Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 711
Filtrar
1.
Int J Mol Sci ; 22(19)2021 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-34638715

RESUMO

Walnut blight is a significant above-ground disease of walnuts caused by Xanthomonas arboricola pv. juglandis (Xaj). The secreted form of chorismate mutase (CM), a key enzyme of the shikimate pathway regulating plant immunity, is highly conserved between plant-associated beta and gamma proteobacteria including phytopathogens belonging to the Xanthomonadaceae family. To define its role in walnut blight disease, a dysfunctional mutant of chorismate mutase was created in a copper resistant strain Xaj417 (XajCM). Infections of immature walnut Juglans regia (Jr) fruit with XajCM were hypervirulent compared with infections with the wildtype Xaj417 strain. The in vitro growth rate, size and cellular morphology were similar between the wild-type and XajCM mutant strains, however the quantification of bacterial cells by dPCR within walnut hull tissues showed a 27% increase in XajCM seven days post-infection. To define the mechanism of hypervirulence, proteome analysis was conducted to compare walnut hull tissues inoculated with the wild type to those inoculated with the XajCM mutant strain. Proteome analysis revealed 3296 Jr proteins (five decreased and ten increased with FDR ≤ 0.05) and 676 Xaj417 proteins (235 increased in XajCM with FDR ≤ 0.05). Interestingly, the most abundant protein in Xaj was a polygalacturonase, while in Jr it was a polygalacturonase inhibitor. These results suggest that this secreted chorismate mutase may be an important virulence suppressor gene that regulates Xaj417 virulence response, allowing for improved bacterial survival in the plant tissues.


Assuntos
Proteínas de Bactérias/metabolismo , Corismato Mutase/metabolismo , Juglans/microbiologia , Doenças das Plantas/microbiologia , Xanthomonas , Xanthomonas/enzimologia , Xanthomonas/patogenicidade
2.
Int J Mol Sci ; 22(18)2021 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-34576034

RESUMO

Crown roots are essential for plants to obtain water and nutrients, perceive environmental changes, and synthesize plant hormones. In this study, we identified and characterized short crown root 8 (scr8), which exhibited a defective phenotype of crown root and vegetative development. Temperature treatment showed that scr8 was sensitive to temperature and that the mutant phenotypes were rescued when grown under low temperature condition (20 °C). Histological and EdU staining analysis showed that the crown root formation was hampered and that the root meristem activity was decreased in scr8. With map-based cloning strategy, the SCR8 gene was fine-mapped to an interval of 126.4 kb on chromosome 8. Sequencing analysis revealed that the sequence variations were only found in LOC_Os08g14850, which encodes a CC-NBS-LRR protein. Expression and inoculation test analysis showed that the expression level of LOC_Os08g14850 was significantly decreased under low temperature (20 °C) and that the resistance to Xanthomonas oryzae pv. Oryzae (Xoo) was enhanced in scr8. These results indicated that LOC_Os08g14850 may be the candidate of SCR8 and that its mutation activated the plant defense response, resulting in a crown root growth defect.


Assuntos
Organogênese Vegetal/genética , Oryza/genética , Doenças das Plantas/genética , Proteínas de Plantas/genética , Resistência à Doença/genética , Regulação da Expressão Gênica de Plantas/genética , Mutação/genética , Oryza/crescimento & desenvolvimento , Oryza/microbiologia , Fenótipo , Doenças das Plantas/microbiologia , Plantas Geneticamente Modificadas/genética , Temperatura , Xanthomonas/genética , Xanthomonas/patogenicidade
3.
Arch Microbiol ; 203(9): 5453-5462, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34406444

RESUMO

The selective infection of Xanthomonas citri pv. citri (Xcc) to citrus cultivars is universally known, but the relationship between endophytic bacteria and the resistance of host variety to canker disease remains unclear. In this study, endophytic bacterial populations of two citrus cultivars-the resistant satsuma mandarin and the susceptible Newhall navel orange-were analyzed through high-throughput sequencing. The results showed that endophytic bacterial community of satsuma mandarin was more abundant than that of Newhall navel orange. In addition, bacterial abundance was the highest in the spring samples, followed by that in summer and winter samples, in both the varieties. In all samples, the predominant phyla were Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes; the major genera were Bacillus and Stenotrophomonas, and the main species was Bacillus subtilis. According to the analysis of the predominant bacteria in the two citrus cultivars, B. subtilis with potential antagonistic characteristics against Xcc existed universally in all samples. However, the susceptible Newhall navel oranges were abundant in Bacillus subtilis and had a relatively large number of canker-causing cooperative bacteria such as Stenotrophomonas. The results suggested that endophytic bacterial community of the two citrus cultivars had some differences based on the season or plant tissue, and these differences were mainly in the quantity of bacteria, affecting citrus canker disease occurrence. In conclusion, the differences in endophytic bacteria on citrus cultivars might be related to host resistance or susceptibility to citrus canker disease.


Assuntos
Citrus , Resistência à Doença , Microbiota , Xanthomonas , Citrus/microbiologia , Endófitos/classificação , Doenças das Plantas/microbiologia , Xanthomonas/patogenicidade
4.
Nat Commun ; 12(1): 4049, 2021 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-34193873

RESUMO

Xyloglucans are highly substituted and recalcitrant polysaccharides found in the primary cell walls of vascular plants, acting as a barrier against pathogens. Here, we reveal that the diverse and economically relevant Xanthomonas bacteria are endowed with a xyloglucan depolymerization machinery that is linked to pathogenesis. Using the citrus canker pathogen as a model organism, we show that this system encompasses distinctive glycoside hydrolases, a modular xyloglucan acetylesterase and specific membrane transporters, demonstrating that plant-associated bacteria employ distinct molecular strategies from commensal gut bacteria to cope with xyloglucans. Notably, the sugars released by this system elicit the expression of several key virulence factors, including the type III secretion system, a membrane-embedded apparatus to deliver effector proteins into the host cells. Together, these findings shed light on the molecular mechanisms underpinning the intricate enzymatic machinery of Xanthomonas to depolymerize xyloglucans and uncover a role for this system in signaling pathways driving pathogenesis.


Assuntos
Parede Celular/metabolismo , Citrus/microbiologia , Glucanos/metabolismo , Glicosídeo Hidrolases/metabolismo , Fatores de Virulência/genética , Xanthomonas/metabolismo , Xilanos/metabolismo , Proteínas de Bactérias/metabolismo , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Ativação Transcricional , Sistemas de Secreção Tipo III/metabolismo , Fatores de Virulência/metabolismo , Xanthomonas/genética , Xanthomonas/patogenicidade
5.
PLoS Pathog ; 17(7): e1009762, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34297775

RESUMO

Pathogens integrate multiple environmental signals to navigate the host and control the expression of virulence genes. In this process, small regulatory noncoding RNAs (sRNAs) may function in gene expression as post-transcriptional regulators. In this study, the sRNA Xonc3711 functioned in the response of the rice pathogen, Xanthomonas oryzae pv. oryzicola (Xoc), to oxidative stress. Xonc3711 repressed production of the DNA-binding protein Xoc_3982 by binding to the xoc_3982 mRNA within the coding region. Mutational analysis showed that regulation required an antisense interaction between Xonc3711 and xoc_3982 mRNA, and RNase E was needed for degradation of the xoc_3982 transcript. Deletion of Xonc3711 resulted in a lower tolerance to oxidative stress due to the repression of flagella-associated genes and reduced biofilm formation. Furthermore, ChIP-seq and electrophoretic mobility shift assays showed that Xoc_3982 repressed the transcription of effector xopC2, which contributes to virulence in Xoc BLS256. This study describes how sRNA Xonc3711 modulates multiple traits in Xoc via signals perceived from the external environment.


Assuntos
Estresse Oxidativo/fisiologia , RNA Antissenso/metabolismo , Xanthomonas/patogenicidade , Oryza/parasitologia , Doenças das Plantas/genética , Pequeno RNA não Traduzido , Virulência/genética , Xanthomonas/genética , Xanthomonas/metabolismo
6.
Sci Rep ; 11(1): 9445, 2021 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-33941790

RESUMO

Bacterial spot, caused by a group of Xanthomonads (Xanthomonas spp.), is a devastating disease. It can adversely affect the Capsicum annum productivity. Scientists are working on the role of antioxidants to meet this challenge. However, research is lacking on the role of antioxidant enzymes and their isoforms in the non-compatible pathogen and host plant interaction and resistance mechanisms in capsicum varieties. The present study was conducted to ascertain the defensive role of antioxidant enzymes and their isoforms in chilli varieties Hybrid, Desi, Serrano, Padron, and Shehzadi against bacterial spot disease-induced Xanthomonas sp. The seedlings were inoculated with bacterial pathogen @ 107 CFU/mL, and samples were harvested after regular intervals of 24 h for 4 days followed by inoculation. Total plant proteins were extracted in phosphate buffer and quantified through Bradford assay. The crude protein extracts were analyzed through quantitative enzymatic assays in order to document activity levels of various antioxidant enzymes, including peroxidase (POD), Catalase (CAT), Ascorbate peroxidase (APX), and Superoxide dismutase (SOD). Moreover, the profiles appearance of these enzymes and their isoforms were determined using native polyacrylamide gel electrophoresis (PAGE) analysis. These enzymes exhibited maximum activity in Hybrid (HiR) cultivar followed by Desi (R), Serrano (S), Padron, and Shehzadi (HS). Both the number of isoforms and expression levels were higher in highly resistant cultivars compared to susceptible and highly susceptible cultivars. The induction of POD, CAT, and SOD occurs at the early stages of growth in resistant Capsicum cultivars. At the same time, APX seems to make the second line of antioxidant defense mechanisms. We found that modulating antioxidant enzymes and isoforms activity at the seedling stage was an important mechanism for mitigating plant growth inhibition in the resistant ones.


Assuntos
Antioxidantes/metabolismo , Capsicum/microbiologia , Estresse Oxidativo/fisiologia , Doenças das Plantas/microbiologia , Estresse Fisiológico/fisiologia , Ascorbato Peroxidases/metabolismo , Capsicum/crescimento & desenvolvimento , Catalase/metabolismo , Peróxido de Hidrogênio/análise , Peroxidase/metabolismo , Proteínas de Plantas/análise , Isoformas de Proteínas/metabolismo , Superóxido Dismutase/metabolismo , Xanthomonas/patogenicidade
7.
Molecules ; 26(5)2021 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-33800893

RESUMO

In order to replace the huge amounts of copper salts used in citrus orchards, alternatives have been sought in the form of organic compounds of natural origin with activity against the causative agent of citrus canker, the phytopathogen Xanthomonas citri subsp. Citri. We synthesized a series of 4-alkoxy-1,2-benzene diols (alkyl-BDOs) using 1,2,4-benzenetriol (BTO) as a starting material through a three-step synthesis route and evaluated their suitability as antibacterial compounds. Our results show that alkyl ethers derived from 1,2,4-benzenetriol have bactericidal activity against X. citri, disrupting the bacterial cell membrane within 15 min. Alkyl-BDOs were also shown to remain active against the bacteria while in solution, and presented low toxicity to (human) MRC-5 cells. Therefore, we have demonstrated that 1,2,4-benzenetriol-a molecule that can be obtained from agricultural residues-is an adequate precursor for the synthesis of new compounds with activity against X. citri.


Assuntos
Antibacterianos/farmacologia , Derivados de Benzeno/farmacologia , Citrus/efeitos dos fármacos , Fibroblastos/efeitos dos fármacos , Doenças das Plantas/microbiologia , Folhas de Planta/efeitos dos fármacos , Xanthomonas/patogenicidade , Antibacterianos/química , Derivados de Benzeno/química , Proliferação de Células , Citrus/microbiologia , Fibroblastos/citologia , Humanos , Folhas de Planta/microbiologia
8.
Planta ; 253(5): 94, 2021 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-33830376

RESUMO

MAIN CONCLUSION: 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 (R2) 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.


Assuntos
Resistência à Doença/genética , Estudo de Associação Genômica Ampla , Oryza/genética , Oryza/microbiologia , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Xanthomonas/patogenicidade , Genes de Plantas/genética , Humanos , Melhoramento Vegetal , Polimorfismo de Nucleotídeo Único/genética
9.
Theor Appl Genet ; 134(7): 2129-2140, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33786652

RESUMO

KEY MESSAGE: Reducing the size of the I-3 introgression resulted in eliminating linkage-drag contributing to increased sensitivity to bacterial spot and reduced fruit size. The I-7 gene was determined to have no effect on bacterial spot or fruit size, and germplasm is now available with both the reduced I-3 introgression and I-7. Tomato (Solanum lycopersicum) production is increasingly threatened by Fusarium wilt race 3 (Fol3) caused by the soilborne fungus, Fusarium oxysporum f. sp. lycopersici. Although host resistance based on the I-3 gene is the most effective management strategy, I-3 is associated with detrimental traits including reduced fruit size and increased bacterial spot sensitivity. Previous research demonstrated the association with bacterial spot is not due to the I-3 gene, itself, and we hypothesize that reducing the size of the I-3 introgression will remedy this association. Cultivars with I-7, an additional Fol3 resistance gene, are available but are not widely used commercially, and it is unclear whether I-7 also has negative horticultural associations. To characterize the effect of I-3 on fruit size, segregating populations were developed and evaluated, revealing that the large I-3 introgression decreased fruit size by approximately 21%. We reduced the I-3 introgression from 5 to 140 kb through successive recombinant screening and crossing efforts. The reduced I-3 introgression and I-7 were then separately backcrossed into elite Florida breeding lines and evaluated for effects on bacterial spot sensitivity and fruit size across multiple seasons. The reduced I-3 introgression resulted in significantly less bacterial spot and larger fruit size than the large introgression, and it had no effect on these horticultural characteristics compared with Fol3 susceptibility. I-7 was also found to have no effect on these traits compared to Fol3 susceptibility. Together, these efforts support the development of superior Fol3-resistant cultivars and more durable resistance against this pathogen.


Assuntos
Resistência à Doença/genética , Fusarium/patogenicidade , Introgressão Genética , Lycopersicon esculentum/genética , Doenças das Plantas/genética , Frutas , Genes de Plantas , Ligação Genética , Lycopersicon esculentum/microbiologia , Melhoramento Vegetal , Doenças das Plantas/microbiologia , Xanthomonas/patogenicidade
10.
Plant Cell Environ ; 44(6): 1946-1960, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33675052

RESUMO

Plants rely on their microbiota for improving the nutritional status and environmental stress tolerance. Previous studies mainly focused on bipartite interactions (a plant challenged by a single microbe), while plant responses to multiple microbes have received limited attention. Here, we investigated local and systemic changes induced in wheat by two plant growth-promoting bacteria (PGPB), Azospirillum brasilense and Paraburkholderia graminis, either alone or together with an arbuscular mycorrhizal fungus (AMF). We conducted phenotypic, proteomic, and biochemical analyses to investigate bipartite (wheat-PGPB) and tripartite (wheat-PGPB-AMF) interactions, also upon a leaf pathogen infection. Results revealed that only AMF and A. brasilense promoted plant growth by activating photosynthesis and N assimilation which led to increased glucose and amino acid content. The bioprotective effect of the PGPB-AMF interactions on infected wheat plants depended on the PGPB-AMF combinations, which caused specific phenotypic and proteomic responses (elicitation of defense related proteins, immune response and jasmonic acid biosynthesis). In the whole, wheat responses strongly depended on the inoculum composition (single vs. multiple microbes) and the investigated organs (roots vs. leaf). Our findings showed that AMF is the best-performing microbe, suggesting its presence as the crucial one for synthetic microbial community development.


Assuntos
Fungos/fisiologia , Micorrizas/fisiologia , Proteínas de Plantas/metabolismo , Triticum/crescimento & desenvolvimento , Triticum/microbiologia , Inoculantes Agrícolas/fisiologia , Azospirillum brasilense , Burkholderiaceae , Interações Hospedeiro-Patógeno/fisiologia , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Raízes de Plantas/microbiologia , Proteômica/métodos , Triticum/metabolismo , Xanthomonas/patogenicidade
11.
Plant Cell Rep ; 40(5): 835-850, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33730215

RESUMO

KEY MESSAGE: The R89 is essential for the kinase activity of OsMPK6 which negatively regulates cell death and defense response in rice. Mitogen-activated protein kinase cascade plays critical roles in various vital activities, including the plant immune response, but the mechanisms remain elusive. Here, we identified and characterized a rice lesion mimic mutant osmpk6 which displayed hypersensitive response-like lesions in company with cell death and hydrogen peroxide hyperaccumulation. Map-based cloning and complementation demonstrated that a G702A single-base substitution in the second exon of OsMPK6 led to the lesion mimic phenotype of the osmpk6 mutant. OsMPK6 encodes a cytoplasm and nucleus-targeted mitogen-activated protein kinase and is expressed in the various organs. Compared with wild type, the osmpk6 mutant exhibited high resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo), likely due to the increased ROS production induced by flg22 and chitin and up-regulated expression of genes involved in pathogenesis, as well as activation of SA and JA signaling pathways after inoculation. By contrast, the OsMPK6-overexpression line (OE-1) was found to be susceptible to the bacterial pathogens, indicating that OsMPK6 negatively regulated Xoo resistance. Furthermore, the G702A single-base substitution caused a R89K mutation at both polypeptide substrate-binding site and active site of OsMPK6, and kinase activity assay revealed that the R89K mutation led to reduction of OsMPK6 activity, suggesting that the R89 is essential for the function of OsMPK6. Our findings provide insight into a vital role of the R89 of OsMPK6 in regulating cell death and defense response in rice.


Assuntos
Oryza/metabolismo , Oryza/microbiologia , Xanthomonas/patogenicidade , Quitina/genética , Quitina/metabolismo , Resistência à Doença/genética , Resistência à Doença/fisiologia , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/fisiologia , Oryza/genética , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Transdução de Sinais/genética , Transdução de Sinais/fisiologia
12.
Nat Commun ; 12(1): 1422, 2021 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-33658492

RESUMO

Trans-acyltransferase polyketide synthases (trans-AT PKSs) are bacterial multimodular enzymes that biosynthesize diverse pharmaceutically and ecologically important polyketides. A notable feature of this natural product class is the existence of chemical hybrids that combine core moieties from different polyketide structures. To understand the prevalence, biosynthetic basis, and evolutionary patterns of this phenomenon, we developed transPACT, a phylogenomic algorithm to automate global classification of trans-AT PKS modules across bacteria and applied it to 1782 trans-AT PKS gene clusters. These analyses reveal widespread exchange patterns suggesting recombination of extended PKS module series as an important mechanism for metabolic diversification in this natural product class. For three plant-associated bacteria, i.e., the root colonizer Gynuella sunshinyii and the pathogens Xanthomonas cannabis and Pseudomonas syringae, we demonstrate the utility of this computational approach for uncovering cryptic relationships between polyketides, accelerating polyketide mining from fragmented genome sequences, and discovering polyketide variants with conserved moieties of interest. As natural combinatorial hybrids are rare among the more commonly studied cis-AT PKSs, this study paves the way towards evolutionarily informed, rational PKS engineering to produce chimeric trans-AT PKS-derived polyketides.


Assuntos
Aciltransferases/genética , Proteínas de Bactérias/genética , Filogenia , Policetídeo Sintases/genética , Policetídeos/metabolismo , Aciltransferases/metabolismo , Algoritmos , Arabidopsis/microbiologia , Proteínas de Bactérias/metabolismo , Evolução Molecular , Genoma Bacteriano , Células HeLa , Humanos , Lactonas/metabolismo , Macrolídeos/metabolismo , Família Multigênica , Piperidonas/química , Plantas/microbiologia , Policetídeo Sintases/metabolismo , Policetídeos/química , Pseudomonas syringae/metabolismo , Xanthomonas/metabolismo , Xanthomonas/patogenicidade
13.
Mol Plant ; 14(4): 620-632, 2021 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-33450368

RESUMO

Mitogen-activated protein kinase (MAPK) cascades regulate a myriad of plant biological processes, including disease resistance. Plant genomes encode a large number of MAPK kinase kinases (MAPKKKs) that can be divided into two subfamilies, namely MEKK-like kinases and Raf-like kinases. Thus far, the functions of MEKK-like MAPKKKs have been relatively well characterized, but the roles of Raf-like MAPKKKs in plant MAPK cascades remain less understood. Here, we report the role of OsEDR1, a Raf-like MAPKKK, in the regulation of the MAPK cascade in rice response to the bacterial pathogen Xanthomonas oryzae pv. oryzicola (Xoc). We found that OsEDR1 inhibits OsMPKK10.2 (a MAPK kinase) activity through physical interaction. Upon Xoc infection, OsMPKK10.2 is phosphorylated at S304 to activate OsMPK6 (a MAPK). Interestingly, activated OsMPK6 phosphorylates OsEDR1 at S861, which destabilizes OsEDR1 and thus releases the inhibition of OsMPKK10.2, leading to increased OsMPKK10.2 activity and enhanced resistance of rice plants to Xoc. Taken together, these results provide new insights into the functions of Raf-like kinases in the regulation of the MAPK cascade in plant immunity.


Assuntos
Oryza/microbiologia , Doenças das Plantas/microbiologia , Plantas Geneticamente Modificadas/microbiologia , Resistência à Doença/genética , Regulação da Expressão Gênica de Plantas , Fosforilação/genética , Imunidade Vegetal/genética , Imunidade Vegetal/fisiologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Xanthomonas/patogenicidade
15.
Sci Rep ; 11(1): 2034, 2021 01 21.
Artigo em Inglês | MEDLINE | ID: mdl-33479414

RESUMO

Legume plants form a root-nodule symbiosis with rhizobia. This symbiosis establishment generally relies on rhizobium-produced Nod factors (NFs) and their perception by leguminous receptors (NFRs) that trigger nodulation. However, certain rhizobia hijack leguminous nodulation signalling via their type III secretion system, which functions in pathogenic bacteria to deliver effector proteins into host cells. Here, we report that rhizobia use pathogenic-like effectors to hijack legume nodulation signalling. The rhizobial effector Bel2-5 resembles the XopD effector of the plant pathogen Xanthomonas campestris and could induce nitrogen-fixing nodules on soybean nfr mutant. The soybean root transcriptome revealed that Bel2-5 induces expression of cytokinin-related genes, which are important for nodule organogenesis and represses ethylene- and defense-related genes that are deleterious to nodulation. Remarkably, Bel2-5 introduction into a strain unable to nodulate soybean mutant affected in NF perception conferred nodulation ability. Our findings show that rhizobia employ and have customized pathogenic effectors to promote leguminous nodulation signalling.


Assuntos
Bradyrhizobium/genética , Rhizobium/genética , Nódulos Radiculares de Plantas/genética , Soja/genética , Fabaceae/genética , Fabaceae/microbiologia , Regulação da Expressão Gênica de Plantas/genética , Nodulação/genética , Raízes de Plantas/genética , Raízes de Plantas/microbiologia , Rhizobium/patogenicidade , Nódulos Radiculares de Plantas/crescimento & desenvolvimento , Transdução de Sinais/genética , Soja/crescimento & desenvolvimento , Soja/microbiologia , Simbiose/genética , Xanthomonas/genética , Xanthomonas/patogenicidade
16.
Mol Plant Pathol ; 22(4): 480-492, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33486879

RESUMO

Xanthomonas oryzae pathovars oryzae (Xoo) and oryzicola (Xoc) infect rice, causing bacterial blight and bacterial leaf streak, respectively, which are two economically important bacterial diseases in paddy fields. The interactions of Xoo and Xoc with rice can be used as models for studying fundamental aspects of bacterial pathogenesis and host tissue specificity. However, an improved vector system for gene expression analysis is desired for Xoo and Xoc because some broad host range vectors that can replicate stably in X. oryzae pathovars are low-copy number plasmids. To overcome this limitation, we developed a modular plasmid assembly system to transfer the functional DNA modules from the entry vectors into the pHM1-derived backbone vectors on a high-copy number basis. We demonstrated the feasibility of our vector system for protein detection, and quantification of virulence gene expression under laboratory conditions and in association with host rice and nonhost tobacco cells. This system also allows execution of a mutant complementation equivalent to the single-copy chromosomal integration system and tracing of pathogens in rice leaf. Based on this assembly system, we constructed a series of protein expression and promoter-probe vectors suitable for classical double restriction enzyme cloning. These vector systems enable cloning of all genes or promoters of interest from Xoo and Xoc strains. Our modular assembly system represents a versatile and highly efficient toolkit for gene expression analysis that will accelerate studies on interactions of X. oryzae with rice.


Assuntos
Proteínas de Bactérias/metabolismo , Oryza/microbiologia , Doenças das Plantas/microbiologia , Xanthomonas/genética , Proteínas de Bactérias/genética , Expressão Gênica , Vetores Genéticos/genética , Folhas de Planta/microbiologia , Plasmídeos/genética , Regiões Promotoras Genéticas/genética , Tabaco/microbiologia , Virulência , Xanthomonas/patogenicidade , Xanthomonas/fisiologia
17.
BMC Microbiol ; 21(1): 14, 2021 01 06.
Artigo em Inglês | MEDLINE | ID: mdl-33407123

RESUMO

BACKGROUND: The type VI protein secretion system (T6SS) is important in diverse cellular processes in Gram-negative bacteria, including interactions with other bacteria and with eukaryotic hosts. In this study we analyze the evolution of the T6SS in the genus Xanthomonas and evaluate its importance of the T6SS for virulence and in vitro motility in Xanthomonas phaseoli pv. manihotis (Xpm), the causal agent of bacterial blight in cassava (Manihot esculenta). We delineate the organization of the T6SS gene clusters in Xanthomonas and then characterize proteins of this secretion system in Xpm strain CIO151. RESULTS: We describe the presence of three different clusters in the genus Xanthomonas that vary in their organization and degree of synteny between species. Using a gene knockout strategy, we also found that vgrG and hcp are required for maximal aggressiveness of Xpm on cassava plants while clpV is important for both motility and maximal aggressiveness. CONCLUSION: We characterized the T6SS in 15 different strains in Xanthomonas and our phylogenetic analyses suggest that the T6SS might have been acquired by a very ancient event of horizontal gene transfer and maintained through evolution, hinting at their importance for the adaptation of Xanthomonas to their hosts. Finally, we demonstrated that the T6SS of Xpm is functional, and significantly contributes to virulence and motility. This is the first experimental study that demonstrates the role of the T6SS in the Xpm-cassava interaction and the T6SS organization in the genus Xanthomonas.


Assuntos
Biologia Computacional/métodos , Sistemas de Secreção Tipo VI/genética , Xanthomonas/patogenicidade , Técnicas de Inativação de Genes , Transferência Genética Horizontal , Mutação , Filogenia , Análise de Sequência de DNA , Virulência , Xanthomonas/classificação , Xanthomonas/genética , Xanthomonas/fisiologia
18.
PLoS Genet ; 17(1): e1009310, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33465093

RESUMO

Transcription activator-like effectors (TALEs) are virulence factors of Xanthomonas that induce the expression of host susceptibility (S) genes by specifically binding to effector binding elements (EBEs) in their promoter regions. The DNA binding specificity of TALEs is dictated by their tandem repeat regions, which are highly variable between different TALEs. Mutation of the EBEs of S genes is being utilized as a key strategy to generate resistant crops against TALE-dependent pathogens. However, TALE adaptations through rearrangement of their repeat regions is a potential obstacle for successful implementation of this strategy. We investigated the consequences of TALE adaptations in the citrus pathogen Xanthomonas citri subsp. citri (Xcc), in which PthA4 is the TALE required for pathogenicity, whereas CsLOB1 is the corresponding susceptibility gene, on host resistance. Seven TALEs, containing two-to-nine mismatching-repeats to the EBEPthA4 that were unable to induce CsLOB1 expression, were introduced into Xcc pthA4:Tn5 and adaptation was simulated by repeated inoculations into and isolations from sweet orange for a duration of 30 cycles. While initially all strains failed to promote disease, symptoms started to appear between 9-28 passages in four TALEs, which originally harbored two-to-five mismatches. Sequence analysis of adapted TALEs identified deletions and mutations within the TALE repeat regions which enhanced putative affinity to the CsLOB1 promoter. Sequence analyses suggest that TALEs adaptations result from recombinations between repeats of the TALEs. Reintroduction of these adapted TALEs into Xcc pthA4:Tn5 restored the ability to induce the expression of CsLOB1, promote disease symptoms and colonize host plants. TALEs harboring seven-to-nine mismatches were unable to adapt to overcome the incompatible interaction. Our study experimentally documented TALE adaptations to incompatible EBE and provided strategic guidance for generation of disease resistant crops against TALE-dependent pathogens.


Assuntos
Interações Hospedeiro-Patógeno/genética , Efetores Semelhantes a Ativadores de Transcrição/genética , Fatores de Virulência/genética , Xanthomonas/genética , Proteínas de Bactérias/genética , Citrus/genética , Citrus/microbiologia , Regulação da Expressão Gênica de Plantas/genética , Mutação/genética , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Proteínas de Plantas/genética , Regiões Promotoras Genéticas/genética , Xanthomonas/patogenicidade
19.
PLoS Genet ; 17(1): e1009316, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33493197

RESUMO

Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is one of the most devastating diseases in citrus industry worldwide. Most citrus cultivars such as sweet orange are susceptible to canker disease. Here, we utilized wild citrus to identify canker-resistant germplasms, and found that Atalantia buxifolia, a primitive (distant-wild) citrus, exhibited remarkable resistance to canker disease. Although the susceptibility gene LATERAL ORGAN BOUNDARIES 1 (LOB1) could also be induced in Atalantia after canker infection, the induction extent was far lower than that in sweet orange. In addition, three of amino acids encoded by transcription factor TFIIAγ in Atalantia (AbTFIIAγ) exhibited difference from those in sweet orange (CsTFIIAγ) which could stabilize the interaction between effector PthA4 and effector binding element (EBE) of LOB1 promoter. The mutation of AbTFIIAγ did not change its interaction with transcription factor binding motifs (TFBs). However, the AbTFIIAγ could hardly support the LOB1 expression induced by the PthA4. In addition, the activity of AbLOB1 promoter was significantly lower than that of CsLOB1 under the induction by PthA4. Our results demonstrate that natural variations of AbTFIIAγ and effector binding element (EBE) in the AbLOB1 promoter are crucial for the canker disease resistance of Atalantia. The natural mutations of AbTFIIAγ gene and AbLOB1 promoter in Atalantia provide candidate targets for improving the resistance to citrus canker disease.


Assuntos
Resistência à Doença/genética , Doenças das Plantas/genética , Rutaceae/genética , Fator de Transcrição TFIIA/genética , Citrus/genética , Citrus/crescimento & desenvolvimento , Citrus/microbiologia , Regulação da Expressão Gênica de Plantas , Mutação/genética , Doenças das Plantas/microbiologia , Proteínas de Plantas/genética , Regiões Promotoras Genéticas/genética , Ligação Proteica/genética , Rutaceae/crescimento & desenvolvimento , Rutaceae/microbiologia , Xanthomonas/genética , Xanthomonas/patogenicidade
20.
PLoS Pathog ; 17(1): e1009175, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33428681

RESUMO

The zig-zag model of host-pathogen interaction describes the relative strength of defense response across a spectrum of pathogen-induced plant phenotypes. A stronger defense response results in increased resistance. Here, we investigate the strength of pathogen virulence during disease and place these findings in the context of the zig-zag model. Xanthomonas vasicola pv. holcicola (Xvh) causes sorghum bacterial leaf streak. Despite being widespread, this disease has not been described in detail at the molecular level. We divided diverse sorghum genotypes into three groups based on disease symptoms: water-soaked lesions, red lesions, and resistance. Bacterial growth assays confirmed that these three phenotypes represent a range of resistance and susceptibility. To simultaneously reveal defense and virulence responses across the spectrum of disease phenotypes, we performed dual RNA-seq on Xvh-infected sorghum. Consistent with the zig-zag model, the expression of plant defense-related genes was strongest in the resistance interaction. Surprisingly, bacterial virulence genes related to the type III secretion system (T3SS) and type III effectors (T3Es) were also most highly expressed in the resistance interaction. This expression pattern was observed at multiple time points within the sorghum-Xvh pathosystem. Further, a similar expression pattern was observed in Arabidopsis infected with Pseudomonas syringae for effector-triggered immunity via AvrRps4 but not AvrRpt2. Specific metabolites were able to repress the Xvh virulence response in vitro and in planta suggesting a possible signaling mechanism. Taken together, these findings reveal multiple permutations of the continually evolving host-pathogen arms race from the perspective of host defense and pathogen virulence responses.


Assuntos
Regulação Bacteriana da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Interações Hospedeiro-Patógeno/imunologia , Doenças das Plantas/microbiologia , Sorghum/microbiologia , Virulência , Xanthomonas/patogenicidade , Doenças das Plantas/genética , Doenças das Plantas/imunologia , Sorghum/genética , Sorghum/imunologia , Transcriptoma , Xanthomonas/genética , Xanthomonas/imunologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...