RESUMO
Abstract Bacterial leaf blight (BLB) is one of the major rice diseases in Malaysia. This disease causes substantial yield loss as high as 70%. Development of rice varieties which inherited BLB resistant traits is a crucial approach to promote and sustain rice industry in Malaysia. Hence, this study aims were to enhance BLB disease resistant characters of high yielding commercial variety MR219 through backcross breeding approach with supporting tool of marker-assisted selection (MAS). Broad spectrum BLB resistance gene, Xa7 from donor parent IRBB7 were introgressed into the susceptible MR219 (recurrent parent) using two flanking markers ID7 and ID15. At BC3F4, we managed to generate 19 introgressed lines with homozygous Xa7 gene and showed resistant characteristics as donor parent when it was challenged with Xanthomonas oryzae pv. oryzae through artificial inoculation. Recurrent parent MR219 and control variety, MR263 were found to be severely infected by the disease. The improved lines exhibited similar morphological and yield performance characters as to the elite variety, MR219. Two lines, PB-2-107 and PB-2-34 were chosen to be potential lines because of their outstanding performances compared to parent, MR219. This study demonstrates a success story of MAS application in development of improved disease resistance lines of rice against BLB disease.
Resumo A mancha bacteriana das folhas (BLB) é uma das principais doenças do arroz na Malásia. Essa doença causa perdas substanciais de rendimento de até 70%. O desenvolvimento de variedades de arroz que herdaram características de resistência ao BLB é uma abordagem crucial para promover e sustentar a indústria do arroz na Malásia. Portanto, o objetivo deste estudo foi aumentar os caracteres BLB resistentes a doenças da variedade comercial MR219 de alto rendimento por meio de uma abordagem de cruzamento retrocruzamento com ferramenta de apoio de seleção assistida por marcador (MAS). O gene de resistência a BLB de amplo espectro, Xa7 do pai doador IRBB7, foi introgressado no MR219 suscetível (pai recorrente) usando dois marcadores flanqueadores ID7 e ID15. No BC3F4, conseguimos gerar 19 linhagens introgressadas com o gene Xa7 homozigoto e apresentamos características de resistência como genitor doador quando desafiado com Xanthomonas oryzae pv. oryzae por inoculação artificial. O pai recorrente MR219 e a variedade controle, MR263, estavam gravemente infectados pela doença. As linhas melhoradas exibiram características morfológicas e de desempenho de rendimento semelhantes às da variedade elite, MR219. Duas linhas, PB-2-107 e PB-2-34, foram escolhidas como linhas potenciais por causa de seus desempenhos excelentes em comparação com a mãe, MR219. Este estudo demonstra uma história de sucesso de aplicação de MAS no desenvolvimento de linhas de arroz melhoradas com resistência a doenças contra a doença BLB.
Assuntos
Oryza , Xanthomonas , Doenças das Plantas/genética , Resistência à Doença/genética , Melhoramento VegetalRESUMO
Banana Xanthomonas wilt (BXW) caused by Xanthomonas campestris pv. musacearum (Xcm) is a severe bacterial disease affecting banana production in East and Central Africa, where banana is cultivated as a staple crop. Classical breeding of banana is challenging because the crop is clonally propagated and has limited genetic diversity. Thus, genetic engineering serves as a viable alternative for banana improvement. Studies have shown that transfer of the elongation factor Tu receptor gene (AtEFR) from Arabidopsis thaliana to other plant species can enhance resistance against bacterial diseases. However, AtEFR activity in banana and its efficacy against Xcm has not been demonstrated. In this study, transgenic events of banana (Musa acuminata) cultivar dwarf Cavendish expressing the AtEFR gene were generated and evaluated for resistance against Xcm under greenhouse conditions. The transgenic banana events were responsive to the EF-Tu-derived elf18 peptide and exhibited enhanced resistance to BXW disease compared to non-transgenic control plants. This study suggests that the functionality of AtEFR is retained in banana with the potential of enhancing resistance to BXW under field conditions.
Assuntos
Arabidopsis , Musa , Xanthomonas campestris , Xanthomonas , Xanthomonas campestris/genética , Arabidopsis/genética , Musa/genética , Melhoramento VegetalRESUMO
Introduction: Many Gram-negative plant- and animal-pathogenic bacteria employ type IV secretion (T4S) systems to transport proteins or DNA/protein complexes into eukaryotic or bacterial target cells. T4S systems have been divided into minimized and expanded T4S systems and resemble the VirB/VirD4 T4S system from the plant pathogen Agrobacterium tumefaciens and the Icm/Dot T4S system from the human pathogen Legionella pneumophila, respectively. The only known plant pathogen with both types of T4S systems is Xanthomonas euvesicatoria which is the causal agent of bacterial spot disease on pepper and tomato plants. Results and discussion: In the present study, we show that virB/virD4 and icm/dot T4S genes are expressed and encode components of oligomeric complexes corresponding to known assemblies of VirB/VirD4 and Icm/Dot proteins. Both T4S systems are dispensable for the interaction of X. euvesicatoria with its host plants and do not seem to confer contact-dependent lysis of other bacteria, which was previously shown for the chromosomally encoded VirB/VirD4 T4S system from Xanthomonas axonopodis pv. citri. The corresponding chromosomal T4S gene cluster from X. euvesicatoria is incomplete, however, the second plasmid-localized vir gene cluster encodes a functional VirB/VirD4 T4S system which contributes to plasmid transfer. In agreement with this finding, we identified the predicted relaxase TraI as substrate of the T4S systems from X. euvesicatoria. TraI and additional candidate T4S substrates with homology to T4S effectors from X. axonopodis pv. citri interact with the T4S coupling protein VirD4. Interestingly, however, the predicted C-terminal VirD4-binding sites are not sufficient for T4S, suggesting the contribution of additional yet unknown mechanisms to the targeting of T4S substrates from X. euvesicatoria to both VirB/VirD4 and Icm/Dot T4S systems.
Assuntos
Legionella pneumophila , Xanthomonas , Animais , Humanos , Sistemas de Secreção Tipo IV/genética , Eucariotos , Xanthomonas/genéticaRESUMO
Pathogenic Xanthomonas bacteria cause disease on more than 400 plant species. These Gram-negative bacteria utilize the type III secretion system to inject type III effector proteins (T3Es) directly into the plant cell cytosol where they can manipulate plant pathways to promote virulence. The host range of a given Xanthomonas species is limited, and T3E repertoires are specialized during interactions with specific plant species. Some effectors, however, are retained across most strains, such as Xanthomonas Outer Protein L (XopL). As an 'ancestral' effector, XopL contributes to the virulence of multiple xanthomonads, infecting diverse plant species. XopL homologs harbor a combination of a leucine-rich-repeat (LRR) domain and an XL-box which has E3 ligase activity. Despite similar domain structure there is evidence to suggest that XopL function has diverged, exemplified by the finding that XopLs expressed in plants often display bacterial species-dependent differences in their sub-cellular localization and plant cell death reactions. We found that XopL from X. euvesicatoria (XopLXe) directly associates with plant microtubules (MTs) and causes strong cell death in agroinfection assays in N. benthamiana. Localization of XopLXe homologs from three additional Xanthomonas species, of diverse infection strategy and plant host, revealed that the distantly related X. campestris pv. campestris harbors a XopL (XopLXcc) that fails to localize to MTs and to cause plant cell death. Comparative sequence analyses of MT-binding XopLs and XopLXcc identified a proline-rich-region (PRR)/α-helical region important for MT localization. Functional analyses of XopLXe truncations and amino acid exchanges within the PRR suggest that MT-localized XopL activity is required for plant cell death reactions. This study exemplifies how the study of a T3E within the context of a genus rather than a single species can shed light on how effector localization is linked to biochemical activity.
Assuntos
Xanthomonas campestris , Xanthomonas , Xanthomonas/genética , Xanthomonas/metabolismo , Proteínas de Bactérias/metabolismo , Células Vegetais/metabolismo , Plantas/metabolismo , Morte Celular , Microtúbulos/metabolismo , Doenças das Plantas/microbiologia , Xanthomonas campestris/genética , Xanthomonas campestris/metabolismoRESUMO
The purpose of the current study was to explore root endophytes- Priestia megaterium T3 and Bacillus cereus T4 from Moringa olefiera for the suppression of leaf spot disease in tomato plants challenged with Xanthomonas vesicatoria. Both strains had plant growth-stimulating characteristics including auxin production, solubilization of inorganic phosphate and zinc complexes, and production of ammonia, siderophore, as well as hydrolytic enzymes. An agar well diffusion and fluorescence viability assay have validated the antibacterial effect of the cell-free culture supernatant of strains T3 and T4. Liquid chromatography-mass spectrometry (LC-MS) profiling has identified the secondary metabolites in the cell-free supernatant of strains T3 and T4. The bio-priming of tomato seeds with a consortium of T3 and T4 strains has significantly declined ethylene (by 0.61-fold) and hydrogen peroxide (H2O2, 0.64-fold) concentration thus, maintaining a lower content of ROS-induced malondialdehyde (MDA, 0.91-fold) as compared to control counterparts. Consequently, the leaf spot disease severity was reduced by â¼70% in consortium-treated tomato plants in contrast to their pathogen-challenged control. The consortia (T3+T4) treatment has facilitated induced systemic resistance by enhancing enzymatic activities of phenylalanine ammonia-lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO), catalase (CAT), and ascorbate oxidase (AO) to detoxify the excessive Xanthomonas-induced ROS accumulation in tomato plants. Conclusively, bacterial endophytes modulate X. vesicatoria-induced ROS response and ethylene levels in tomato plants. The current findings indicate that plant growth-promoting endophytic bacterial strains hold the potential to sustainably enhance plant growth and suppress bacterial leaf spot disease in tomato plants.
Assuntos
Bacillales , Bacillus cereus , Doenças das Plantas , Solanum lycopersicum , Xanthomonas , Moringa oleifera/microbiologia , Raízes de Plantas/microbiologia , Espécies Reativas de Oxigênio/metabolismoRESUMO
Citrus canker, caused by the bacterium Xanthomonas citri (Xcc), is one of the most devastating diseases for the citrus industry. Xylose is a constituent of the cell wall of plants, and the ability of Xcc to use this carbohydrate may play a role in virulence. Xcc has two genes codifying for xylose isomerase (XI), a bifunctional enzyme that interconverts D-xylose into D-xylulose and D-glucose into D-fructose. The aim of this work was to investigate the functional role of the two putative XI ORFs, XAC1776 (xylA1) and XAC4225 (xylA2), in Xcc pathogenicity. XI-coding genes of Xcc were deleted, and the single mutants (XccΔxylA1 or XccΔxylA2) or the double mutant (XccΔxylA1ΔxylA2) remained viable. The deletion of one or both XI genes (xylA1 and/or xylA2) increased the aggressiveness of the mutants, causing disease symptoms. RT-qPCR analysis of wild strain and xylA deletion mutants grown in vivo and in vitro revealed that the highest expression level of hrpX and xylR was observed in vivo for the double mutant. The results indicate that XI depletion increases the expression of the hrp regulatory genes in Xcc. We concluded that the intracellular accumulation of xylose enhances Xcc virulence.
Assuntos
Citrus , Xanthomonas , Virulência/genética , Xilose/metabolismo , Citrus/metabolismo , Doenças das Plantas/microbiologiaRESUMO
Nowadays, reactive oxygen species (ROS) have been acknowledged as promising bactericidal targets against pesticide-resistant bacteria. Herein, to further excavate more excellent ROS inducers, simple 1,2,3,4-tetrahydro-ß-carboline derivatives containing a 3-aminopropanamide moiety were prepared and assessed for their antibacterial potency. Notably, three promising compounds displayed significant antibacterial potency. Compound I29 exhibits excellent in vitro bioactivity, with an EC50 value of 5.73 µg/mL, and admirable in vivo activities (protective activity of 55.74% and curative activity of 65.50%) toward Xanthomonas oryzae pv. oryzae. Compound I16 has good activity in vitro, with an EC50 of 3.43 µg/mL, and outstanding bioactivities in vivo (protective activity of 92.50% and curative activity of 59.68%) against Xanthomonas axonopodis pv. citri. Compound I6 shows excellent in vitro bioactivity (EC50 = 2.86 µg/mL) and significant protective activity (94.02%) for preventing Pseudomonas syringae pv. actinidiae. Antibacterial mechanism investigations indicate that these compounds disrupt the balance of the redox system to kill bacteria. These simple 1,2,3,4-tetrahydro-ß-carboline derivatives are promising leads to the discovery of bactericidal agents.
Assuntos
Infecções Bacterianas , Oryza , Xanthomonas , Espécies Reativas de Oxigênio , Testes de Sensibilidade Microbiana , Doenças das Plantas/microbiologia , Antibacterianos/farmacologia , Antibacterianos/química , Oryza/microbiologia , Oxidiazóis/químicaRESUMO
Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of bacterial blight, one of the most devastating diseases of rice. Pathogenic bacteria possess numerous transcriptional regulators to participate in the regulation of cellular processes. Here, we identified a transcriptional regulator Gar (PXO_RS11965) that is involved in regulating the growth and virulence of Xoo. Notably, the knockout of gar in Xoo enhanced bacterial virulence to the host rice. RNA-sequencing analysis and quantitative ß-glucuronidase (GUS) assay indicated that Gar positively regulates the expression of a σ54 factor rpoN2. Further experiments confirmed that overexpression of rpoN2 restored the phenotypic changes caused by gar deletion. Our research revealed that Gar influences bacterial growth and virulence by positively regulating the expression of rpoN2.
Assuntos
Oryza , Xanthomonas , Virulência/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica , Doenças das Plantas/microbiologia , Xanthomonas/metabolismo , Oryza/microbiologiaRESUMO
Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is a destructive citrus disease worldwide. Generating disease-resistant cultivars is the most effective, environmentally friendly and economic approach for disease control. However, citrus traditional breeding is lengthy and laborious. Here, we develop transgene-free canker-resistant Citrus sinensis lines in the T0 generation within 10 months through transformation of embryogenic protoplasts with Cas12a/crRNA ribonucleoprotein to edit the canker susceptibility gene CsLOB1. Among the 39 regenerated lines, 38 are biallelic/homozygous mutants, demonstrating a 97.4% biallelic/homozygous mutation rate. No off-target mutations are detected in the edited lines. Canker resistance of the cslob1-edited lines results from both abolishing canker symptoms and inhibiting Xcc growth. The transgene-free canker-resistant C. sinensis lines have received regulatory approval by USDA APHIS and are exempted from EPA regulation. This study provides a sustainable and efficient citrus canker control solution and presents an efficient transgene-free genome-editing strategy for citrus and other crops.
Assuntos
Citrus sinensis , Citrus , Xanthomonas , Citrus sinensis/genética , RNA Guia de Sistemas CRISPR-Cas , Sistemas CRISPR-Cas/genética , Resistência à Doença/genética , Melhoramento Vegetal , Citrus/genética , Xanthomonas/genética , Doenças das Plantas/genéticaRESUMO
In this paper, a series of derivatives were synthesized by introducing the pharmacophore pyrazole ring and piperazine ring into the structure of the natural product myricetin through an amide bond. The structures were determined using carbon spectrum and hydrogen spectrum high-resolution mass spectrometry. Biological activities of those compounds against bacteria, including Xac (Xanthomonas axonopodis pv. Citri), Psa (Pseudomonas syringae pv. Actinidiae) and Xoo (Xanthomonas oryzae pv. Oryzae) were tested. Notably, D6 exhibited significant bioactivity against Xoo with an EC50 value of 18.8 µg/mL, which was higher than the control drugs thiadiazole-copper (EC50 = 52.9 µg/mL) and bismerthiazol (EC50 = 69.1 µg/mL). Furthermore, the target compounds were assessed for their antifungal activity against ten plant pathogenic fungi. Among them, D1 displayed excellent inhibitory activity against Phomopsis sp. with an EC50 value of 16.9 µg/mL, outperforming the control agents azoxystrobin (EC50 = 50.7 µg/mL) and fluopyram (EC50 = 71.8 µg/mL). In vitro tests demonstrated that D1 possessed curative (60.6%) and protective (74.9%) effects on postharvest kiwifruit. To investigate the active mechanism of D1, its impact on SDH activity was evaluated based on its structural features and further confirmed through molecular docking. Subsequently, the malondialdehyde content of D1-treated fungi was measured, revealing that D1 could increase malondialdehyde levels, thereby causing damage to the cell membrane. Additionally, the EC50 value of D16 on P. capsici was 11.3 µg/mL, which was superior to the control drug azoxystrobin (EC50 = 35.1 µg/mL), and the scanning electron microscopy results indicated that the surface of drug-treated mycelium was ruffled, and growth was significantly affected.
Assuntos
Oryza , Xanthomonas , Amidas/farmacologia , Piperazina , Simulação de Acoplamento Molecular , Antibacterianos/farmacologia , Testes de Sensibilidade Microbiana , Doenças das Plantas/microbiologia , Oryza/microbiologia , Relação Estrutura-AtividadeRESUMO
Developing new agricultural bactericides is a feasible strategy for stopping the increase in the resistance of plant pathogenic bacteria. Some pentacyclic triterpene acid derivatives were elaborately designed and synthesized. In particular, compound A22 exhibited the best antimicrobial activity against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac) with EC50 values of 3.34 and 3.30 mg L-1, respectively. The antimicrobial mechanism showed that the compound A22 induced excessive production and accumulation of reactive oxygen species (ROS) in Xoo cells, leading to a decrease in superoxide dismutase and catalase enzyme activities and an increase in malondialdehyde content. A22 also produced increases in Xoo cell membrane permeability and eventual cell death. In addition, in vivo experiments showed that A22 at 200 mg L-1 exhibited protective activity against rice bacterial blight (50.44%) and citrus canker disease (84.37%). Therefore, this study provides a paradigm for the agricultural application of pentacyclic triterpene acid.
Assuntos
Oryza , Triterpenos , Xanthomonas , Espécies Reativas de Oxigênio/metabolismo , Amidas/metabolismo , Triterpenos/farmacologia , Triterpenos/metabolismo , Xanthomonas/metabolismo , Antibacterianos/farmacologia , Antibacterianos/metabolismo , Oryza/metabolismo , Triterpenos Pentacíclicos/farmacologia , Triterpenos Pentacíclicos/metabolismo , Doenças das Plantas/microbiologia , Testes de Sensibilidade MicrobianaRESUMO
Rice bacterial leaf blight is a destructive bacterial disease caused by Xanthomonas oryzae pv. oryzae (Xoo) that seriously threatens crop yields and their associated economic benefits. In this study, a series of improved dissolubility 7-aliphatic amine tryptanthrin derivatives was designed and synthesized, and their potency in antibacterial applications was investigated. Notably, compound 6e exhibited excellent activity against Xoo, with an EC50 value of 2.55 µg/mL, compared with the positive control bismerthiazol (EC50 = 35.0 µg/mL) and thiodiazole copper (EC50 = 79.4 µg/mL). In vivo assays demonstrated that 6e exhibited a significant protective effect on rice leaves. After exposure, the morphology of the bacteria was partially atrophied by SEM. Furthermore, 6e increased the accumulation of intracellular reactive oxygen species, causing cell apoptosis and the formation of bacterial biofilms. All the results indicated that 6e could be a potential agrochemical bactericide for controlling phytopathogenic bacteria.
Assuntos
Oryza , Xanthomonas , Oxidiazóis/farmacologia , Testes de Sensibilidade Microbiana , Doenças das Plantas/prevenção & controle , Doenças das Plantas/microbiologia , Antibacterianos/farmacologia , Antibacterianos/química , Oryza/microbiologiaRESUMO
ß-Carbonic anhydrase (ßCA) is very important for plant growth and development, but its function in immunity has also been examined. In this study, we found that the expression level of Solanum lycopersicum ßCA1 (SlßCA1) was significantly upregulated in plants treated with Xanthomonas euvesicatoria 85-10. The protein was localized in the nucleus, cell membrane and chloroplast. Using tomato plants silenced with SlßCA1, we demonstrated that SlßCA1 plays an active role in plant disease resistance. Moreover, we found that the elicitor PopW upregulated the expression of SlßCA1, while the microbe-associated molecular pattern response induced by PopW was inhibited in TRV-SlßCA1. The interaction between PopW and SlßCA1 was confirmed. Here, we found that SlßCA1 was positively regulated during PopW-induced resistance to Xanthomonas euvesicatoria 85-10. These data indicate the importance of SlßCA1 in plant basic immunity and its recognition by the Harpin protein PopW as a new target for elicitor recognition.
Assuntos
Solanum lycopersicum , Xanthomonas , Solanum lycopersicum/genética , Xanthomonas/fisiologia , Proteínas de Bactérias/metabolismo , Imunidade Vegetal/genética , Doenças das Plantas/genéticaRESUMO
Bacterial blight of pomegranate caused by Xanthomonas auxonopodis pv.punicae (Xap) threaten the existence of a group of farmers for the past few decades who rely on pomegranate cultivation for their livelihood since it will cause huge yield loss. The primary focus of this study was to conduct a thorough analysis of the characterization of this blight incitant Xap. Physiological, biochemical, and molecular characteristics of six phytopathogenic strains of Xap, designated as PBF1 (PBF: Pomegranate Blight Fruit), PBF2, PBF3, PBF4, PBF5, and PBF6, isolated from the infected fruits were examined. Bacterial colonies were featured as gram-negative, yellow-pigmented circular with a glistening appearance. An attempt to determine the best culture medium, favouring bacterial proliferation was successfully done with four distinct medium, Nutrient Glucose Agar (NGA), Nutrient sucrose Agar (NSA), Yeast Dextrose Calcium Carbonate Agar (YDCA) and Yeast Glucose Calcium Carbonate Agar (YGCA) and comparatively, significant growth was found in NGA (66.66%) followed by YDCA (33%). According to the antibiotic susceptibility results, both ampicillin and streptomycin were determined as potentially effective drugs in preventing the proliferation of Xap (P 0.05). The reactive oxygen species-mediated plant immune response during host-pathogen interaction was confirmed by accessing the presence of H2O2 accumulation in infected leaves via 3,3 - diaminobenzidine (DAB) -staining technique. Bacterial isolates from this study were confirmed by two universal constitutive genes such as gyrB and 16S rRNA. From the BLAST analysis, the isolates were identified as Xap with base pair lengths of 1408bp, 1180bp, and 1159bp, which correspond to PBF1, PBF2, and PBF3, respectively. A neighbor-joining phylogenetic tree study explaining a strong phylogenetic relationship between the query sequence and closely related bacterial species.
Assuntos
Punica granatum , Xanthomonas , Punica granatum/genética , Xanthomonas/genética , Frutas/microbiologia , Peróxido de Hidrogênio , Doenças das Plantas/microbiologia , Ágar , RNA Ribossômico 16S/genética , Saccharomyces cerevisiae/genética , Filogenia , Interações Hospedeiro-Patógeno , GlucoseRESUMO
Xanthomonas campestris is an important member of the Xanthomonas group of phytopathogens that causes diseases in crucifers. In X. campestris, several virulence-associated functions, including some belonging to unknown predicted functions, have been implicated in the colonization and disease processes. However, the role of many of these unknown predicted proteins in Xanthomonas-host interaction and their exact physiological function is not clearly known. In this study, we identified a novel membrane-associated protein belonging to the DedA super family, XdfA, which is required for virulence in X. campestris. The DedA family of proteins are generally ubiquitous in bacteria; however, their function and actual physiological role are largely elusive. Characterization of ∆xdfA by homology modeling, membrane localization, and physiological studies indicated that XdfA is a membrane-associated protein that plays a role in the maintenance of membrane integrity. Furthermore, functional homology modeling analysis revealed that the XdfA exhibits structural similarity to a CorA-like magnesium transporter and is required for optimum growth under low magnesium ion concentration. We report for the first time that a putative DedA family of protein in Xanthomonas is required for optimum virulence and plays a role in the maintenance of membrane-associated functions and magnesium homeostasis. IMPORTANCE Bacterial DedA family proteins are involved in a range of cellular processes such as ion transport, signal transduction, and cell division. Here, we have discussed about a novel DedA family protein XdfA in Xanthomonas campestris pv. campestris that has a role in membrane homeostasis, magnesium transport, and virulence. Understanding membrane and magnesium homeostasis will aid in our comprehension of bacterial physiology and eventually will help us devise effective antimicrobial strategies to safeguard horticulturally and agriculturally important crop plants.
Assuntos
Xanthomonas campestris , Xanthomonas , Virulência , Xanthomonas campestris/genética , Magnésio , Proteínas de Membrana , Fatores de Virulência/genética , Fatores de Virulência/metabolismo , Xanthomonas/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Doenças das Plantas/microbiologiaRESUMO
Herbarium collections are an important source of dated, identified and preserved DNA, whose use in comparative genomics and phylogeography can shed light on the emergence and evolutionary history of plant pathogens. Here, we reconstruct 13 historical genomes of the bacterial crop pathogen Xanthomonas citri pv. citri (Xci) from infected Citrus herbarium specimens. Following authentication based on ancient DNA damage patterns, we compare them with a large set of modern genomes to estimate their phylogenetic relationships, pathogenicity-associated gene content and several evolutionary parameters. Our results indicate that Xci originated in Southern Asia ~11,500 years ago (perhaps in relation to Neolithic climate change and the development of agriculture) and diversified during the beginning of the 13th century, after Citrus diversification and before spreading to the rest of the world (probably via human-driven expansion of citriculture through early East-West trade and colonization).
Assuntos
Citrus , Xanthomonas , Humanos , Filogenia , Xanthomonas/genética , Genômica , Citrus/microbiologia , Doenças das Plantas/microbiologiaRESUMO
Citrus bacterial canker (CBC), caused by Xanthomonas citri subsp. citri (Xcc), causes dramatic losses to the citrus industry worldwide. Transcription activator-like effectors (TALEs), which bind to effector binding elements (EBEs) in host promoters and activate transcription of downstream host genes, contribute significantly to Xcc virulence. The discovery of the biochemical context for the binding of TALEs to matching EBE motifs, an interaction commonly referred to as the TALE code, enabled the in silico prediction of EBEs for each TALE protein. Using the TALE code, we engineered a synthetic resistance (R) gene, called the Xcc-TALE-trap, in which 14 tandemly arranged EBEs, each capable of autonomously recognizing a particular Xcc TALE, drive the expression of Xanthomonas avrGf2, which encodes a bacterial effector that induces plant cell death. Analysis of a corresponding transgenic Duncan grapefruit showed that transcription of the cell death-inducing executor gene, avrGf2, was strictly TALE-dependent and could be activated by several different Xcc TALE proteins. Evaluation of Xcc strains from different continents showed that the Xcc-TALE-trap mediates resistance to this global panel of Xcc isolates. We also studied in planta-evolved TALEs (eTALEs) with novel DNA-binding domains and found that these eTALEs also activate the Xcc-TALE-trap, suggesting that the Xcc-TALE-trap is likely to confer durable resistance to Xcc. Finally, we show that the Xcc-TALE-trap confers resistance not only in laboratory infection assays but also in more agriculturally relevant field studies. In conclusion, transgenic plants containing the Xcc-TALE-trap offer a promising sustainable approach to control CBC.
Assuntos
Citrus , Xanthomonas , Efetores Semelhantes a Ativadores de Transcrição/genética , Efetores Semelhantes a Ativadores de Transcrição/metabolismo , Citrus/genética , Citrus/microbiologia , Xanthomonas/genética , Regiões Promotoras Genéticas/genética , Doenças das Plantas/genética , Doenças das Plantas/microbiologiaRESUMO
Background: There has been limited exploration of copLAB genotypes and associated copper resistance phenotypes in Xanthomonas spp. in the southern Caribbean region. An earlier study highlighted a variant copLAB gene cluster found in one Trinidadian Xanthomonas campestris pv. campestris (Xcc) strain (BrA1), with <90% similarity to previously reported Xanthomonas copLAB genes. With only one report describing this copper resistance genotype, the current study investigated the distribution of the BrA1 variant copLAB gene cluster and previously reported forms of copper resistance genes in local Xanthomonas spp. Methods: Xanthomonas spp. were isolated from black-rot infected lesions on leaf tissue from crucifer crops at intensively farmed sites with high agrochemical usage in Trinidad. The identity of morphologically identified isolates were confirmed using a paired primer PCR based screen and 16s rRNA partial gene sequencing. MGY agar amended with CuSO4.5H2O up to 2.4 mM was used to establish MIC's for confirmed isolates and group strains as sensitive, tolerant, or resistant to copper. Separate primer pairs targeting the BrA1 variant copLAB genes and those predicted to target multiple homologs found in Xanthomonas and Stenotrophomonas spp. were used to screen copper resistant isolates. Select amplicons were sanger sequenced and evolutionary relationships inferred from global reference sequences using a ML approach. Results: Only four copper sensitive/tolerant Xanthomonas sp. strains were isolated, with 35 others classed as copper-resistant from a total population of 45 isolates. PCR detection of copLAB genes revealed two PCR negative copper-resistant resistant strains. Variant copLAB genes were only found in Xcc from the original source location of the BrA1 strain, Aranguez. Other copper-resistant strains contained other copLAB homologs that clustered into three distinct clades. These groups were more similar to genes from X. perforans plasmids and Stenotrophomonas spp. chromosomal homologs than reference Xcc sequences. This study highlights the localisation of the BrA1 variant copLAB genes to one agricultural community and the presence of three distinct copLAB gene groupings in Xcc and related Xanthomonas spp. with defined CuSO4.5H2O MIC. Further characterisation of these gene groups and copper resistance gene exchange dynamics on and within leaf tissue between Xcc and other Xanthomonas species are needed as similar gene clusters showed variable copper sensitivity profiles. This work will serve as a baseline for copper resistance gene characterisation in Trinidad and the wider Caribbean region and can be used to boost already lacking resistant phytopathogen management in the region.
Assuntos
Xanthomonas campestris , Xanthomonas , Xanthomonas/genética , Cobre/farmacologia , RNA Ribossômico 16S/genética , Prevalência , Xanthomonas campestris/genéticaRESUMO
Bacterial leaf blight (BB) of rice, caused by Xanthomonas oryzae pv. oryzae (Xoo), threatens global food security and the livelihood of small-scale rice producers. Analyses of Xoo collections from Asia, Africa and the Americas demonstrated complete continental segregation, despite robust global rice trade. Here, we report unprecedented BB outbreaks in Tanzania. The causative strains, unlike endemic African Xoo, carry Asian-type TAL effectors targeting the sucrose transporter SWEET11a and iTALes suppressing Xa1. Phylogenomics clustered these strains with Xoo from Southern-China. African rice varieties do not carry effective resistance. To protect African rice production against this emerging threat, we developed a hybrid CRISPR-Cas9/Cpf1 system to edit all known TALe-binding elements in three SWEET promoters of the East African elite variety Komboka. The edited lines show broad-spectrum resistance against Asian and African strains of Xoo, including strains recently discovered in Tanzania. The strategy could help to protect global rice crops from BB pandemics.
