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Abstract Background Cabbage (Brassica oleracea L. var. capitata) is an important crop within the Brassica oleracea species and is extensively cultivated worldwide. In recent years, outbreaks of downy mildew caused by Hyaloperonospora parasitica have resulted in substantial losses in cabbage production. Despite this, there have been limited studies on genes associated with resistance to downy mildew in cabbage. Results This study identified sister lines exhibiting significant differences in disease resistance and susceptibility. Using bulked segregant analysis followed by sequencing (BSA-seq) and linkage analysis, the cabbage resistance locus BoDMR2 was accurately mapped to an approximately 300 kb interval on chromosome 7. Among the candidate genes identified, several single nucleotide polymorphisms (SNPs) and a 3-bp insertion were found within the conserved domain of the Bo7g117810 gene, encoding a leucine-rich repeat domain protein, in susceptible genotypes. Additionally, real-time quantitative polymerase chain reaction (RT‒qPCR) analysis revealed that the expression level of Bo7g117810 in resistant specimens was 2.5-fold higher than that in susceptible specimens. An insertion‒deletion (InDel) marker was designed based on the identified insertion in susceptible materials, facilitating the identification and selection of downy mildew-resistant cabbage cultivars. Conclusions This study identifies Bo7g117810 as a potential candidate gene associated with adult-stage resistance to downy mildew in cabbage, supported by observed differences in gene sequence and expression levels. Furthermore, the development of an InDel marker I1-3, based on its mutation, provides valuable resources for breeding resistant cabbage cultivars.

Background: Cabbage (Brassica oleracea L. var. capitata) is an important crop within the Brassica oleracea species and is extensively cultivated worldwide. In recent years, outbreaks of downy mildew caused by Hyaloperonospora parasitica have resulted in substantial losses in cabbage production. Despite this, there have been limited studies on genes associated with resistance to downy mildew in cabbage. Results: This study identified sister lines exhibiting significant differences in disease resistance and susceptibility. Using bulked segregant analysis followed by sequencing (BSA-seq) and linkage analysis, the cabbage resistance locus BoDMR2 was accurately mapped to an approximately 300 kb interval on chromosome 7. Among the candidate genes identified, several single nucleotide polymorphisms (SNPs) and a 3-bp insertion were found within the conserved domain of the Bo7g117810 gene, encoding a leucine-rich repeat domain protein, in susceptible genotypes. Additionally, real-time quantitative polymerase chain reaction (RT‒qPCR) analysis revealed that the expression level of Bo7g117810 in resistant specimens was 2.5-fold higher than that in susceptible specimens. An insertion‒deletion (InDel) marker was designed based on the identified insertion in susceptible materials, facilitating the identification and selection of downy mildew-resistant cabbage cultivars. Conclusions: This study identifies Bo7g117810 as a potential candidate gene associated with adult-stage resistance to downy mildew in cabbage, supported by observed differences in gene sequence and expression levels. Furthermore, the development of an InDel marker I1-3, based on its mutation, provides valuable resources for breeding resistant cabbage cultivars. [ABSTRACT FROM AUTHOR]

Introduction: Crocus sativus L. has an important medicinal and economic value in traditional perennial Chinese medicine. However, due to its unique growth characteristics, during cultivation it is highly susceptible to disease. The absence of effective resistance genes restricts us to breed new resistant varieties of C. sativus. Methods: In present study, comprehensive transcriptome sequencing was introduced to explore the disease resistance of the candidate gene in healthy and corm rot-infected C. sativus. Results and Discussion: Totally, 43.72 Gb of clean data was obtained from the assembly to generate 65,337 unigenes. By comparing the gene expression levels, 7,575 differentially expressed genes (DEGs) were primarily screened. A majority of the DEGs were completely in charge of defense and metabolism, and 152 of them were annotated as pathogen recognition genes (PRGs) based on the PGRdb dataset. The expression of some transcription factors including NAC, MYB, and WRKY members, changed significantly based on the dataset of transcriptome sequencing. Therefore, this study provides us some valuable information for exploring candidate genes involved in the disease resistance in C. sativus. [ABSTRACT FROM AUTHOR]

Wheat dwarf bunt is a damaging disease caused by Tilletia controversa Kühn (TCK). Once the disease infects wheat, it is difficult to control and will significantly reduce wheat output and quality. RNA sequencing and whole genome re-sequencing were used to search for potential TCK resistance genes in Yili 053 (sensitive variety) and Zhongmai 175 (moderately resistant variety) in the mid-filling, late-filling, and maturity stages. The transcriptomic analysis revealed 11 potential disease resistance genes. An association analysis of the findings from re-sequencing found nine genes with single nucleotide polymorphism mutations. The Kyoto Encyclopedia of Genes and Genomes enrichment analysis showed that three up-regulated genes were involved in the synthesis of benzoxazinone and tryptophan metabolism. Additionally, quantitative real-time polymerase chain reaction confirmed the RNA sequencing results. The results revealed novel TCK resistance genes and provide a theoretical basis for researching the function of resistance genes and molecular breeding. [ABSTRACT FROM AUTHOR]

Southern corn rust (SCR) caused by Puccinia polysora Underw is a major disease leading to severe yield losses in China Summer Corn Belt. Using six multi-locus GWAS methods, we identified a set of SCR resistance QTNs from a diversity panel of 140 inbred lines collected from China Summer Corn Belt. Thirteen QTNs on chromosomes 1, 2, 4, 5, 6, and 8 were grouped into three types of allele effects and their associations with SCR phenotypes were verified by post-GWAS case-control sampling, allele/haplotype effect analysis. Relative resistance (RRR) and relative susceptibility (RRs) catering to its inbred carrier were estimated from single QTN and QTN-QTN combos and epistatitic effects were estimated for QTN-QTN combos. By transcriptomic annotation, a set of candidate genes were predicted to be involved in transcriptional regulation (S5_145, Zm00001d01613, transcription factor GTE4), phosphorylation (S8_123, Zm00001d010672, Pgk2-phosphoglycerate kinase 2), and temperature stress response (S6_164a/S6_164b, Zm00001d038806, hsp101, and S5_211, Zm00001d017978, cellulase25). The breeding implications of the above findings were discussed. [ABSTRACT FROM AUTHOR]

Frogeye leaf spot is a yield-reducing disease of soybean caused by the pathogen Cercospora sojina. Rcs3 has provided durable resistance to all known races of C. sojina since its discovery in the cultivar Davis during the 1980s. Using a recombinant inbred line population derived from a cross between Davis and the susceptible cultivar Forrest, Rcs3 was fine-mapped to a 1.15 Mb interval on chromosome 16. This single locus was confirmed by tracing Rcs3 in resistant and susceptible progeny derived from Davis, as well as three near-isogenic lines. Haplotype analysis in the ancestors of Davis indicated that Davis has the same haplotype at the Rcs3 locus as susceptible cultivars in its paternal lineage. On the basis of these results, it is hypothesized that the resistance allele in Davis resulted from a mutation of a susceptibility allele. Tightly linked SNP markers at the Rcs3 locus identified in this research can be used for effective marker-assisted selection. [ABSTRACT FROM AUTHOR]

Mongolian oak (Quercus mongolica Fisch.) is an ecologically and economically important white oak species native to and widespread in the temperate zone of East Asia. Here, we present a chromosome‐scale reference genome assembly of Q. mongolica, a representative white oak species, by combining Illumina and PacBio data with Hi‐C mapping technologies that is the first reference genome created for an Asian oak. Our results showed that the PacBio draft genome size was 809.84 Mb, with a BUSCO complete gene percentage of 92.71%. Hi‐C scaffolding anchored 774.59 Mb contigs (95.65% of draft assembly) onto 12 pseudochromosomes. The contig N50 and scaffold N50 were 2.64 and 66.74 Mb, respectively. Of the 36,553 protein‐coding genes predicted in the study, approximately 95% had functional annotations in public databases. A total of 435.34 Mb (53.75% of the genome) of repetitive sequences were predicted in the assembled genome. Genome evolution analysis showed that Q. mongolica is closely related to Q. robur from Europe, and they shared a common ancestor ~11.8 million years ago (Ma). Gene family evolution analysis of Q. mongolica revealed that the nucleotide‐binding site (NBS)‐encoding gene family related to disease resistance was significantly contracted, whereas the ECERIFERUM 1 (CER1) homologous genes related to cuticular wax biosynthesis was significantly expanded. This pioneering Asian oak genome resource represents an important supplement to the oak genomics community and will improve our understanding of Asian white oak biology and evolution. [ABSTRACT FROM AUTHOR]

Bambusa pervariabilis × Dendrocalamopsis grandis shoot blight caused by Arthrinium phaeospermum is a fungal disease that has affected a large area in China in recent years. However, it is not clear which genes are responsible for the disease resistance of B. pervariabilis × D. grandis. Based on the analysis of transcriptome and proteome data, two genes, CCoAOMT2 and CAD5, which may be involved in disease resistance, were screened. Two gene expression-interfering varieties, COF RNAi and CAD RNAi were successfully obtained using RNAi technology. Quantitative real-time fluorescence (qRT-PCR) results showed that CCoAOMT2 gene, CAD5 gene and seven related genes expression was down-regulated in the transformed varieties. After inoculating pathogen spore suspension, the incidence and disease index of cof-RNAi and cad-RNAi transformed plants increased significantly. At the same time, it was found that the content of total lignin and flavonoids in the two transformed varieties were significantly lower than that of the wild-type. The subcellular localization results showed that both CCoAOMT2 and CAD5 were localized in the nucleus and cytoplasm. The above results confirm that the CCoAOMT2 and CAD5 genes are involved in the resistance of B. pervariabilis × D.grandis to shoot blight through regulating the synthesis of lignin and flavonoids. [ABSTRACT FROM AUTHOR]

Alfalfa (Medicago sativa L.) is a perennial leguminous forage cultivated globally. Fusarium spp.-induced root rot is a chronic and devastating disease affecting alfalfa that occurs in most production fields. Studying the disease resistance regulatory network and investigating the key genes involved in plant–pathogen resistance can provide vital information for breeding alfalfa that are resistant to Fusarium spp. In this study, a resistant and susceptible clonal line of alfalfa was inoculated with Fusarium proliferatum L1 and sampled at 24 h, 48 h, 72 h, and 7 d post-inoculation for RNA-seq analysis. Among the differentially expressed genes (DEGs) detected between the two clonal lines at the four time points after inoculation, approximately 81.8% were detected at 24 h and 7 d after inoculation. Many DEGs in the two inoculated clonal lines participated in PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI) mechanisms. In addition, transcription factor families such as bHLH, SBP, AP2, WRKY, and MYB were detected in response to infection. These results are an important supplement to the few existing studies on the resistance regulatory network of alfalfa against Fusarium root rot and will help to understand the evolution of host–pathogen interactions. [ABSTRACT FROM AUTHOR]

High expression of plant nucleotide binding site leucine-rich repeat (NBS-LRR) defense genes is often lethal to plant cells, a phenotype perhaps associated with fitness costs. Plants implement several mechanisms to control the transcript level of NBS-LRR defense genes. As negative transcriptional regulators, diverse miRNAs target NBS-LRRs in eudicots and gymnosperms. To understand the evolutionary benefits of this miRNA-NBS-LRR regulatory system, we investigated the NBS-LRRs of 70 land plants, coupling this analysis with extensive small RNA data. A tight association between the diversity of NBS-LRRs and miRNAs was found. The miRNAs typically target highly duplicated NBS-LRRs In comparison, families of heterogeneous NBS-LRRs were rarely targeted by miRNAs in Poaceae and Brassicaceae genomes. We observed that duplicated NBS-LRRs from different gene families periodically gave birth to new miRNAs. Most of these newly emerged miRNAs target the same conserved, encoded protein motif of NBS-LRRs, consistent with a model of convergent evolution for these miRNAs. By assessing the interactions between miRNAs and NBS-LRRs, we found nucleotide diversity in the wobble position of the codons in the target site drives the diversification of miRNAs. Taken together, we propose a co-evolutionary model of plant NBS-LRRs and miRNAs hypothesizing how plants balance the benefits and costs of NBS-LRR defense genes.

Copyright of Xinjiang Agricultural Sciences is the property of Xinjiang Agricultural Sciences Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Red swamp crayfish (Procambarus clarkii) is an important aquaculture species in China. With increasing crayfish culture, a number of outbreaks of various diseases have been identified in crayfish. Despite this, there are no reports on the application of disease resistance genes in the molecular breeding of crayfish. In this study, transcriptome analysis was performed to explore the disease resistance genes in crayfish, with a focus on investigating the genetic variations in the open reading frames of these genes, for subsequent haplotype analysis. Furthermore, pathogen-challenge experiments were carried out in the crayfish, to identify the favoured haplotypes. A novel disease resistance gene, R (Resistance), was identified by means of transcriptome analysis. In total, two, four, and five haplotypes of the three disease resistance genes, ALF , R , and crustin2 , respectively, were detected. ALF1 , R1 , and Cru1 were the favoured haplotypes of ALF , R , and crustin2 , respectively. Subsequently, the favoured haplotype combinations of the different genes were obtained, and a series of molecular markers were developed to identify them. Finally, we propose a molecular breeding strategy to enhance the disease resistance of crayfish, and thus, improve its production. • A novel disease resistance gene R was identified in red swamp crayfish. • Different haplotypes of crustin2 , ALF , and R were analysed. • The favoured haplotype combinations for disease resistance were identified. • An ideal strategy was proposed for crayfish breeding. [ABSTRACT FROM AUTHOR]

Abstract False smut of rice, an important emerging disease caused by Ustilaginoidea virens, greatly reduces grain yield and deteriorates grain quality in many rice-growing regions worldwide. Identification of quantitative trait loci (QTL) conferring false smut resistance will facilitate incorporation of false smut resistance into elite cultivars. In this study, a set of recombinant inbred lines (RILs) derived from a cross of a resistant rice landrace MR183–2 and a high susceptible line 08R2394 were evaluated to map resistance QTLs for false smut. A total of 179 simple sequence repeat (SSR) polymorphic markers were identified for constructing genetic linkage maps. Using a composite interval mapping method, five false smut resistance QTLs were detected on chromosomes 2, 4, 8 and 11 in the RIL population. Among these QTLs, qFsr8–1 within a small region on chromosome 8 represents a major quantitative locus explaining the greatest phenotypic variance. Gene annotation in this major QTL region provides a theoretical basis for cloning of resistance QTLs. The SSR markers genetically linked to qFsr8–1 are valuable for marker-assisted breeding for false smut resistance in rice. In addition, nine QTLs for heading date were detected in this population. Correlation analysis of disease resistance score and heading date indicates that false smut resistance negatively correlates with the growth period length in rice.

FB_MR5 is a nucleotide-binding domain and leucine-rich repeat protein identified from wild apple species Malus × robusta 5 conferring disease resistance to bacterial fire blight. FB_MR5 (hereafter MrMR5) recognizes the cysteine protease effector EaAvrRpt2 secreted from the causal agent of bacterial fire blight, Erwinia amylovora. We previously reported that MrMR5 is activated by the C-terminal cleavage product (ACP3) of Malus domestica RIN4 (MdRIN4) produced by EaAvrRpt2-directed proteolysis. We show that MbMR5 from a wild apple species Malus baccata shares 99.4% amino acid sequence identity with MrMR5. Surprisingly, transient expression of MbMR5 in Nicotiana benthamiana showed autoactivity in contrast to MrMR5. Domain swap and mutational analyses revealed that 1 amino acid polymorphism in the MbMR5 CC domain is critical in enhancing autoactivity. We further demonstrated that MrMR5 carrying 7 amino acid polymorphisms present in MbMR5 is not activated by MdRIN4 ACP3 but recognizes AvrRpt2 without MdRIN4 in N. benthamiana. Our findings indicate that naturally occurring polymorphisms of MR5 natural variants can confer its cell death-inducing activity and the effector recognition mechanism likely due to altered compatibility with RIN4., Competing Interests: Declaration of Competing Interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The author is an Editorial Board Member/Editor-in-Chief/Associate Editor/Guest Editor for Molecules and Cells and was not involved in the editorial review or the decision to publish this article., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

SUMMARY: Oryza sativa (rice) plays an essential food security role for more than half of the world's population. Obtaining crops with high levels of disease resistance is a major challenge for breeders, especially today, given the urgent need for agriculture to be more sustainable. Plant resistance genes are mainly encoded by three large leucine‐rich repeat (LRR)‐containing receptor (LRR‐CR) families: the LRR‐receptor‐like kinase (LRR‐RLK), LRR‐receptor‐like protein (LRR‐RLP) and nucleotide‐binding LRR receptor (NLR). Using lrrprofiler, a pipeline that we developed to annotate and classify these proteins, we compared three publicly available annotations of the rice Nipponbare reference genome. The extended discrepancies that we observed for LRR‐CR gene models led us to perform an in‐depth manual curation of their annotations while paying special attention to nonsense mutations. We then transferred this manually curated annotation to Kitaake, a cultivar that is closely related to Nipponbare, using an optimized strategy. Here, we discuss the breakthrough achieved by manual curation when comparing genomes and, in addition to 'functional' and 'structural' annotations, we propose that the community adopts this approach, which we call 'comprehensive' annotation. The resulting data are crucial for further studies on the natural variability and evolution of LRR‐CR genes in order to promote their use in breeding future resilient varieties. Significance Statement: The automatic structural annotation of genes evolving through an active birth‐and‐death model, such as LRR‐CRs, is often inconsistent because numerous paralogs accumulate nonsense mutations in their coding sequences. We propose a consensus method of annotating these genes while retaining all sequence fragments that are clearly derived from their ancestral coding sequences. They are then tagged as non‐canonical or canonical, respectively, depending on the presence or absence of nonsense mutations. [ABSTRACT FROM AUTHOR]

Identifying the molecular basis of resistance to pathogens is critical to promote a chemical-free cropping system. In plants, nucleotide-binding leucine-rich repeat constitute the largest family of disease resistance (R) genes, but this resistance can be rapidly overcome by the pathogen, prompting research into alternative sources of resistance. Anthracnose, caused by the fungus Colletotrichum lindemuthianum , is one of the most important diseases of common bean. This study aimed to identify the molecular basis of Co-x , an anthracnose R gene conferring total resistance to the extremely virulent C. lindemuthianum strain 100. To that end, we sequenced the Co-x 58 kb target region in the resistant JaloEEP558 (Co-x) common bean and identified KTR2/3 , an additional gene encoding a truncated and chimeric CRINKLY4 kinase, located within a CRINKLY4 kinase cluster. The presence of KTR2/3 is strictly correlated with resistance to strain 100 in a diversity panel of common beans. Furthermore, KTR2/3 expression is up-regulated 24 hours post-inoculation and its transient expression in a susceptible genotype increases resistance to strain 100. Our results provide evidence that Co-x encodes a truncated and chimeric CRINKLY4 kinase probably resulting from an unequal recombination event that occurred recently in the Andean domesticated gene pool. This atypical R gene may act as a decoy involved in indirect recognition of a fungal effector. [ABSTRACT FROM AUTHOR]

Rice blast is one of the most serious diseases of rice and a major threat to rice production. Breeding disease-resistant rice is one of the most economical, safe, and effective measures for the control of rice blast. As a complement to traditional crop breeding, the transgenic method can avoid the time-consuming process of crosses and multi-generation selection. In this study, maize (Zea mays) Activator (Ac)/Dissociation (Ds) transposon vectors carrying green fluorescent protein (GFP) and red fluorescent protein (mCherry) genetic markers were used for generating marker-free transgenic rice. Double fluorescent protein-aided counterselection against the presence of T-DNA was performed together with polymerase chain reaction (PCR)-based positive selection for the gene of interest (GOI) to screen marker-free progeny. We cloned an RNAi expression cassette of the rice Pi21 gene that negatively regulates resistance to rice blast as a GOI into the Ds element in the Ac/Ds vector and obtained marker-free T1 rice plants from 13 independent transgenic lines. Marker-free and Ds/GOI-homozygous rice lines were verified by PCR and Southern hybridization analysis to be completely free of transgenic markers and T-DNA sequences. qRT-PCR analysis and rice blast disease inoculation confirmed that the marker-free transgenic rice lines exhibited decreased Pi21 expression levels and increased resistance to rice blast. TAIL-PCR results showed that the Ds (Pi21-RNAi) transgenes in two rice lines were reintegrated in intergenic regions in the rice genome. The Ac/Ds vector with dual fluorescent protein markers offers more reliable screening of marker-free transgenic progeny and can be utilized in the transgenic breeding of rice disease resistance and other agronomic traits.

Expression of I Rlm4 i and I Rlm7 i increased substantially in both Topas- I Rlm4 i and Topas- I Rlm7 i in response to infection (Figure 1e). Brassica napus genes Rlm4 and Rlm7, conferring resistance to Leptosphaeria maculans, are alleles of the Rlm9 wall-associated kinase-like resistance locus The Rlm7-1 and Rlm7-2 proteins differ from Rlm4 in conserved amino acids in the putative extracellular ligand-binding domains, at positions 60, 64 (WAK GUB), and 283 (WAK), which may explain the variation in recognition specificity between Rlm4 and Rlm7 towards AvrLm7. [Extracted from the article]

Rice blast is one of the most serious diseases of rice and a major threat to rice production. Breeding disease-resistant rice is one of the most economical, safe, and effective measures for the control of rice blast. As a complement to traditional crop breeding, the transgenic method can avoid the time-consuming process of crosses and multi-generation selection. In this study, maize (Zea mays) Activator (Ac)/Dissociation (Ds) transposon vectors carrying green fluorescent protein (GFP) and red fluorescent protein (mCherry) genetic markers were used for generating marker-free transgenic rice. Double fluorescent protein-aided counterselection against the presence of T-DNA was performed together with polymerase chain reaction (PCR)-based positive selection for the gene of interest (GOI) to screen marker-free progeny. We cloned an RNAi expression cassette of the rice Pi21 gene that negatively regulates resistance to rice blast as a GOI into the Ds element in the Ac/Ds vector and obtained marker-free T1 rice plants from 13 independent transgenic lines. Marker-free and Ds /GOI-homozygous rice lines were verified by PCR and Southern hybridization analysis to be completely free of transgenic markers and T-DNA sequences. qRT-PCR analysis and rice blast disease inoculation confirmed that the marker-free transgenic rice lines exhibited decreased Pi21 expression levels and increased resistance to rice blast. TAIL-PCR results showed that the Ds (Pi21 -RNAi) transgenes in two rice lines were reintegrated in intergenic regions in the rice genome. The Ac/Ds vector with dual fluorescent protein markers offers more reliable screening of marker-free transgenic progeny and can be utilized in the transgenic breeding of rice disease resistance and other agronomic traits. [ABSTRACT FROM AUTHOR]

Disease resistance (R) gene, RPP13, plays an important role in the resistance of plants to pathogen infections; its function in resistance of wheat to powdery mildew remains unknown. In this study, a RNA‐Seq technique was used to monitor expression of genes in susceptible wheat 'Jing411' and resistant near‐isogenic line 'BJ‐1' in response to powdery mildew infection. Overall, 413 differential expression genes were observed and identified as involved in disease resistance. RPP13 homologous gene on wheat chromosome 7D was preliminarily identified using the wheat 660K SNP chip. RPP13 was highly expressed in 'BJ‐1' and encodes 1,027 amino acids, including CC, NB and LRR domain, termed TaRPP13‐3. After inoculation with powdery mildew, expression of TaRPP13‐3 in resistant wheat changed with time, but average expression was higher when compared to susceptible variety, thus indicating that TaRPP13‐3 is involved in resistance to powdery mildew. Virus‐induced gene silencing (VIGS) was used to inhibit expression of TaRPP13‐3 in resistant parent 'Brock'. Results indicated that silencing of TaRPP13‐3 led to decreased disease resistance in 'Brock'. Overall results of this study indicate that TaRPP13‐3 gene is involved in the defence response of wheat to powdery mildew and plays a positive role in wheat powdery mildew interactions. [ABSTRACT FROM AUTHOR]

Plants often use nucleotide-binding leucine-rich repeats (NLRs) to recognize specific virulence proteins and activate the hypersensitive response thereby defending against invaders. However, data on NLRs and the resistance mechanism of NLR protein mediation in tea plant are extremely limited. In this study, 400 and 303 CsNLRs were identified from the genomes of C. sinensis var. sinensis (CSS) and C. sinensis var. assamica (CSA), respectively. Phylogenetic analysis revealed that the numbers in CNL groups are predominant in both CSS and CSA. RNA-Seq revealed that the expression of CsNLRs is induced by Colletotrichum fructicola , cold, drought, salt stress and exogenous methyl jasmonate. The 21 CsCNLs that are highly expressed in tea plant under biotic and abiotic stresses as well as during bud dormancy and in different tissues are identified. Gene structure analysis revealed several cis -regulatory elements associated with phytohormones and light responsiveness in the promoter regions of these 21 CsCNLs. • NLR family gene of tea plants were identified. • CNL was the predominant type in tea plant NLR family. • NLR genes in tea plant were not only induced by biotic and abiotic stresses, but also were involved in tea plant growth. [ABSTRACT FROM AUTHOR]

Key message: Two large-effect QTLs and 14 candidate genes conferring resistance to Marssonina leaf spot disease were identified in an F1Populus deltoides pedigree, which provided valuable information for cloning the particular underlying genes in future. Marssonina leaf spot disease (MLSD), which is caused by Marssonina brunnea, is a devastating threat to poplar plantations. To map quantitative trait loci (QTLs) underlying resistance to MLSD, an F1P. deltoides pedigree has been established and genetic maps were constructed for the mapping parents according to the two-way pseudo-testcross mapping strategy. The female map contained 913 markers spanning a total genetic distance of 3132 cM, with linkage groups (LGs) corresponding to the 19 haploid chromosomes in poplar, whereas the paternal map contained 252 markers distributed on 22 LGs and covered a genetic length of 1809 cM. The established maps were further aligned to the poplar consensus genetic map based on the integrated SSR markers. The resistance to MLSD was recorded as a complex binary trait based on the black spot symptom on leaves. Analyses of QTLs revealed two large-effect QTLs in LGs VI and XVI, namely qMLSD-VI-1 and qMLSD-XVI-2, which explained 50.3% and 34.5% of the total phenotypic variance, respectively. A significant interaction between these two QTLs was detected based on a two-way ANOVA. In this mapping pedigree, the female parent contributed all of the QTL alleles conferring resistance to M. brunnea. Genome sequences in the target regions were obtained by aligning the QTL intervals to the poplar genome sequence with the mapped SSR markers. The importance and utility of the 14 candidate genes associated with disease resistance identified in the QTL intervals should be more thoroughly characterized in future studies. [ABSTRACT FROM AUTHOR]

Plant disease resistance (R) genes have undergone significant evolutionary divergence to cope with rapid changes in pathogens. These highly variable evolutionary patterns may have contributed to diversity in R gene protein families or structures. Here, the evolutionary patterns of 76 identified R genes and their homologs were investigated within and between plant species. Results demonstrated that nucleotide binding sites and leucine-rich-repeat genes located in loci with complex evolutionary histories tended to evolve rapidly, have high variation in copy numbers, exhibit high levels of nucleotide variation and frequent gene conversion events, and also exhibit high non-synonymous to synonymous substitution ratios in LRR regions. However, non-NBS-LRR R genes are relatively well conserved with constrained variation and are more likely to participate in the basic defense system of hosts. In addition, both conserved and highly divergent evolutionary patterns were observed for the same R genes and were consistent with inter- and intra-specific distributions of some R genes. These results thus indicate either continuous or altered evolutionary patterns between and within species. The present investigation is the first attempt to investigate evolutionary patterns among all clearly functional R genes. The results reported here thus provide a foundation for future plant disease studies. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Downy mildew (DM) resistance is a highly desirable agronomic trait in grape breeding. High variation in Plasmopara viticola resistance was found in Vitis cultivars. Some accessions show high P. viticola resistance even under conditions highly conducive to DM. Here, leaf disc inoculation experiments revealed that Vitis amurensis 'Zuoshaner' exhibited DM resistance with necrotic spots, whereas the V. amurensis × V. vinifera hybrid cultivar 'Zuoyouhong' was susceptible. Changes in plant hormones accumulation profiles differed between the cultivars. To investigate the genetic mechanisms related to DM resistance, we performed genome-wide sequencing of 'Zuoshaner' and 'Zuoyouhong' and identified cultivar-specific single-nucleotide polymorphisms, insertions/deletions (indels), structural variations (SVs), and copy number variations (CNVs), identifying 5399 SVs and 191 CNVs specific for 'Zuoshaner'. Genes affected by these genetic variations were enriched in biological processes, including defense response and response to stress and stimulation, and were associated with sesquiterpenoid and triterpenoid biosynthesis, ABC transporters, and phenylalanine metabolism pathways. Additionally, indels and SVs were detected in six NBS-LRR disease resistance genes, and a CNV was mapped to the Rpv8 locus responsible for downy mildew resistance. These findings further our understanding of the genetic mechanisms underlying grape mildew resistance, and will facilitate genomic marker-assisted breeding for improved V. amurensis cultivars. [ABSTRACT FROM AUTHOR]

The tomato Pto gene encodes a serine/threonine kinase (STK) whose molecular characterization provides valuable insights into the disease resistance mechanism of tomato and it is considered as a promising candidate for engineering broad-spectrum pathogen resistance in this crop. In this study, a pair of degenerate primers based on conserved subdomains of plant STKs similar to the tomato Pto protein were used to amplify similar sequences in Hevea brasiliensis. A fragment of -550 bp was amplified, cloned and sequenced. The sequence analysis of several clones revealed twelve distinct sequences were highly similar to STKs. Based on their significant similarity with the tomato Pto protein (BLASTX E value <3e-53), seven of them were classified as Pto resistance gene candidates (Pto-RGCs). Multiple sequence alignment of the hevea Pto-RGC products revealed that these sequences contained several conserved subdomains in most STKs and also several conserved residues that are crucial for Pto function. Moreover, the phylogenetic analysis showed that the hevea Pto-RGCs were clustered with Pto suggesting a common evolutionary origin with this R gene. The Pto-RGCs isolated in this study represent a valuable sequence resource that could assist in the development of disease resistance in hevea. [ABSTRACT FROM AUTHOR]

Roots are vital to plant survival and crop yield, yet few efforts have been made to characterize the expressed genes in the roots of non-model plants (root transcriptomes). This study was conducted to sequence, assemble, annotate, and characterize the root transcriptomes of three caladium cultivars (Caladium × hortulanum) using RNA-Seq. The caladium cultivars used in this study have different levels of resistance to Pythium myriotylum, the most damaging necrotrophic pathogen to caladium roots. Forty-six to 61 million clean reads were obtained for each caladium root transcriptome. De novo assembly of the reads resulted in approximately 130,000 unigenes. Based on bioinformatic analysis, 71,825 (52.3%) caladium unigenes were annotated for putative functions, 48,417 (67.4%) and 31,417 (72.7%) were assigned to Gene Ontology (GO) and Clusters of Orthologous Groups (COG), respectively, and 46,406 (64.6%) unigenes were assigned to 128 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. A total of 4518 distinct unigenes were observed only in Pythium-resistant “Candidum” roots, of which 98 seemed to be involved in disease resistance and defense responses. In addition, 28,837 simple sequence repeat sites and 44,628 single nucleotide polymorphism sites were identified among the three caladium cultivars. These root transcriptome data will be valuable for further genetic improvement of caladium and related aroids. [ABSTRACT FROM AUTHOR]

A large set of candidate nucleotide-binding site (NBS)-encoding genes related to disease resistance was identified in the sorghum (Sorghum bicolor) genome. These resistance (R) genes were characterized based on their structural diversity, physical chromosomal location and phylogenetic relationships. Based on their N-terminal motifs and leucine-rich repeats (LRR), 50 non-regular NBS genes and 224 regular NBS genes were identified in 274 candidate NBS genes. The regular NBS genes were classified into ten types: CNL, CN, CNLX, CNX, CNXL, CXN, NX, N, NL and NLX. The vast majority (97%) of NBS genes occurred in gene clusters, indicating extensive gene duplication in the evolution of S. bicolor NBS genes. Analysis of the S. bicolor NBS phylogenetic tree revealed two major clades. Most NBS genes were located at the distal tip of the long arms of the ten sorghum chromosomes, a pattern significantly different from rice and Arabidopsis, the NBS genes of which have a random chromosomal distribution.

High expression of plant nucleotide binding site leucine-rich repeat (NBS-LRR) defense genes is often lethal to plant cells, a phenotype perhaps associated with fitness costs. Plants implement several mechanisms to control the transcript level of NBS-LRR defense genes. As negative transcriptional regulators, diverse miRNAs target NBS-LRRs in eudicots and gymnosperms. To understand the evolutionary benefits of this miRNA-NBS-LRR regulatory system, we investigated the NBS-LRRs of 70 land plants, coupling this analysis with extensive small RNA data. A tight association between the diversity of NBSLRRs and miRNAs was found. The miRNAs typically target highly duplicated NBS-LRRs. In comparison, families of heterogeneous NBS-LRRs were rarely targeted by miRNAs in Poaceae and Brassicaceae genomes. We observed that duplicated NBS-LRRs from different gene families periodically gave birth to new miRNAs. Most of these newly emerged miRNAs target the same conserved, encoded protein motif of NBS-LRRs, consistent with a model of convergent evolution for these miRNAs. By assessing the interactions betweenmiRNAs and NBS-LRRs, we found nucleotide diversity in the wobble position of the codons in the target site drives the diversification ofmiRNAs. Taken together, we propose a co-evolutionarymodel of plant NBS-LRRs and miRNAs hypothesizing how plants balance the benefits and costs of NBS-LRR defense genes. [ABSTRACT FROM AUTHOR]

Key message : The potato late blight resistance gene R8 has been cloned. R8 is found in five late blight resistant varieties deployed in three different continents. R8 recognises Avr8 and is homologous to the NB-LRR protein Sw-5 from tomato. Abstract: The broad spectrum late blight resistance gene R8 from Solanum demissum was cloned based on a previously published coarse map position on the lower arm of chromosome IX. Fine mapping in a recombinant population and bacterial artificial chromosome (BAC) library screening resulted in a BAC contig spanning 170 kb of the R8 haplotype. Sequencing revealed a cluster of at least ten R gene analogues (RGAs). The seven RGAs in the genetic window were subcloned for complementation analysis. Only one RGA provided late blight resistance and caused recognition of Avr8. From these results, it was concluded that the newly cloned resistance gene was indeed R8. R8 encodes a typical intracellular immune receptor with an N-terminal coiled coil, a central nucleotide binding site and 13 C-terminal leucine rich repeats. Phylogenetic analysis of a set of representative Solanaceae R proteins shows that R8 resides in a clearly distinct clade together with the Sw-5 tospovirus R protein from tomato. It was found that the R8 gene is present in late blight resistant potato varieties from Europe (Sarpo Mira), USA (Jacqueline Lee, Missaukee) and China (PB-06, S-60). Indeed, when tested under field conditions, R8 transgenic potato plants showed broad spectrum resistance to the current late blight population in the Netherlands, similar to Sarpo Mira. [ABSTRACT FROM AUTHOR]

Two classes of genes are used for breeding rust resistant wheat. The first class, called R (for resistance) genes, are pathogen race-specific in their action, effective at all plant growth stages and probably mostly encode immune receptors of the nucleotide binding leucine rich repeat (NB-LRR) class. The second class called Adult Plant Resistance genes (APR) because resistance is usually functional only in adult plants, and, in contrast to most R genes, the levels of resistance conferred by single APR genes are only partial and allow considerable disease development. Some but not all APR genes provide resistance to all isolates of a rust pathogen species and a subclass of these provides resistance to several fungal pathogen species. Initial indications are that APR genes encode a more heterogeneous range of proteins than R proteins. Two APR genes, Lr34 and Yr36, have been cloned from wheat and their products are an ABC transporter and a protein kinase, respectively. Lr34 and Sr2 have provided long lasting and widely used (durable) partial resistance and are mainly used in conjunction with other R and APR genes to obtain adequate rust resistance. We caution that some APR genes indeed include race-specific, weak R genes which may be of the NB-LRR class. A research priority to better inform rust resistance breeding is to characterize further APR genes in wheat and to understand how they function and how they interact when multiple APR and R genes are stacked in a single genotype by conventional and GM breeding. An important message is do not be complacent about the general durability of all APR genes.

The nucleotide-binding site (NBS)-leucine-rich repeat (LRR) gene family is crucially important for offering resistance to pathogens. To explore evolutionary conservation and variability of NBS-LRR genes across grass species, we identified 88, 107, 24, and 44 full-length NBS-LRR genes in sorghum, rice, maize, and Brachypodium, respectively. A comprehensive analysis was performed on classification, genome organization, evolution, expression, and regulation of these NBS-LRR genes using sorghum as a representative of grass species. In general, the full-length NBS-LRR genes are highly clustered and duplicated in sorghum genome mainly due to local duplications. NBS-LRR genes have basal expression levels and are highly potentially targeted by miRNA. The number of NBS-LRR genes in the four grass species is positively correlated with the gene clustering rate. The results provided a valuable genomic resource and insights for functional and evolutionary studies of NBS-LRR genes in grass species. [ABSTRACT FROM AUTHOR]

Paulownia witches' broom (PaWB) caused by an obligate biotrophic plant pathogen called phytoplasma, is a devastating disease of paulownia trees over a large part of the world. However, little is known about the molecular mechanisms that underlie phytoplasma pathogenicity in paulownia or about the mode of interactions with host plants. In this study, genome-wide gene expression profiling was used to compare healthy, phytoplasma-infected, and both phytoplasma-infected and 20 mg L methyl methane sulfonate (MMS) treated Paulownia fortunei plants using high-throughput mRNA sequencing analysis. A total of 6571 and 1377 differentially expressed unigenes were identified in the phytoplasma-infected plants versus healthy plants and in 20 mg L MMS-treated plants versus phytoplasma-infected plants, respectively. Expression changes of 16 candidate differentially expressed unigenes were validated by qRT-PCR, indicating significant differences among the three P. fortunei samples. Our analysis showed that dramatic changes occurred in the gene expression profile of P. fortunei after PaWB phytoplasma infection and MMS treatment. The transcription of a large number of genes related to the plant-pathogen interaction, including phenylpropanoid metabolism, hormone biosynthesis and signaling, defense and/or pathogenesis, and signal transduction, were significantly up-regulated in the phytoplasma-infected paulownia and then returned to the levels in the healthy controls after MMS treatment. Our systematic analysis provides comprehensive transcriptomic data about P. fortunei trees infected by PaWB phytoplasma. The findings will help unraveling the molecular mechanisms of plant-phytoplasma interactions and may pave the way for engineering P. fortunei trees with improved properties. [ABSTRACT FROM AUTHOR]