if a motif combination represents an NLR protein was entirely manual. RESULTS: The NLR-parser pipeline is designed to use the MAST output from six-frame translated amino acid sequences and filters for predefined biologically curated motif compositions. Input reads can be derived from, for example, raw long-read sequencing data or contigs and scaffolds coming from plant genome projects. The output is a tab-separated file with information on start and frame of the first NLR specific motif, whether the identified sequence is a TNL or CNL, potentially full or fragmented. In addition, the output of the NB-ARC domain sequence can directly be used for phylogenetic analyses. In comparison to other prediction software, the highly complex NB-ARC domain is described in detail using several individual motifs.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Imunidade Inata/genética , Anotação de Sequência Molecular , Doenças das Plantas/genética , Proteínas/genética , Análise de Sequência de DNA/métodos , Regulação da Expressão Gênica de Plantas , Genoma de Planta , Proteínas de Repetições Ricas em Leucina , Doenças das Plantas/imunologia , Sequências Repetitivas de Aminoácidos/genética , SoftwareRESUMO
Over the past three decades, significant progress has been made in the field of resistance (R) gene cloning. Advances in recombinant DNA technology, genome sequencing, bioinformatics, plant transformation and plant husbandry have facilitated the transition from cloning R genes in model species to crop plants and their wild relatives. To date, researchers have isolated more than 450 R genes that play important roles in plant immunity. The molecular and biochemical mechanisms by which intracellular immune receptors are activated and initiate defense responses are now well understood. These advances present exciting opportunities for engineering disease-resistant crop plants that are protected by genetics rather than pesticides.