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Investigation of the chemical structure and biological activity of oligosaccharides isolated from rough-type Xanthomonas campestris pv. campestris B100 lipopolysaccharide.

J Endotoxin Res. 2007;13(2):101-8

Authors: Kaczyński Z, Braun S, Lindner B, Niehaus K, Holst O

The rough-type lipopolysaccharide (LPS) of the phytopathogenic bacterium Xanthomonas campestris pv. campestris B 100 was isolated utilizing the hot phenol-water method and successively de-acylated by treatment with hydrazine and hot potassium hydroxide. Four compounds were separated by preparative high-performance anion-exchange chromatography and studied by sugar analysis and by 1D and 2D homonuclear and heteronuclear (1)H-, (13)C- and (31)P-NMR spectroscopy as well as ESI FT-MS. The two main products were a heptasaccharide and a pentasaccharide of the structures alpha-D-Manp-(1-->3)-alpha-D-Man p-(1-->4)-beta-D-Glcp-(1-->4)-alpha-D-Manp-3P -(1-->5)-alpha-Kdo-(2-->6)-beta-D-GlcpN-4P-(1-->6)-alpha-D-Glc pN-1P (1) and beta-D-Glcp-(1-->4)-alpha-D-Man p-3P-(1-->5)-alpha-Kdo-(2-->6)-beta-D-GlcpN-4 P-(1-->6)-alpha-D-GlcpN-1P (2), respectively. The products in smaller amounts were a heptasaccharide and pentasaccharide possessing the above structures plus a phosphate group at C-4 of the Kdo residue (compounds 3 and 4). Both, heptasaccharide 1 and pentasaccharide 2 were able to induce an oxidative burst in cell cultures of the non-host plant tobacco.

PMID: 17621551 [PubMed - in process]

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Three New Loci of Insertion Element IS1112 in Chinese Strains of Xanthomonas oryzae pv. oryzae.

J Microbiol. 2007 Jun;45(3):219-26

Authors: Xie J, Wang X, Li F, Peng Y, Zhou G

Insertion sequence IS1112 is a repetitive element with a relatively high number of copies in Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial blight of rice (Oryza sativa L.). Three new loci of IS1112 were identified in seven Chinese strains of Xoo using a single oligonucleotide primer J3; 5'-GCTCAGGTCAGGTGGCCTGG-3' by insertion-sequence-based polymerase chain reaction (IS-PCR). Among the three new loci of IS1112, two were located in the open-reading frame region of genes fhuA and cirA, which encode TonB-dependent receptors, and the third in ISXo2, another type of insertion sequence in Xoo genome. Three variants of IS1112 were identified in those three loci based on their sequence similarities: two were identical to IS1112a and IS1112b, reported in strain PXO86 from the Philippines, while the third was a new member of IS1112, defined as IS1112d. Inserting IS1112 in gene fhuA caused three bases, GGT, to be duplicated at the target site, but inserting it in gene cirA did not cause any duplication in the target site. The diversity of IS1112 sequence and insertion loci in Xoo genome and their potential effects are discussed.

PMID: 17618227 [PubMed - in process]

Science Daily (press release)New Dry Edible Bean Resists Bacterial Disease
Science Daily (press release) - Jul 10, 2007
(Credit: Photo by Stephen Ausmus) Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops ...

Science Daily (press release)New Dry Edible Bean Resists Bacterial Disease
Science Daily (press release) - Jul 10, 2007
(Credit: Photo by Stephen Ausmus) Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops ...

Science Daily (press release)New Dry Edible Bean Resists Bacterial Disease
Science Daily (press release) - Jul 10, 2007
(Credit: Photo by Stephen Ausmus) Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops ...

Science Daily (press release)New Dry Edible Bean Resists Bacterial Disease
Science Daily (press release) - Jul 10, 2007
(Credit: Photo by Stephen Ausmus) Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops ...

Science Daily (press release)New Dry Edible Bean Resists Bacterial Disease
Science Daily (press release) - Jul 10, 2007
(Credit: Photo by Stephen Ausmus) Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops ...

Science Daily (press release)New Dry Edible Bean Resists Bacterial Disease
Science Daily (press release) - Jul 10, 2007
(Credit: Photo by Stephen Ausmus) Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops ...

Science Daily (press release)New Dry Edible Bean Resists Bacterial Disease
Science Daily (press release) - 23 hours ago
(Credit: Photo by Stephen Ausmus) Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops ...

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The 9-lipoxygenase GhLOX1 gene is associated with the hypersensitive reaction of cotton Gossypium hirsutum to Xanthomonas campestris pv malvacearum.

Plant Physiol Biochem. 2007 May 18;

Authors: Marmey P, Jalloul A, Alhamdia M, Assigbetse K, Cacas JL, Voloudakis AE, Champion A, Clerivet A, Montillet JL, Nicole M

Hypersensitive reaction (HR) cell death of cotton to the incompatible race 18 from Xanthomonas campestris pathovar malvacearum (Xcm) is associated with 9S-lipoxygenase activity (LOX) responsible for lipid peroxidation. Here, we report the cloning of cotton (Gossypium hirsutum L.) LOX gene (GhLOX1) and the sequencing of its promoter. GhLOX1 was found to be highly expressed during Xcm induced HR. Sequence analysis showed that GhLOX1 is a putative 9-LOX, and GhLOX1 promoter contains SA and JA responsive elements. Investigation on LOX signalisation on cotyledons infiltrated with salicylic acid (SA), or incubated with methyl-jasmonate (MeJA) revealed that both treatments induced LOX activity and GhLOX1 gene expression. HR-like symptoms were observed when LOX substrates were then injected in treated (MeJA and SA) cotyledons or when Xcm compatible race 20 was inoculated on MeJA treated cotyledons. Together these results support the fact that GhLOX1 encodes a 9 LOX whose activity would be involved in cell death during cotton HR.

PMID: 17611116 [PubMed - as supplied by publisher]

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Bacterial Cyclic {beta}-(1,2)-Glucan Acts in Systemic Suppression of Plant Immune Responses.

Plant Cell. 2007 Jun 29;

Authors: Rigano LA, Payette C, Brouillard G, Marano MR, Abramowicz L, Torres PS, Yun M, Castagnaro AP, Oirdi ME, Dufour V, Malamud F, Dow JM, Bouarab K, Vojnov AA

Although cyclic glucans have been shown to be important for a number of symbiotic and pathogenic bacterium-plant interactions, their precise roles are unclear. Here, we examined the role of cyclic beta-(1,2)-glucan in the virulence of the black rot pathogen Xanthomonas campestris pv campestris (Xcc). Disruption of the Xcc nodule development B (ndvB) gene, which encodes a glycosyltransferase required for cyclic glucan synthesis, generated a mutant that failed to synthesize extracellular cyclic beta-(1,2)-glucan and was compromised in virulence in the model plants Arabidopsis thaliana and Nicotiana benthamiana. Infection of the mutant bacterium in N. benthamiana was associated with enhanced callose deposition and earlier expression of the PATHOGENESIS-RELATED1 (PR-1) gene. Application of purified cyclic beta-(1,2)-glucan prior to inoculation of the ndvB mutant suppressed the accumulation of callose deposition and the expression of PR-1 in N. benthamiana and restored virulence in both N. benthamiana and Arabidopsis plants. These effects were seen when cyclic glucan and bacteria were applied either to the same or to different leaves. Cyclic beta-(1,2)-glucan-induced systemic suppression was associated with the transport of the molecule throughout the plant. Systemic suppression is a novel counterdefensive strategy that may facilitate pathogen spread in plants and may have important implications for the understanding of plant-pathogen coevolution and for the development of phytoprotection measures.

PMID: 17601826 [PubMed - as supplied by publisher]

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Recessive resistance genes and the Oryza sativa-Xanthomonas oryzae pv. oryzae pathosystem.

Mol Plant Microbe Interact. 2007 Jul;20(7):731-9

Authors: Iyer-Pascuzzi AS, McCouch SR

Though recessive resistance is well-studied in viral systems, little is understood regarding the phenomenon in plant-bacterial interactions. The Oryza sativa-Xanthomonas oryzae pv. orzyae pathosystem provides an excellent opportunity to examine recessive resistance in plant-bacterial interactions, in which nine of 30 documented resistance (R) genes are recessively inherited. Infestations of X. oryzae pv. oryzae, the causal agent of bacterial blight, result in significant crop loss and damage throughout South and Southeast Asia. Two recently cloned novel recessive R genes, xa5 and xa13, have yielded insights to this system. Like their viral counterparts, these bacterial recessive R gene products do not conform to the five commonly described classes of R proteins. New findings suggest that such genes may more aptly be viewed as mutations in dominant susceptibility alleles and may also function in a gene-for-gene manner. In this review, we discuss recent accomplishments in the understanding of recessively inherited R genes in the rice-bacterial blight pathosystem and suggest a new model for the function of recessive resistance in plant-bacterial interactions.

PMID: 17601161 [PubMed - in process]

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A single mutation in the active site swaps the substrate specificity of N-acetyl-L-ornithine transcarbamylase and N-succinyl-L-ornithine transcarbamylase.

Protein Sci. 2007 Jun 28;

Authors: Shi D, Yu X, Cabrera-Luque J, Chen TY, Roth L, Morizono H, Allewell NM, Tuchman M

Transcarbamylases catalyze the transfer of the carbamyl group from carbamyl phosphate (CP) to an amino group of a second substrate such as aspartate, ornithine, or putrescine. Previously, structural determination of a transcarbamylase from Xanthomonas campestris led to the discovery of a novel N-acetylornithine transcarbamylase (AOTCase) that catalyzes the carbamylation of N-acetylornithine. Recently, a novel N-succinylornithine transcarbamylase (SOTCase) from Bacteroides fragilis was identified. Structural comparisons of AOTCase from X. campestris and SOTCase from B. fragilis revealed that residue Glu92 (X. campestris numbering) plays a critical role in distinguishing AOTCase from SOTCase. Enzymatic assays of E92P, E92S, E92V, and E92A mutants of AOTCase demonstrate that each of these mutations converts the AOTCase to an SOTCase. Similarly, the P90E mutation in B. fragilis SOTCase (equivalent to E92 in X. campestris AOTCase) converts the SOTCase to AOTCase. Hence, a single amino acid substitution is sufficient to swap the substrate specificities of AOTCase and SOTCase. X-ray crystal structures of these mutants in complexes with CP and N-acetyl-L-norvaline (an analog of N-acetyl-L-ornithine) or N-succinyl-L-norvaline (an analog of N-succinyl-L-ornithine) substantiate this conversion. In addition to Glu92 (X. campestris numbering), other residues such as Asn185 and Lys30 in AOTCase, which are involved in binding substrates through bridging water molecules, help to define the substrate specificity of AOTCase. These results provide the correct annotation (AOTCase or SOTCase) for a set of the transcarbamylase-like proteins that have been erroneously annotated as ornithine transcarbamylase (OTCase, EC 2.1.3.3).

PMID: 17600144 [PubMed - as supplied by publisher]

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Characterization of the first angiotensin-converting like enzyme in bacteria: Ancestor ACE is already active.

Gene. 2007 Jun 2;

Authors: Rivière G, Michaud A, Corradi HR, Sturrock ED, Ravi Acharya K, Cogez V, Bohin JP, Vieau D, Corvol P

Angiotensin-converting enzyme (ACE) is a metallopeptidase that converts angiotensin I into angiotensin II. ACE is crucial in the control of cardiovascular and renal homeostasis and fertility in mammals. In vertebrates, both transmembrane and soluble ACE, containing one or two active sites, have been characterized. So far, only soluble, single domain ACEs from invertebrates have been cloned, and these have been implicated in reproduction in insects. Furthermore, an ACE-related carboxypeptidase was recently characterized in Leishmania, a unicellular eukaryote, suggesting the existence of ACE in more distant organisms. Interestingly, in silico databank analysis revealed that bacterial DNA sequences could encode putative ACE-like proteins, strikingly similar to vertebrates' enzymes. To gain more insight into the bacterial enzymes, we cloned the putative ACE from the phytopathogenic bacterium, Xanthomonas axonopodis pv. citri, named XcACE. The 2 kb open reading frame encodes a 672-amino-acid soluble protein containing a single active site. In vitro expression and biochemical characterization revealed that XcACE is a functional 72 kDa dipeptidyl-carboxypeptidase. As in mammals, this metalloprotease hydrolyses angiotensin I into angiotensin II. XcACE is sensitive to ACE inhibitors and chloride ions concentration. Variations in the active site residues, highlighted by structural modelling, can account for the different substrate selectivity and inhibition profile compared to human ACE. XcACE characterization demonstrates that ACE is an ancestral enzyme, provoking questions about its appearance and structure/activity specialisation during the course of evolution.

PMID: 17597310 [PubMed - as supplied by publisher]

New dry edible bean resists bacterial disease
NEWSFOOD.com Primo piano, Italy - Jun 30, 2007
Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops east of the US Continental Divide. ...

New dry edible bean resists bacterial disease
NEWSFOOD.com Primo piano, Italy - Jun 30, 2007
Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops east of the US Continental Divide. ...

New Dry Edible Bean Resists Bacterial Disease
Agricultural Research, MD - Jun 29, 2007
Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops east of the US Continental Divide. ...

New Dry Edible Bean Resists Bacterial Disease
Agricultural Research, MD - Jun 29, 2007
Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops east of the US Continental Divide. ...

New Dry Edible Bean Resists Bacterial Disease
Agricultural Research, MD - Jun 29, 2007
Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops east of the US Continental Divide. ...

New Dry Edible Bean Resists Bacterial Disease
Agricultural Research, MD - Jun 29, 2007
Caused by the pathogen Xanthomonas campestris pv. phaseoli, bacterial blight is an endemic disease affecting bean crops east of the US Continental Divide. ...