A Repetitive DNA Sequence DifferentiatesXanthomonas campestrispv.oryzaefrom Other Pathovars ofX. campestris

Leach, Jan E.; White, Frank F.; Rhoads, M L; Leung, Hei

doi:10.1094/mpmi-3-238

Cited by 100 publications

(82 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Four different IS elements (IS1112, IS1113, TNX6, and TNX7) have been previously reported for X. oryzae pv. oryzae (20,27). All four elements are present in multiple copies within the X. oryzae pv.…”

Section: Discussionmentioning

confidence: 99%

Stationary-Phase Variation Due to Transposition of Novel Insertion Elements in Xanthomonas oryzae pv. oryzae

Rajeshwari

Sonti

2000

J Bacteriol

View full text Add to dashboard Cite

Xanthomonas oryzae pv. oryzae causes bacterial leaf blight, a serious disease of rice. Spontaneous mutants which are deficient for virulence and extracellular polysaccharide (Eps) production accumulate in large numbers in stationary-phase cultures of this bacterium, a phenomenon which we have called stationary-phase variation. A clone (pSD1) carrying the Eps biosynthetic gene (gum) cluster of X. oryzae pv. oryzae restored Eps production and virulence to several spv (for stationary-phase variation) mutants. Data from localized recombination analysis, Southern hybridization, PCR amplification, and sequence analysis showed that the mutations are due to insertion of either one of two novel endogenous insertion sequence (IS) elements, namely, ISXo1 and ISXo2, into gumM, the last gene of the gum gene cluster. The results of Southern analysis indicate the presence of multiple copies of both IS elements in the genome of X. oryzae pv. oryzae. These results demonstrate the role of IS elements in stationary-phase variation in X. oryzae pv. oryzae.In their natural environment, bacteria often encounter nutritionally limited conditions which resemble the stationaryphase conditions of laboratory cultures. Gram-positive bacteria respond to the adverse conditions by forming resistant spores. Gram-negative bacteria exhibit reduced growth, and several genes that confer resistance to stress during starvation are transcriptionally induced in the stationary phase. Much of the transcriptional regulation in the stationary phase is mediated by rpoS, a gene that encodes the stationary-phase sigma factor ( S ) of RNA polymerase (14, 21). Several Escherichia coli mutants that have a competitive advantage in stationaryphase cultures have been shown to carry mutations in the rpoS gene (38).Spontaneous and reversible phenotypic variations mediated by various DNA rearrangements, such as insertions, DNA duplications, inversions, deletions, and frameshift mutations, are strategies adopted by bacteria to cope with adverse environmental conditions (7). A few examples are intragenic duplications in a regulatory gene in the mushroom pathogen Pseudomonas tolaasii (11), large chromosomal duplications that promote growth during carbon starvation in Salmonella enterica serovar Typhimurium (34), insertions in Shigella flexneri (24), frameshift mutations in Bordetella pertussis (35), and flagellar-phase variation mediated by DNA inversion in serovar Typhimurium (39). In the well-studied plant-pathogenic bacterium Ralstonia solanacearum, phenotypic changes were shown to be due to either mutations in the phcA regulatory gene (2), overproduction of a negative regulatory element (16), or excision of an episome from the bacterial chromosome (26).Xanthomonas oryzae pv. oryzae causes bacterial leaf blight, a serious disease of rice. Like other xanthomonads, this bacterium produces copious amounts of an extracellular polysaccharide (Eps). The Eps produced by a related bacterium, Xanthomonas campestris pv. campestris, is the industrially important xanthan gum, whi...

show abstract

Section: Discussionmentioning

confidence: 99%

Stationary-Phase Variation Due to Transposition of Novel Insertion Elements in Xanthomonas oryzae pv. oryzae

Rajeshwari

Sonti

2000

J Bacteriol

View full text Add to dashboard Cite

show abstract

“…Genomic DNA was isolated from the X. oryzae pv. oryzae strains as described earlier (23). Plasmids were isolated from E. coli cultures by using the alkaline lysis method (5).…”

Section: Methodsmentioning

confidence: 99%

Genetic Locus Encoding Functions Involved in Biosynthesis and Outer Membrane Localization of Xanthomonadin in Xanthomonas oryzae pv. oryzae

et al. 2002

View full text Add to dashboard Cite

Xanthomonadins are membrane-bound, brominated, aryl-polyene pigments specific to the genus Xanthomonas. We have characterized a genetic locus (pig) from Xanthomonas oryzae pv. oryzae which contains four open reading frames (ORFs) that are essential for xanthomonadin production. Three of these ORFs are homologous to acyl carrier proteins, dehydratases, and acyl transferases, suggesting a type II polyketide synthase pathway for xanthomonadin biosynthesis. The fourth ORF has no homologue in the database. For the first time, we report that a putative cytoplasmic membrane protein encoded in the pig locus is required for outer membrane localization of xanthomonadin in X. oryzae pv. oryzae. We also report the identification of a novel 145-bp palindromic Xanthomonas repetitive intergenic consensus element that is present in two places in the pig locus. We estimate that more than 100 copies of this element might be present in the genome of X. oryzae pv. oryzae and other xanthomonads.Members of the genus Xanthomonas cause diseases in a wide range of host plants (25). Many of them can also survive and multiply on plant leaf surfaces as epiphytes without affecting the host (15,44). A characteristic feature of most xanthomonads is the production of yellow, membrane-bound (46), halogenated, aryl-polyene pigments (2, 3) called xanthomonadins, which serve as useful chemotaxonomic (45) and diagnostic markers (41). Xanthomonadin is not essential for in planta growth of bacterial cells (13,35,48). However, it is being established progressively that xanthomonadin protects bacteria against photooxidative damage. Pigment-deficient mutants of Xanthomonas juglandis (20), Xanthomonas oryzae pv. oryzae (37), and Xanthomonas campestris pv. campestris (33) are more susceptible to photooxidative damage than are wild-type strains. In vitro, xanthomonadin protects membrane lipids in egg-phosphatidylcholine liposomes against peroxidation (37). A transposon-induced xanthomonadin-deficient mutant of X. campestris pv. campestris has been recently shown to be 1,000-fold reduced for epiphytic survival in conditions of high light intensity (33). These observations suggest that xanthomonadin might aid the survival of xanthomonads on plant leaf surfaces by providing protection against photooxidative damage. In spite of their apparent importance, very little is known about the biosynthesis and mechanism of action of xanthomonadins.An 18.6-kb genomic region from X. campestris pv. campestris that contains seven transcriptional units (pig genes) required for xanthomonadin production has been isolated (34, 35). One of the transcriptional units, pigB, is involved in biosynthesis of a diffusible factor that affects the production of xanthomonadin as well as extracellular polysaccharide (34). The unavailability of nucleotide sequences for these transcriptional units, however, limits further insight into the mechanism of xanthomonadin biosynthesis. X. oryzae pv. oryzae mutants that are defective in shikimate dehydrogenase activity have been shown to be deficie...

show abstract

“…RFLP analysis has been used to differentiate plantpathogenic bacteria at the pathovar level (Lazo & Gabriel, 1987;Denny et al, 1988;Leach et al, 1990;Qhobela et al, 1990) as well as to assess relatedness among bacterial strains (Gabriel et al, 1988;Cook et al, 1989Cook et al, , 1991Hartung & Civerolo, 1989;Leach et al, 1992;Pruvost et al, 1992;Qhobela et al, 1991 ;Qhobela & Claflin, 1992;Xu & Gonzales, 1991). The conserved nature of rRNA genes allowed the use of a 16+23S rRNA probe from Escherichia coli for the identification of bacteria and for taxonomic studies (Grimont et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

Assessment of genetic diversity among strains of Xanthomonas campestris pv. manihotis

Verdier¹,

Dongo²,

Boher

1993

Journal of General Microbiology

View full text Add to dashboard Cite

campestris ~ ~~Three-hundred and twenty-six strains of Xanthomonas campestris pv. manihotis from 22 countries were studied to detect and assess genetic and evolutionary relationships within the pathovar. A range of techniques was used for this study including restriction fragment length polymorphism (RFLP) analysis. The probes used for the RFLP analysis were 16 + 23s rRNA genes from Escherichia coli and three restriction fragments from the chromosomal and plasmid DNA of X. campestris pv. manihotis. Analysis of the rRNA probe data showed five RFLP groups whilst the other three probes were used to further sub-divide these groupings. Genetic variability of X. campestris pv. manihotis was pronounced in strains from South America where the host plant originated but was limited in strains from other regions. The results obtained confirm the hypothesis that the pathogen has been introduced only recently to Africa and suggests that African strains have not as yet diversified significantly at the chromosomal level. Our results indicate that rRNA and DNA probes are useful tools for epidemiological studies and in following the genetic evolution of strains.

show abstract

A Repetitive DNA Sequence DifferentiatesXanthomonas campestrispv.oryzaefrom Other Pathovars ofX. campestris

Cited by 100 publications

References 0 publications

Stationary-Phase Variation Due to Transposition of Novel Insertion Elements in Xanthomonas oryzae pv. oryzae

Stationary-Phase Variation Due to Transposition of Novel Insertion Elements in Xanthomonas oryzae pv. oryzae

Genetic Locus Encoding Functions Involved in Biosynthesis and Outer Membrane Localization of Xanthomonadin in Xanthomonas oryzae pv. oryzae

Assessment of genetic diversity among strains of Xanthomonas campestris pv. manihotis

Contact Info

Product

Resources

About