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J E Leach

Publications and source records attributed to J E Leach.

27 records · Page 2Linked to original sources
PubMed1995

Genetic Diversity of Xanthomonas oryzae pv. oryzae in Asia.

Restriction fragment length polymorphism and virulence analyses were used to evaluate the population structure of Xanthomonas oryzae pv. oryzae, the rice bacterial blight pathogen, from several rice-growing countries in Asia. Two DNA sequences from X. oryzae pv. oryzae, IS1112, an insertion sequence, and avrXa10, a member of a family of avirulence genes, were used as probes to analyze the genomes of 308 strains of X. oryzae pv. oryzae collected from China, India, Indonesia, Korea, Malaysia, Nepal, and the Philippines. On the basis of the consensus of three clustering statistics, the collection formed five clusters. Genetic distances within the five clusters ranged from 0.16 to 0.51, and distances between clusters ranged from 0.48 to 0.64. Three of the five clusters consisted of strains from a single country. Strains within two clusters, however, were found in more than one country, suggesting patterns of movement of the pathogen. The pathotype of X. oryzae pv. oryzae was determined for 226 strains by inoculating five rice differential cultivars. More than one pathotype was associated with each cluster; however, some pathotypes were associated with only one cluster. Most strains from South Asia (Nepal and India) were virulent to cultivars containing the bacterial blight resistance gene xa-5, while most strains from other countries were avirulent to xa-5. The regional differentiation of clusters of X. oryzae pv. oryzae in Asia and the association of some pathotypes of X. oryzae pv. oryzae with single clusters suggested that strategies that target regional resistance breeding and gene deployment are feasible.

Journal Article↗
PubMed1994

Identification of the XorII methyltransferase gene and a vsr homolog from Xanthomonas oryzae pv. oryzae.

The gene encoding the XorII methyltransferase (M.XorII) was cloned from Xanthomonas oryzae pv. oryzae and characterized in Escherichia coli. The M.XorII activity was localized to a 3.1 kb BamHI-BstXI fragment, which contained two open reading frames (ORFs) of 1272 nucleotides (424 amino acids) and 408 nucleotides (136 amino acids). Ten polypeptide domains conserved in other M5 cytosine methyltransferases (MTases) were identified in the deduced amino acid sequence of the 1272 ORF. E. coli Mrr+ strains were transformed poorly by plasmids containing the XorII MTase gene, indicating the presence of at least one MCG in the recognition sequence for M.XorII (CGATCG). The 408 nucleotide ORF was 36% identical at the amino acid level to sequences of the E. coli dem-vsr gene, which is required for very short patch repair. X. oryzae pv. oryzae genomic DNA that is resistant to digestion by PvuI and XorII hybridizes with a 7.0 kb fragment containing the XorII MTase gene and vsr homolog, whereas DNA from strains that lack M.XorII activity do not hybridize with the fragment.

Amino Acid Sequence↗
PubMed1994

Relationship between Phylogeny and Pathotype for the Bacterial Blight Pathogen of Rice.

Several transposable elements were isolated from the genome of Xanthomonas oryzae pv. oryzae. These elements and an avirulence gene isolated from X. oryzae pv. oryzae were used as hybridization probes for a collection of X. oryzae pv. oryzae strains from the Philippines. Each of the sequences was present in multiple copies in all strains examined and showed distinct patterns of hybridizing bands. Phenograms were derived from the restriction fragment length polymorphism data obtained for each of the individual probes and for pooled data from multiple probes. The phenograms derived from the different probes differed in topology and, on the basis of bootstrap analysis, were not equally robust. For all of the probes, including the avirulence gene, some groups (even some haplotypes) consisted of multiple races. The strains were grouped into four major clusters on the basis of the two probes giving the highest bootstrap values. These groups were inferred to represent phylogenetic lineages. Three of the six races of X. oryzae pv. oryzae appeared in more than one of the lineages, and another was present in two sublineages. For three of the races, strains representing different phenetic groups were inoculated on rice cultivars carrying 10 resistance genes. Two new races were differentiated, corresponding to pathogen lineages identified by DNA typing. On the basis of DNA and pathotypic analyses, together with information on the spatial and temporal distribution of the pathogen types from this and other studies, a general picture of X. oryzae pv. oryzae evolution in the Philippines is presented.

Journal Article↗
PubMed1992

Increased Activity of a Cationic Peroxidase Associated with an Incompatible Interaction Between Xanthomonas oryzae pv oryzae and Rice (Oryza sativa).

Rice (Oryza sativa L.) cultivar Cas 209 carries the gene Xa-10 for resistance to race 2 of Xanthomonas oryzae pv oryzae, the bacterial blight pathogen. When seedling leaves of Cas 209 plants were infiltrated with bacterial cell suspensions of strain PXO86(Rif) (race 2, incompatible), total peroxidase activity in extracts from extracellular spaces increased almost threefold between 16 and 24 hours after inoculation. The increase in total peroxidase activity in extracellular extracts was correlated with the appearance of a 43-kilodalton peroxidase isoenzyme with an isoelectric point of 8.6. Increases in the activities of two anionic peroxidase isoenzymes also were associated with the incompatible interaction. Later during the interactions, total peroxidase activities increased in both compatible (cv Cas 209 infiltrated with race 1, PXO61(Sm)) and control (Cas 209 infiltrated with water) treatments, but final activity levels were less than that observed in the incompatible combination. Similarly, the cationic peroxidase was detected in all three treatments by 48 hours after infiltration, but at reduced levels in compatible and water-infiltrated control treatments relative to the incompatible combination. Accumulation of this peroxidase in extracellular spaces thus may play a role in the defense response in cultivar Cas 209.

Journal Article↗
PubMed1992

Assessment of genetic diversity and population structure of Xanthomonas oryzae pv. oryzae with a repetitive DNA element.

A repetitive DNA element cloned from Xanthomonas oryzae pv. oryzae was used to assess the population structure and genetic diversity of 98 strains of X. oryzae pv. oryzae collected between 1972 and 1988 from the Philippine Islands. Genomic DNA from X. oryzae pv. oryzae was digested with EcoRI and analyzed for restriction fragment length polymorphisms (RFLPs) with repetitive DNA element as a probe. Twenty-seven RFLP types were identified; there was no overlap of RFLP types among the six races from the Philippines. Most variability (20 RFLP types) was found in strains of races 1, 2, and 3, which were isolated from tropical lowland areas. Four RFLP types (all race 5) were found among strains isolated from cultivars grown in the temperate highlands. The genetic diversity of the total population of X. oryzae pv. oryzae was 0.93, of which 42% was due to genetic differentiation between races. The genetic diversities of strains collected in 1972 to 1976, 1977 to 1981, and 1982 to 1986, were 0.89, 0.90, and 0.92, respectively, suggesting a consistently high level of variability in the pathogen population over the past 15 years. Cluster analysis based on RFLP banding patterns showed five groupings at 85% similarity. The majority of strains from a given race were contained within one cluster, except for race 3 strains, which were distributed in three of the five clusters.

DNA, Bacterial↗
PubMed1982

Hydroxyproline-rich bacterial agglutinin from potato : extraction, purification, and characterization.

A protein, extracted from Katahdin potato (Solanum tuberosum L. cv ;Katahdin') tubers and purified by ion exchange chromatography and gel filtration, agglutinates avirulent strains of the bacterial wilt pathogen, Pseudomonas solanacearum, but only weakly agglutinates virulent strains. The agglutinin has very low hemagglutinating activity (in contrast to potato lectin) and is a glycoprotein containing about 61% carbohydrate. The carbohydrate moiety contains 91% (weight%) arabinose, 5% galactose, 3% glucose, and 1% glucosamine. The protein portion is rich in hydroxyproline (42%), lysine (16%), serine (9%), and proline (9%). The entire agglutinin has a molecular weight of 91,000 +/- 5,000 and is very basic (pI > 11). Shape estimations based on the concentration dependence of the sedimentation coefficient, the high viscosity ([eta] = 92.7), the frictional coefficient (f/f(o) = 2.15), and axial ratio (a/b = 25) indicate that the agglutinin is a prolate ellipsoid.

Journal Article↗
PubMedDate not supplied

Identification of a family of avirulence genes from Xanthomonas oryzae pv. oryzae.

Races of Xanthomonas oryzae pv. oryzae, the causal agent of bacterial blight of rice, interact with cultivars of rice in a gene-for-gene specific manner. Multiple DNA fragments of various sizes from all strains of X. o. pv. oryzae hybridized with avrBs3, an avirulence gene from Xanthomonas campestris pv. vesicatoria, in Southern blots; this suggests the presence of several homologs and possibly a gene family. A genomic library of a race 2 strain of X. o. pv. oryzae, which is avirulent on rice cultivars carrying resistance genes xa-5, Xa-7, and Xa-10, was constructed. Six library clones, which hybridized to avrBs3, altered the interaction phenotype with rice cultivars carrying either xa-5, Xa-7, or Xa-10 when present in a virulent race 6 strain. Two avirulence genes, avrXa7 and avrXa10, which correspond to resistance genes Xa-7 and Xa-10, respectively, were identified and partially characterized from the hybridizing clones. On the basis of transposon insertion mutagenesis, sequence homology, restriction mapping, and the presence of a repeated sequence, both genes are homologs of avirulence genes from dicot xanthomonad pathogens. Two BamHI fragments that are homologous to avrBs3 and correspond to avrXa7 and avrXa10 contain a different number of copies of a 102-bp direct repeat. The DNA sequence of avrXa10 is nearly identical to avrBs3. We suggest that avrXa7 and avrXa10 are members of an avirulence gene family from xanthomonads that control the elicitation of resistance in mono- and dicotyledonous plants.

Amino Acid Sequence↗
PubMedDate not supplied

AVRXa10 protein is in the cytoplasm of Xanthomonas oryzae pv. oryzae.

AVRXa10 from Xanthomonas oryzae pv. oryzae was tagged with a unique hydrophilic octapeptide (FLAG) to permit antibody-mediated identification and purification of the gene product. X. o. pv. oryzae that produced tagged AVRXa10 elicited a hypersensitive response (HR) on rice cultivars containing the resistance gene Xa-10, but not on cultivars lacking Xa-10. The tagged AVRXa10 protein purified from Escherichia coli or X. o. pv. oryzae did not elicit a hypersensitive response in rice with the Xa-10 resistance gene. Anti-FLAG monoclonal antibodies reacted with a 119-kDa protein in both E. coli and X. o. pv. oryzae cells expressing the tagged avrXa10 gene. Polyclonal antibodies raised against purified AVRXa10 protein reacted with the 119-kDa protein and several additional proteins from X. o. pv. oryzae, which probably are the products of genes related to avrXa10. Biochemical fractionation and immunoelectronmicroscopy analysis was used to demonstrate that AVRXa10 was located in the cytoplasm of X. o. pv. oryzae cells when grown in planta or in culture medium.

Bacterial Proteins↗