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1.
Environ Microbiol Rep ; 10(5): 522-531, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29687657

RESUMO

Expression of hrp (hypersensitive reaction and pathogenicity) genes inside the host is crucial for virulence of phytopathogenic bacteria. The hrp genes encode components of type3 secretion system (T3SS), HR elicitors and several regulators, which are involved in the co-ordinated expression of hrp genes in the host environment and in hrp inducing chemically defined medium. However, little is known about specific host or environmental factors which may play a role in the induction of hrp gene expression. In this study, we show that iron-limiting condition elicits induced expression of hrp genes, including type3 secretion system (T3SS) and effectors (T3E). Expression analysis using qRT-PCR and promoter probe strains suggest significant induction in the expression of Hrp and T3S-associated genes of Xanthomonas campestris pv. campestris (Xcc) under low-iron condition, and is suppressed by exogenous supplementation of iron. Furthermore, we show that with exogenous iron supplementation, wild type Xcc exhibited reduced disease symptoms in host-plant, and exhibited significant reduction in HR and callose deposition in the non-host plants. Xanthomonas oryzae and oryzicola pathovars also exhibited the iron affect, albeit to a lesser extend compared with the Xcc. Overall, our results suggest that low-iron condition inside the host may play a crucial role in pathogenicity.


Assuntos
Proteínas de Bactérias/genética , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Ferro/farmacologia , Xanthomonas/patogenicidade , Deleção de Genes , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/microbiologia , Regiões Promotoras Genéticas , Virulência/efeitos dos fármacos , Virulência/genética , Xanthomonas/genética , Xanthomonas/crescimento & desenvolvimento
2.
Mol Plant Pathol ; 18(7): 949-962, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-27348422

RESUMO

Xanthomonas campestris pv. campestris causes black rot, a serious disease of crucifers. Xanthomonads encode a siderophore biosynthesis and uptake gene cluster xss (Xanthomonas siderophore synthesis) involved in the production of a vibrioferrin-type siderophore. However, little is known about the role of the siderophore in the iron uptake and virulence of X. campestris pv. campestris. In this study, we show that X. campestris pv. campestris produces an α-hydroxycarboxylate-type siderophore (named xanthoferrin), which is required for growth under low-iron conditions and for optimum virulence. A mutation in the siderophore synthesis xssA gene causes deficiency in siderophore production and growth under low-iron conditions. In contrast, the siderophore utilization ΔxsuA mutant is able to produce siderophore, but exhibits a defect in the utilization of the siderophore-iron complex. Our radiolabelled iron uptake studies confirm that the ΔxssA and ΔxsuA mutants exhibit defects in ferric iron (Fe3+ ) uptake. The ΔxssA mutant is able to utilize and transport the exogenous xanthoferrin-Fe3+ complex; in contrast, the siderophore utilization or uptake mutant ΔxsuA exhibits defects in siderophore uptake. Expression analysis of the xss operon using a chromosomal gusA fusion indicates that the xss operon is expressed during in planta growth and under low-iron conditions. Furthermore, exogenous iron supplementation in cabbage leaves rescues the in planta growth deficiency of ΔxssA and ΔxsuA mutants. Our study reveals that the siderophore xanthoferrin is an important virulence factor of X. campestris pv. campestris which promotes in planta growth by the sequestration of Fe3+ .


Assuntos
Brassica/microbiologia , Ácidos Carboxílicos/metabolismo , Sideróforos/metabolismo , Xanthomonas campestris/crescimento & desenvolvimento , Xanthomonas campestris/patogenicidade , Proteínas de Bactérias/metabolismo , Genes Bacterianos , Espaço Intracelular/metabolismo , Ferro/metabolismo , Ferro/farmacologia , Família Multigênica , Mutação/genética , Óperon/genética , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/microbiologia , Sideróforos/biossíntese , Virulência/efeitos dos fármacos , Xanthomonas campestris/genética
3.
Mol Microbiol ; 96(4): 708-27, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25656587

RESUMO

Cell-cell communication mediated by diffusible signal factor (DSF) plays an important role in virulence of several Xanthomonas group of plant pathogens. In the bacterial pathogen of rice, Xanthomonas oryzae pv. oryzicola, DSF is required for virulence and in planta growth. In order to understand the role of DSF in promoting in planta growth and virulence, we have characterized the DSF deficient mutant of X. oryzae pv. oryzicola. Mutant analysis by expression analysis, radiolabelled iron uptake studies and growth under low-iron conditions indicated that DSF positively regulates ferric iron uptake. Further, the DSF deficient mutant of X. oryzae pv. oryzicola exhibited a reduced capacity to use ferric form of iron for growth under low-iron conditions. Exogenous iron supplementation in the rice leaves rescued the in planta growth deficiency of the DSF deficient mutant. These data suggest that DSF promotes in planta growth of X. oryzae pv. oryzicola by positively regulating functions involved in ferric iron uptake which is important for its virulence. Our results also indicate that requirement of iron uptake strategies to utilize either Fe(3+) or Fe(2+) form of iron for colonization may vary substantially among closely related members of the Xanthomonas group of plant pathogens.


Assuntos
Compostos Férricos/metabolismo , Ácidos Láuricos/metabolismo , Interações Microbianas , Oryza/microbiologia , Transdução de Sinais , Xanthomonas/metabolismo , Xanthomonas/patogenicidade , Citratos/biossíntese , Compostos Férricos/farmacologia , Regulação Bacteriana da Expressão Gênica , Ligases/genética , Ligases/metabolismo , Mutação , Folhas de Planta/microbiologia , Pirrolidinonas , Virulência/genética , Xanthomonas/genética , Xanthomonas/crescimento & desenvolvimento
4.
Mol Plant Microbe Interact ; 16(11): 973-82, 2003 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-14601665

RESUMO

Xanthomonas oryzae pv. oryzae causes bacterial leaf blight, a serious disease of rice. We have identified a novel virulence deficient mutant (BXO1691) of X. oryzae pv. oryzae that has a Tn5 insertion in an open reading frame (phyA; putative phytase A) encoding a 373-amino acid (aa) protein containing a 28-aa predicted signal peptide. Extracellular protein profiles revealed that a 38-kDa band is absent in phyA mutants as compared with phyA+ strains. A BLAST search with phyA and its deduced polypeptide sequence indicated significant similarity with conserved hypothetical proteins in Xanthomonas axonopodis pv. citri and Xanthomonas campestris pv. campestris and limited homology to secreted phytases of Bacillus species. Homology modeling with a Bacillus phytase as the template suggests that the PhyA protein has a similar six-bladed beta-propeller architecture and exhibits conservation of certain critical active site residues. Phytases are enzymes that are involved in degradation of phytic acid (inositol hexaphosphate), a stored form of phosphate in plants. The phyA mutants exhibit a growth deficiency in media containing phytic acid as a sole phosphate source. Exogenous phosphate supplementation promotes migration of phyA X. oryzae pv. oryzae mutants in rice leaves. These results suggest that the virulence deficiency of phyA mutants is, at least in part, due to inability to use host phytic acid as a source of phosphate. phyA-like genes have not been previously reported to be involved in the virulence of any plant pathogenic bacterium.


Assuntos
Fosfatos/metabolismo , Ácido Fítico/metabolismo , Fitocromo/genética , Fitocromo/metabolismo , Xanthomonas/crescimento & desenvolvimento , Xanthomonas/patogenicidade , Sequência de Bases , Southern Blotting , Clonagem Molecular , Escherichia coli/genética , Dados de Sequência Molecular , Oryza/efeitos dos fármacos , Oryza/crescimento & desenvolvimento , Oryza/microbiologia , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/isolamento & purificação , Fitocromo A , Doenças das Plantas/microbiologia , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/microbiologia , Plasmídeos/genética , Deleção de Sequência , Virulência/genética , Xanthomonas/genética
5.
Mol Plant Microbe Interact ; 15(5): 463-71, 2002 May.
Artigo em Inglês | MEDLINE | ID: mdl-12036277

RESUMO

Xanthomonas oryzae pv. oryzae causes bacterial leaf blight, a serious disease of rice. In the related bacterium Xanthomonas campestris pv. campestris, the rpfF gene is involved in production of a diffusible extracellular factor (DSF) that positively regulates synthesis of virulence-associated functions like extracellular polysaccharide (EPS) and extracellular enzymes. Transposon insertions in the rpfF homolog of X. oryzae pv. oryzae are deficient for virulence and production of a DSF but are proficient for EPS and extracellular enzyme production. The rpfF X. oryzae pv. oryzae mutants exhibit an unusual tetracycline susceptibility phenotype in which exogenous iron supplementation is required for phenotypic expression of a tetracycline resistance determinant that is encoded on an introduced plasmid. The rpfF X. oryzae pv. oryzae mutants also overproduce one or more siderophores and exhibit a growth deficiency under low iron conditions as well as in the presence of reducing agents that are expected to promote the conversion of Fe+3 to Fe+2. Exogenous iron supplementation promotes migration of rpfF X. oryzae pv. oryzae mutants in rice leaves. The results suggest that rpfF may be involved in controlling an iron-uptake system of X. oryzae pv. oryzae and that an inability to cope with the conditions of low iron availability in the host may be the reason for the virulence deficiency of the rpfF X. oryzae pv. oryzae mutants.


Assuntos
Proteínas de Bactérias/genética , Ferro/farmacologia , Xanthomonas/genética , Antibacterianos/farmacologia , Proteínas de Bactérias/metabolismo , Divisão Celular/efeitos dos fármacos , Divisão Celular/genética , Teste de Complementação Genética , Dados de Sequência Molecular , Mutação , Oryza/microbiologia , Fenótipo , Doenças das Plantas/microbiologia , Folhas de Planta/microbiologia , Sideróforos/biossíntese , Transdução de Sinais/genética , Tetraciclina/farmacologia , Virulência/genética , Xanthomonas/efeitos dos fármacos , Xanthomonas/patogenicidade
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