Genetic and transcriptomic dissection of host defense to Goss's bacterial wilt and leaf blight of maize. - Related Documents




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875901.0000Genetic and transcriptomic dissection of host defense to Goss's bacterial wilt and leaf blight of maize. Goss's wilt, caused by the Gram-positive actinobacterium Clavibacter nebraskensis, is an important bacterial disease of maize. The molecular and genetic mechanisms of resistance to the bacterium, or, in general, Gram-positive bacteria causing plant diseases, remain poorly understood. Here, we examined the genetic basis of Goss's wilt through differential gene expression, standard genome-wide association mapping (GWAS), extreme phenotype (XP) GWAS using highly resistant (R) and highly susceptible (S) lines, and quantitative trait locus (QTL) mapping using 3 bi-parental populations, identifying 11 disease association loci. Three loci were validated using near-isogenic lines or recombinant inbred lines. Our analysis indicates that Goss's wilt resistance is highly complex and major resistance genes are not commonly present. RNA sequencing of samples separately pooled from R and S lines with or without bacterial inoculation was performed, enabling identification of common and differential gene responses in R and S lines. Based on expression, in both R and S lines, the photosynthesis pathway was silenced upon infection, while stress-responsive pathways and phytohormone pathways, namely, abscisic acid, auxin, ethylene, jasmonate, and gibberellin, were markedly activated. In addition, 65 genes showed differential responses (up- or down-regulated) to infection in R and S lines. Combining genetic mapping and transcriptional data, individual candidate genes conferring Goss's wilt resistance were identified. Collectively, aspects of the genetic architecture of Goss's wilt resistance were revealed, providing foundational data for mechanistic studies.202337652038
8110.9992Biological control of bacterial wilt in Arabidopsis thaliana involves abscissic acid signalling. Means to control bacterial wilt caused by the phytopathogenic root bacteria Ralstonia solanacearum are limited. Mutants in a large cluster of genes (hrp) involved in the pathogenicity of R. solanacearum were successfully used in a previous study as endophytic biocontrol agents in challenge inoculation experiments on tomato. However, the molecular mechanisms controlling this resistance remained unknown. We developed a protection assay using Arabidopsis thaliana as a model plant and analyzed the events underlying the biological control by genetic, transcriptomic and molecular approaches. High protection rates associated with a significant decrease in the multiplication of R. solanacearum were observed in plants pre-inoculated with a ΔhrpB mutant strain. Neither salicylic acid, nor jasmonic acid/ethylene played a role in the establishment of this resistance. Microarray analysis showed that 26% of the up-regulated genes in protected plants are involved in the biosynthesis and signalling of abscissic acid (ABA). In addition 21% of these genes are constitutively expressed in the irregular xylem cellulose synthase mutants (irx), which present a high level of resistance to R. solanacearum. We propose that inoculation with the ΔhrpB mutant strain generates a hostile environment for subsequent plant colonization by a virulent strain of R. solanacearum.201222432714
878520.9991Mechanism of resistance to Cucumber mosaic virus elicited by inoculation with Bacillus subtilis subsp. subtilis. BACKGROUND: Systemic resistance stimulated by rhizosphere bacteria is an important strategy for the management of plant viruses. The efficacy of Bacillus subtilis subsp. subtilis was assessed for protection of cucumber and Arabidopsis against Cucumber mosaic virus (CMV). Moreover, transcriptomic analysis was carried out for A. thaliana colonized with B. subtilis subsp. subtilis and infected with CMV. RESULTS: Treatment with a cell suspension of Bacillus revealed a significant reduction of CMV severity in comparison to their control. All Arabidopsis mutants treated with B. subtilis showed a clear reduction in CMV accumulation. Disease severity data and virus concentration titer measurements correlated with gene up-regulation in microarray and reverse transcription quantitative polymerase chain reaction (RT-qPCR) experiments. Bacillus treatment increased Arabidopsis growth characteristics (fresh and dry weights and number of leaflets) under pot conditions. The molecular mechanisms by which Bacillus activated resistance to CMV were investigated. Using the microarray hybridization technique, we were able to determine the mechanism of resistance elicited by B. subtilis against CMV. The transcriptomic analysis confirmed the up-regulation of more than 250 defense-related genes in Arabidopsis expressing induced systemic resistance (ISR). RT-qPCR results validated the overexpression of defense genes (YLS9 and PR1 in Arabidopsis and PR1 and LOX in cucumber), implying their important roles in the stimulated defense response. CONCLUSION: Through the study of microarray and RT-qPCR analyses, it can be concluded that the overexpression of pathogenesis-related genes was necessary to stimulate CMV defense in cucumber and Arabidopsis by B. subtilis subsp. subtilis. © 2021 Society of Chemical Industry.202234437749
875830.9991Genome-wide association mapping for resistance to bacterial blight and bacterial leaf streak in rice. Using genome-wide SNP association mapping, a total of 77 and 7 loci were identified for rice bacterial blight and bacterial leaf streak resistance, respectively, which may facilitate rice resistance improvement. Bacterial blight (BB) and bacterial leaf streak (BLS) caused by Gram-negative bacteria Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), respectively, are two economically important diseases negatively affecting rice production. To mine new sources of resistance, a set of rice germplasm collection consisting of 895 re-sequenced accessions from the 3000 Rice Genomes Project (3 K RGP) were screened for BB and BLS resistance under field conditions. Higher levels of BB resistance were observed in aus/boro subgroup, whereas the japonica, temperate japonica and tropical japonica subgroups possessed comparatively high levels of resistance to BLS. A genome-wide association study (GWAS) mined 77 genomic loci significantly associated with BB and 7 with BLS resistance. The phenotypic variance (R(2)) explained by these loci ranged from 0.4 to 30.2%. Among the loci, 7 for BB resistance were co-localized with known BB resistance genes and one for BLS resistance overlapped with a previously reported BLS resistance QTL. A search for the candidates in other novel loci revealed several defense-related genes that may be involved in resistance to BB and BLS. High levels of phenotypic resistance to BB or BLS could be attributed to the accumulation of the resistance (R) alleles at the associated loci, indicating their potential value in rice resistance breeding via gene pyramiding. The GWAS analysis validated the known genes underlying BB and BLS resistance and identified novel loci that could enrich the current resistance gene pool. The resources with strong resistance and significant SNPs identified in this study are potentially useful in breeding for BB and BLS resistance.202133830376
2740.9991In silico comparison of transcript abundances during Arabidopsis thaliana and Glycine max resistance to Fusarium virguliforme. BACKGROUND: Sudden death syndrome (SDS) of soybean (Glycine max L. Merr.) is an economically important disease, caused by the semi-biotrophic fungus Fusarium solani f. sp. glycines, recently renamed Fusarium virguliforme (Fv). Due to the complexity and length of the soybean-Fusarium interaction, the molecular mechanisms underlying plant resistance and susceptibility to the pathogen are not fully understood. F. virguliforme has a very wide host range for the ability to cause root rot and a very narrow host range for the ability to cause a leaf scorch. Arabidopsis thaliana is a host for many types of phytopathogens including bacteria, fungi, viruses and nematodes. Deciphering the variations among transcript abundances (TAs) of functional orthologous genes of soybean and A. thaliana involved in the interaction will provide insights into plant resistance to F. viguliforme. RESULTS: In this study, we reported the analyses of microarrays measuring TA in whole plants after A. thaliana cv 'Columbia' was challenged with fungal pathogen F. virguliforme. Infection caused significant variations in TAs. The total number of increased transcripts was nearly four times more than that of decreased transcripts in abundance. A putative resistance pathway involved in responding to the pathogen infection in A. thaliana was identified and compared to that reported in soybean. CONCLUSION: Microarray experiments allow the interrogation of tens of thousands of transcripts simultaneously and thus, the identification of plant pathways is likely to be involved in plant resistance to Fusarial pathogens. Dissection of the set functional orthologous genes between soybean and A. thaliana enabled a broad view of the functional relationships and molecular interactions among plant genes involved in F. virguliforme resistance.200818831797
32750.9991Natural variation in RPS2-mediated resistance among Arabidopsis accessions: correlation between gene expression profiles and phenotypic responses. Natural variation in gene expression (expression traits or e-traits) is increasingly used for the discovery of genes controlling traits. An important question is whether a particular e-trait is correlated with a phenotypic trait. Here, we examined the correlations between phenotypic traits and e-traits among 10 Arabidopsis thaliana accessions. We studied defense against Pseudomonas syringae pv tomato DC3000 (Pst), with a focus on resistance gene-mediated resistance triggered by the type III effector protein AvrRpt2. As phenotypic traits, we measured growth of the bacteria and extent of the hypersensitive response (HR) as measured by electrolyte leakage. Genetic variation among accessions affected growth of Pst both with (Pst avrRpt2) and without (Pst) the AvrRpt2 effector. Variation in HR was not correlated with variation in bacterial growth. We also collected gene expression profiles 6 h after mock and Pst avrRpt2 inoculation using a custom microarray. Clusters of genes whose expression levels are correlated with bacterial growth or electrolyte leakage were identified. Thus, we demonstrated that variation in gene expression profiles of Arabidopsis accessions collected at one time point under one experimental condition has the power to explain variation in phenotypic responses to pathogen attack.200718083910
32460.9991Capillary electrophoresis-based profiling and quantitation of total salicylic acid and related phenolics for analysis of early signaling in Arabidopsis disease resistance. A capillary electrophoresis-based method for quantitation of total salicylic acid levels in Arabidopsis leaves was developed. Direct comparison to previous high-performance liquid chromatography (HPLC)-based measurements showed similar levels of salicylic acid. Simultaneous quantitation of trans-cinnamic acid, benzoic acid, sinapic acid, and an internal recovery standard was achieved. A rapid, streamlined protocol with requirements for plant tissue reduced relative to those of HPLC-based protocols is presented. Complicated, multiparameter experiments were thus possible despite the labor-intensive nature of inoculating plants with bacterial pathogens. As an example of this sort of experiment, detailed time course studies of total salicylic acid accumulation by wild-type Arabidopsis and two lines with mutations affecting salicylic acid accumulation in response to either of two avirulent bacterial strains were performed. Accumulation in the first 12h was biphasic. The first phase was partially SID2 and NDR1 dependent with both bacterial strains. The second phase was largely independent of both genes with bacteria carrying avrB, but dependent upon both genes with bacteria carrying avrRpt2. Virulent bacteria did not elicit salicylic acid accumulation at these time points. Application of this method to various Arabidopsis pathosystems and the wealth of available disease resistance signaling mutants will refine knowledge of disease resistance and associated signal transduction.200312927828
25370.9991The Rxo1/ Rba1 locus of maize controls resistance reactions to pathogenic and non-host bacteria. Infiltration of different maize lines with a variety of bacterial pathogens of maize, rice and sorghum identified qualitative differences in resistant reactions. Isolates from two bacterial species induced rapid hypersensitive reactions (HR) in some maize lines, but not others. All isolates of the non-host pathogen Xanthomonas oryzae pv. oryzicola (bacterial leaf streak disease of rice) and some isolates of the pathogenic bacterium Burkholderia andropogonis induced HR when infiltrated into maize line B73, but not Mo17. Genetic control of the HR to both bacteria segregated as a single dominant gene. Surprisingly, both phenotypes mapped to the same locus, indicating they are either tightly linked or controlled by the same gene. The locus maps on the short arm of maize chromosome six near several other disease-resistance genes. Results indicate the same type of genes may contribute to both non-host resistance and resistance to pathogens.200415114472
841280.9991Transcriptomic profiling analysis of tilapia (Oreochromis niloticus) following Streptococcus agalactiae challenge. Innate immune system is the primary defense mechanism against pathogen infection in teleost, which are living in pathogen-rich aquatic environment. It has been long hypothesized that the disease resistance in teleost are strongly correlated to the activities of innate immune genes. Tilapia is an important economical fish around the world, especially in China, where the production accounts for nearly half of the global production. Recently, S. agalactiae has become one of the most serious bacterial diseases in southern China, resulted in high cumulative mortality and economic loss to tilapia industry. Therefore, we sought here to characterize the expression profiles of tilapia against S. agalactiae infection at whole transcriptome level by RNA-seq technology. A total of 2822 genes were revealed significantly expressed in tilapia spleen with a general trend of induction. Notably, most of the genes were rapidly the most induced at the early timepoint. The significantly changed genes highlighted the function of pathogen attachment and recognition, antioxidant/apoptosis, cytoskeletal rearrangement, and immune activation. Collectively, the induced expression patterns suggested the strong ability of tilapia to rapidly recognize the invasive bacteria, and activation of downstream immune signaling pathways to clear the bacteria and prevent the tissue damage and bacteria triggered cell apoptosis. Our results heighted important roles of novel candidate genes which were often missed in previous tilapia studies. Further studies are needed to characterize the molecular relationships between key immune genes and disease resistance, and to identify the candidate genes for molecular-assistant selection of disease-resistant broodstock and evaluation of disease prevention and treatment measures.201728111359
621690.9991Phosphoinositide 3-kinase family in channel catfish and their regulated expression after bacterial infection. The phosphoinositide-3-kinase (PI3Ks) family of lipid kinases is widely conserved from yeast to mammals. In this work, we identified a total of 14 members of the PI3Ks from the channel catfish genome and transcriptome and conducted phylogenetic and syntenic analyses of these genes. The expression profiles after infection with Edwardsiella ictaluri and Flavobacterium columnare were examined to determine the involvement of PI3Ks in immune responses after bacterial infection in catfish. The results indicated that PI3Ks genes including all of the catalytic subunit and several regulatory subunits genes were widely regulated after bacterial infection. The expression patterns were quite different when challenged with different bacteria. The PI3Ks were up-regulated rapidly at the early stage after ESC infection, but their induced expression was much slower, at the middle stage after columnaris infection. RNA-Seq datasets indicated that PI3K genes may be expressed at different levels in different catfish differing in their resistance levels against columnaris. Future studies are required to confirm and validate these observations. Taken together, this study indicated that PI3K genes may be involved as a part of the defense responses of catfish after infections, and they could be one of the determinants for disease resistance.201626772478
325100.9991Use of Arabidopsis thaliana and Pseudomonas syringae in the Study of Plant Disease Resistance and Tolerance. The interaction between Arabidopsis thaliana and the bacterium Pseudomonas syringae is being developed as a model experimental system for plant pathology research. Race-specific ("gene-for-gene") resistance has been demonstrated for this interaction, and pathogen genes that determine avirulence have been isolated and characterized. Because certain lines of both Arabidopsis and soybean are resistant to bacteria carrying the avirulence genes avrRpt2 and avrB, extremely similar pathogen recognition mechanisms are apparently present in these two plant species. Isogenic bacterial strains that differ by the presence of single avirulence genes are being used to analyze plant resistance. Plant resistance genes have been identified in crosses between resistant and susceptible lines. The extensive map-based cloning tools available in Arabidopsis are being used to isolate these resistance genes. In a related project, ethylene-insensitive Arabidopsis mutants are being used to examine the role of ethylene in disease development. Ethylene apparently mediates symptom formation in susceptible plants and is not required for resistance, suggesting possible strategies for enhancement of disease tolerance in crops.199319279805
96110.9991Genome-wide Identification, Classification, and Expression Analysis of the Receptor-Like Protein Family in Tomato. Receptor-like proteins (RLPs) are involved in plant development and disease resistance. Only some of the RLPs in tomato (Solanum lycopersicum L.) have been functionally characterized though 176 genes encoding RLPs, which have been identified in the tomato genome. To further understand the role of RLPs in tomato, we performed genome-guided classification and transcriptome analysis of these genes. Phylogenic comparisons revealed that the tomato RLP members could be divided into eight subgroups and that the genes evolved independently compared to similar genes in Arabidopsis. Based on location and physical clustering analyses, we conclude that tomato RLPs likely expanded primarily through tandem duplication events. According to tissue specific RNA-seq data, 71 RLPs were expressed in at least one of the following tissues: root, leaf, bud, flower, or fruit. Several genes had expression patterns that were tissue specific. In addition, tomato RLP expression profiles after infection with different pathogens showed distinguish gene regulations according to disease induction and resistance response as well as infection by bacteria and virus. Notably, Some RLPs were highly and/or unique expressed in susceptible tomato to pathogen, suggesting that the RLP could be involved in disease response, possibly as a host-susceptibility factor. Our study could provide an important clues for further investigations into the function of tomato RLPs involved in developmental and response to pathogens.201830369853
8454120.9991Identification of genes differentially expressed during interaction of resistant and susceptible apple cultivars (Malus x domestica) with Erwinia amylovora. BACKGROUND: The necrogenic enterobacterium, Erwinia amylovora is the causal agent of the fire blight (FB) disease in many Rosaceae species, including apple and pear. During the infection process, the bacteria induce an oxidative stress response with kinetics similar to those induced in an incompatible bacteria-plant interaction. No resistance mechanism to E. amylovora in host plants has yet been characterized, recent work has identified some molecular events which occur in resistant and/or susceptible host interaction with E. amylovora: In order to understand the mechanisms that characterize responses to FB, differentially expressed genes were identified by cDNA-AFLP analysis in resistant and susceptible apple genotypes after inoculation with E. amylovora. RESULTS: cDNA were isolated from M.26 (susceptible) and G.41 (resistant) apple tissues collected 2 h and 48 h after challenge with a virulent E. amylovora strain or mock (buffer) inoculated. To identify differentially expressed transcripts, electrophoretic banding patterns were obtained from cDNAs. In the AFLP experiments, M.26 and G.41 showed different patterns of expression, including genes specifically induced, not induced, or repressed by E. amylovora. In total, 190 ESTs differentially expressed between M.26 and G.41 were identified using 42 pairs of AFLP primers. cDNA-AFLP analysis of global EST expression in a resistant and a susceptible apple genotype identified different major classes of genes. EST sequencing data showed that genes linked to resistance, encoding proteins involved in recognition, signaling, defense and apoptosis, were modulated by E. amylovora in its host plant. The expression time course of some of these ESTs selected via a bioinformatic analysis has been characterized. CONCLUSION: These data are being used to develop hypotheses of resistance or susceptibility mechanisms in Malus to E. amylovora and provide an initial categorization of genes possibly involved in recognition events, early signaling responses the subsequent development of resistance or susceptibility. These data also provided potential candidates for improving apple resistance to fire blight either by marker-assisted selection or genetic engineering.201020047654
8406130.9990Available cloned genes and markers for genetic improvement of biotic stress resistance in rice. Biotic stress is one of the major threats to stable rice production. Climate change affects the shifting of pest outbreaks in time and space. Genetic improvement of biotic stress resistance in rice is a cost-effective and environment-friendly way to control diseases and pests compared to other methods such as chemical spraying. Fast deployment of the available and suitable genes/alleles in local elite varieties through marker-assisted selection (MAS) is crucial for stable high-yield rice production. In this review, we focused on consolidating all the available cloned genes/alleles conferring resistance against rice pathogens (virus, bacteria, and fungus) and insect pests, the corresponding donor materials, and the DNA markers linked to the identified genes. To date, 48 genes (independent loci) have been cloned for only major biotic stresses: seven genes for brown planthopper (BPH), 23 for blast, 13 for bacterial blight, and five for viruses. Physical locations of the 48 genes were graphically mapped on the 12 rice chromosomes so that breeders can easily find the locations of the target genes and distances among all the biotic stress resistance genes and any other target trait genes. For efficient use of the cloned genes, we collected all the publically available DNA markers (~500 markers) linked to the identified genes. In case of no available cloned genes yet for the other biotic stresses, we provided brief information such as donor germplasm, quantitative trait loci (QTLs), and the related papers. All the information described in this review can contribute to the fast genetic improvement of biotic stress resistance in rice for stable high-yield rice production.202337731986
84140.9990Two pathways act in an additive rather than obligatorily synergistic fashion to induce systemic acquired resistance and PR gene expression. BACKGROUND: Local infection with necrotizing pathogens induces whole plant immunity to secondary challenge. Pathogenesis-related genes are induced in parallel with this systemic acquired resistance response and thought to be co-regulated. The hypothesis of co-regulation has been challenged by induction of Arabidopsis PR-1 but not systemic acquired resistance in npr1 mutant plants responding to Pseudomonas syringae carrying the avirulence gene avrRpt2. However, experiments with ndr1 mutant plants have revealed major differences between avirulence genes. The ndr1-1 mutation prevents hypersensitive cell death, systemic acquired resistance and PR-1 induction elicited by bacteria carrying avrRpt2. This mutation does not prevent these responses to bacteria carrying avrB. RESULTS: Systemic acquired resistance, PR-1 induction and PR-5 induction were assessed in comparisons of npr1-2 and ndr1-1 mutant plants, double mutant plants, and wild-type plants. Systemic acquired resistance was displayed by all four plant lines in response to Pseudomonas syringae bacteria carrying avrB. PR-1 induction was partially impaired by either single mutation in response to either bacterial strain, but only fully impaired in the double mutant in response to avrRpt2. PR-5 induction was not fully impaired in any of the mutants in response to either avirulence gene. CONCLUSION: Two pathways act additively, rather than in an obligatorily synergistic fashion, to induce systemic acquired resistance, PR-1 and PR-5. One of these pathways is NPR1-independent and depends on signals associated with hypersensitive cell death. The other pathway is dependent on salicylic acid accumulation and acts through NPR1. At least two other pathways also contribute additively to PR-5 induction.200212381270
8794150.9990The Enhancement of Potato (Solanum Tuberosum L. Cv. Odyssey) Resistance to Bacterial Soft Rot Disease Through Transformation of the Glyphosate-Resistant Gene from Dickeya Dadanti. OBJECTIVE: An efficient protocol was developed via the Agrobacterium-mediated transformation method with the plasmid, p485, harboring the aroA gene from the bacterial species Dickeya dadantii, to improve resistance to potato bacterial soft rot disease. The study aimed to investigate the relationship between glyphosate application and the enhancement of potatoes' resistance to two bacterial pathogens affecting the plants. MATERIALS AND METHODS: An optimal concentration of 1.8 mg.L(-1) of glyphosate was applied to transgenic potato varieties. The leaves of the Odyssey cultivar demonstrated resistance to two pathogenic strains, Pectobacterium atrosepticum 21A and D. dadantii ENA49. Polymerase chain reaction (PCR) and reverse transcription-PCR (RT-PCR) validation demonstrated the successful integration and heterologous expression of the aroA gene in the potato genome. Additionally, the transcriptional analysis revealed the expression of pathogenesis-related genes and genes associated with the potato defence response. RESULTS: The study revealed a significant increase in the expression of pathogenesis-related genes (PR-2, PR-3, and PR-5) and defence response genes (HSR-203j and HIN1 in transgenic potato leaves after glyphosate treatment and subsequent exposure to pathogenic bacterial infection, with a particular emphasis on the upregulation of HSR-203j. A comparative analysis assessed the average expression levels of these genes in both experimental and control samples. In contrast, minimal changes in gene expression were observed in plants infected with bacteria but not treated with glyphosate. CONCLUSION: The study suggests that glyphosate treatment in potatoes can enhance systemic acquired resistance to bacterial pathogens by upregulating pathogenesis-related and defence response genes. This approach shows potential for addressing bacterial diseases in potatoes, including soft bacterial rot.202440225297
8882160.9990Transcriptome Profiling of Wild-Type and pga-Knockout Mutant Strains Reveal the Role of Exopolysaccharide in Aggregatibacter actinomycetemcomitans. Exopolysaccharides have a diverse set of functions in most bacteria including a mechanistic role in protecting bacteria against environmental stresses. Among the many functions attributed to the exopolysaccharides, biofilm formation, antibiotic resistance, immune evasion and colonization have been studied most extensively. The exopolysaccharide produced by many Gram positive as well as Gram negative bacteria including the oral pathogen Aggregatibacter actinomycetemcomitans is the homopolymer of β(1,6)-linked N-acetylglucosamine. Recently, we reported that the PGA-deficient mutant of A. actinomycetemcomitans failed to colonize or induce bone resorption in a rat model of periodontal disease, and the colonization genes, apiA and aae, were significantly down regulated in the mutant strain. To understand the role of exopolysaccharide and the pga locus in the global expression of A. actinomycetemcomitans, we have used comparative transcriptome profiling to identify differentially expressed genes in the wild-type strain in relation to the PGA-deficient strain. Transcriptome analysis revealed that about 50% of the genes are differently expressed (P < 0.05 and fold change >1.5). Our study demonstrated that the absence of the pga locus affects the genes involved in peptidoglycan recycling, glycogen storage, and virulence. Further, using confocal microscopy and plating assays, we show that the viability of pga mutant strain is significantly reduced during biofilm growth. Thus, this study highlights the importance of pga genes and the exopolysaccharide in the virulence of A. actinomycetemcomitans.201526221956
30170.9990RNA-Seq analysis of Citrus reticulata in the early stages of Xylella fastidiosa infection reveals auxin-related genes as a defense response. BACKGROUND: Citrus variegated chlorosis (CVC), caused by Xylella fastidiosa, is one the most important citrus diseases, and affects all varieties of sweet orange (Citrus sinensis L. Osb). On the other hand, among the Citrus genus there are different sources of resistance against X. fastidiosa. For these species identifying these defense genes could be an important step towards obtaining sweet orange resistant varieties through breeding or genetic engineering. To assess these genes we made use of mandarin (C. reticulata Blanco) that is known to be resistant to CVC and shares agronomical characteristics with sweet orange. Thus, we investigated the gene expression in Ponkan mandarin at one day after infection with X. fastidiosa, using RNA-seq. A set of genes considered key elements in the resistance was used to confirm its regulation in mandarin compared with the susceptible sweet orange. RESULTS: Gene expression analysis of mock inoculated and infected tissues of Ponkan mandarin identified 667 transcripts repressed and 724 significantly induced in the later. Among the induced transcripts, we identified genes encoding proteins similar to Pattern Recognition Receptors. Furthermore, many genes involved in secondary metabolism, biosynthesis and cell wall modification were upregulated as well as in synthesis of abscisic acid, jasmonic acid and auxin. CONCLUSIONS: This work demonstrated that the defense response to the perception of bacteria involves cell wall modification and activation of hormone pathways, which probably lead to the induction of other defense-related genes. We also hypothesized the induction of auxin-related genes indicates that resistant plants initially recognize X. fastidiosa as a necrotrophic pathogen.201324090429
8871180.9990Phage selection drives resistance-virulence trade-offs in Ralstonia solanacearum plant-pathogenic bacterium irrespective of the growth temperature. While temperature has been shown to affect the survival and growth of bacteria and their phage parasites, it is unclear if trade-offs between phage resistance and other bacterial traits depend on the temperature. Here, we experimentally compared the evolution of phage resistance-virulence trade-offs and underlying molecular mechanisms in phytopathogenic Ralstonia solanacearum bacterium at 25 °C and 35 °C temperature environments. We found that while phages reduced R. solanacearum densities relatively more at 25 °C, no difference in the final level of phage resistance was observed between temperature treatments. Instead, small colony variants (SCVs) with increased growth rate and mutations in the quorum-sensing (QS) signaling receptor gene, phcS, evolved in both temperature treatments. Interestingly, SCVs were also phage-resistant and reached higher frequencies in the presence of phages. Evolving phage resistance was costly, resulting in reduced carrying capacity, biofilm formation, and virulence in planta, possibly due to loss of QS-mediated expression of key virulence genes. We also observed mucoid phage-resistant colonies that showed loss of virulence and reduced twitching motility likely due to parallel mutations in prepilin peptidase gene, pilD. Moreover, phage-resistant SCVs from 35 °C-phage treatment had parallel mutations in type II secretion system (T2SS) genes (gspE and gspF). Adsorption assays confirmed the role of pilD as a phage receptor, while no loss of adsorption was found with phcS or T2SS mutants, indicative of other downstream phage resistance mechanisms. Additional transcriptomic analysis revealed upregulation of CBASS and type I restriction-modification phage defense systems in response to phage exposure, which coincided with reduced expression of motility and virulence-associated genes, including pilD and type II and III secretion systems. Together, these results suggest that while phage resistance-virulence trade-offs are not affected by the growth temperature, they could be mediated through both pre- and postinfection phage resistance mechanisms.202438525025
8795190.9990Transcriptome Analysis Reveals the Inducing Effect of Bacillus siamensis on Disease Resistance in Postharvest Mango Fruit. Postharvest anthracnose, caused by the fungus Colletotrichum gloeosporioides, is one of the most important postharvest diseases of mangoes worldwide. Bacillus siamensis (B. siamensis), as a biocontrol bacteria, has significant effects on inhibiting disease and improving the quality of fruits and vegetables. In this study, pre-storage application of B. siamensis significantly induced disease resistance and decreased disease index (DI) of stored mango fruit. To investigate the induction mechanisms of B. siamensis, comparative transcriptome analysis of mango fruit samples during the storage were established. In total, 234,808 unique transcripts were assembled and 56,704 differentially expressed genes (DEGs) were identified by comparative transcriptome analysis. Gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of DEGs showed that most of the DEGs involved in plant-pathogen interaction, plant hormone signal transduction, and biosynthesis of resistant substances were enriched. Fourteen DEGs related to disease-resistance were validated by qRT-PCR, which well corresponded to the FPKM value obtained from the transcriptome data. These results indicate that B. siamensis treatment may act to induce disease resistance of mango fruit by affecting multiple pathways. These findings not only reveal the transcriptional regulatory mechanisms that govern postharvest disease, but also develop a biological strategy to maintain quality of post-harvest mango fruit.202235010233