Identification of a Family of Avirulence Genes from<i>Xanthomonas oryzae</i>pv.<i>oryzae</i>

Hopkins, Chris; White, Frank F.; Choi, Seong Ho; Guo, Ailan; Leach, Jan E.

doi:10.1094/mpmi-5-451

Cited by 247 publications

(132 citation statements)

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“…malvacearum (5,8); and avrXa10 and avrXa7 of Xanthomonas oryzae pv. oryzae (14). Among these, only avrb6 and pthA are known to have pleiotropic pathogenicity functions (5,30,35).…”

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confidence: 99%

Intragenic recombination of a single plant pathogen gene provides a mechanism for the evolution of new host specificities

Yang

Gabriel

1995

J Bacteriol

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Gene pthA is required for virulence of Xanthomonas citri on citrus plants and has pleiotropic pathogenicity and avirulence functions when transferred to many different xanthomonads. DNA sequencing revealed that pthA belongs to a family of Xanthomonas avirulence/pathogenicity genes characterized by nearly identical 102-bp tandem repeats in the central region. By inserting an nptI-sac cartridge into the tandemly repeated region of pthA as a selective marker, intragenic recombination among homologous repeats was observed in both Xanthomonas spp. and Escherichia coli. Intragenic recombination within pthA created new genes with novel host specificities and altered pathogenicity and/or avirulence phenotypes. Many pthA recombinants gained or lost avirulence function in pathogenicity assays on bean, citrus, and cotton cultivars. Although the ability to induce cell division (hyperplastic cankers) on citrus could be lost, this ability was not acquired on cotton or bean plants. Intragenic recombination therefore provides a genetic mechanism for the generation of multiple, different, and gratuitous avirulence genes from a single, required, host-specific pathogenicity gene.In gene-for-gene interactions between plants and microbial plant pathogens, host plant resistance results from the genetic recognition of resistance (R) genes in the plant and avirulence (avr) genes in the pathogen (10,17). It is unknown why microbial plant pathogens carry genes that function to limit virulence, since the majority of these genes are apparently dispensable (11). Numerous studies of pathogen avr genes have revealed spontaneous loss-of-function mutations (15,20). Not surprisingly, these mutations can involve gene deletion (8) or transposon insertion (16). Mutational analyses also reveal spontaneous gain-of-function mutations that generate new avirulence specificities and new pathogen races at approximately the same frequency as loss-of-function mutations (28). Although presumably an avr gene may be reactivated by reverse mutation, there are no reports of natural mechanisms whereby new avirulence specificities, pathogen races, or avr genes are generated.Xanthomonas citri is the causal agent of citrus canker disease, which occurs worldwide and is subject to eradication and quarantine regulations in many countries. A pathogenicity gene, pthA, is essential for the pathogen to cause hyperplastic canker symptoms on citrus (29). Furthermore, when transferred to other xanthomonads, pthA confers the ability to induce hyperplastic cankers on citrus and a hypersensitive response (HR) on other hosts (30). Therefore, pthA exhibits pleiotropic pathogenicity and avirulence functions. Southern hybridization, restriction analysis, and partial DNA sequencing have shown that pthA belongs to a major avr gene family widespread in the genus Xanthomonas (30). Members of this gene family include avrBs3 and avrBs3-2 of Xanthomonas campestris pv. vesicatoria (2, 3); avrB4, avrb6, avrb7, avrBIn, avrB101, and avrB102 of X. campestris pv. malvacearum (5, 8); and avrXa10 ...

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“…malvacearum (5,8); and avrXa10 and avrXa7 of Xanthomonas oryzae pv. oryzae (14). Among these, only avrb6 and pthA are known to have pleiotropic pathogenicity functions (5,30,35).…”

mentioning

confidence: 99%

Intragenic recombination of a single plant pathogen gene provides a mechanism for the evolution of new host specificities

Yang

Gabriel

1995

J Bacteriol

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“…Also, the repetitive elements IS1113 and IS1112 hybridized with large number of bands and served as informative probes (Nelson et al, 1994). One of the avirulence genes, avrXa10, has also been used as a probe to differentiate Xoo strains from the Philippines (Kelemu and Leach, 1990;Hopkins et al, 1992). The probe hybridized with 9 to 23 different sized DNA fragments in the genome of a strain.…”

Section: Races and Strains Of Xoomentioning

confidence: 99%

Review on Bacterial Blight of rice caused by Xanthomonas oryzae pv. oryzae: different management approaches and role of Pseudomonas fluorescens as a potential biocontrol agent

Bora¹,

Baruah²,

Talukdar³

et al. 2017

Int.J.Curr.Microbiol.App.Sci

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“…2). Two additional, as yet uncharacterized, R genes of rice have similar requirements for the transcription activation domain and nuclear localization signal motifs of the corresponding transcription activation-like (TAL) effectors as required for AvrXa27-mediated induction of Xa27 (Hopkins et al, 1992;Zhu et al, 1998;Yang et al, 2000). Cloning and analysis of these R genes will reveal whether the effectors and R gene expression have similar features to Xa27 (Porter et al, 2003;Chen et al, 2008;Gu et al, 2008).…”

Section: Resistance and Susceptibility Genes To Xoomentioning

confidence: 99%