A Second Cluster of Genes that Specify Pathogenicity and Host Response in<i>Pseudomonas solanacearum</i>

Huang, Yong; Xu, Peilin

doi:10.1094/mpmi-3-048

Cited by 14 publications

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“…As noted previously by us and other authors (2,5,7,14,24,25,37,39,44,45) (11, 30, 36a). Some hrp genes are expressed in vitro but only under certain conditions (30,47 …”

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confidence: 74%

“…Besides P. syringae pv. phaseolicola, hrp genes and/or gene clusters from several other members of the P. syringae taxon have been described and cloned (5, 13-16, 24, 30, 33, 37-39), as have those from phylogenetically distinct plant pathogens, such as Pseudomonas solanacearum (2,14), Erwinia amylovora (44,45), and some pathovars of Xanthomonas campestris (2,6,42). Homology between hrp genes has been reported among members of the P. syringae taxon (8a, 24) as well as between P. solanacearum and members of the X. campestris group (2).…”

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Genetic and transcriptional organization of the hrp cluster of Pseudomonas syringae pv. phaseolicola

1991

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The hrp cluster of Pseudomonas syringae pv. phaseolicola encodes functions that are essential for pathogenicity on bean plants and for the elicitation of the hypersensitive response on resistant plants. The cluster was saturated with insertions of transposon Tn3-spice that served both as a mutagen and as a sensitive reporter of the expression of the target regions. The mutations covered a 17.5-kb segment in strain NPS3121, in which seven hrp::Tn5 insertions had been previously mapped, and regions outside this segment. The cluster is organized into seven distinct complementation groups (hrpL, hrpAB, hrpC, hrpD, hrpE, hrpF, and hrpSR) on the basis of the analysis of over 100 Tn3-spice insertions in plasmids and 43 similar insertions in the chromosome; it spans nearly 22 kb and is chromosomally located. The transcriptional orientation of all genes in the cluster was established by measuring the level of ice nucleation activity of complemented merodiploids carrying chromosomal hrp::inaZ fusions after inoculation in Red Kidney bean leaves. Although all seven loci were actively expressed in Red Kidney bean leaves, none of them was substantially expressed when the bacteria were grown in King B broth medium. Mutations in all loci, except those in hrpC, greatly reduced the ability of the bacteria to multiply in bean leaves. Mutations in the hrpC locus, although preventing the bacteria from eliciting a hypersensitive reaction on tobacco, allowed the bacteria to produce delayed and attenuated symptoms in Red Kidney bean leaves and to multiply to a level 102. to 103-fold lower than that of the wild-type strain. This is the first comprehensive report of the genetic and transcriptional organization of the hrp gene cluster in a phytopathogenic bacterium.The bean halo blight pathogen, Pseudomonas syringae pv. phaseolicola, possesses a group of genes, designated hrp ("harp"), that are essential for the development of disease symptoms and for the elicitation of the hypersensitive reaction on resistant plants. The majority of known hrp genes in this bacterium are clustered in a large genomic region that has been designated the hrp cluster, whereas one locus (hrpM) is located elsewhere in the genome (24,29,31,36). Besides P. syringae pv. phaseolicola, hrp genes and/or gene clusters from several other members of the P. syringae taxon have been described and cloned (5, 13-16, 24, 30, 33, 37-39), as have those from phylogenetically distinct plant pathogens, such as Pseudomonas solanacearum (2, 14), Erwinia amylovora (44, 45), and some pathovars of Xanthomonas campestris (2,6,42). Homology between hrp genes has been reported among members of the P. syringae taxon (8a, 24) as well as between P. solanacearum and members of the X. campestris group (2).The nature and precise role of most hrp gene products in the plant-bacterium interaction are unknown. Three hrp loci have been analyzed in some detail in P. syringae pv. phaseolicola. A locus designated hrpS encodes a protein that shares sequence similarity to NtrC-like regulatory proteins (...

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“…As noted previously by us and other authors (2,5,7,14,24,25,37,39,44,45) (11, 30, 36a). Some hrp genes are expressed in vitro but only under certain conditions (30,47 …”

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confidence: 74%

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confidence: 99%

Genetic and transcriptional organization of the hrp cluster of Pseudomonas syringae pv. phaseolicola

1991

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“…In Pseudomonas solanacearum, two hrp clusters have been identified (16); interestingly, one of these clusters contained in the cosmid pVir2 was found to hybridize to the DNA of several X. campestris pathovars, including X. campestris pv. campestris (2).…”

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confidence: 99%

A plant-inducible gene of Xanthomonas campestris pv. campestris encodes an exocellular component required for growth in the host and hypersensitivity on nonhosts

Kamoun

Kado

1990

J Bacteriol

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Using Tn4431, a transposon that allows transcriptional fusions to a promoterless luciferase (lux) operon, we have isolated a nonpathogenic mutant of Xanthomonas campestris pv. campestris, i.e., JS111, that does not incite any of the black rot symptoms on all tested cruciferous host plants (J. J. Shaw, L. G. Settles, and C. I. Kado, Mol. Plant Microbe Interact. 1:3945, 1988). In the study reported here, we determined that in contrast to the wild-type strain, JS111 is unable to induce a hypersensitive necrotic response on nonhost plants such as datura, tomato, and cucumber, suggesting that JS111 is a nonpathogenic, nonhypersensitive Hrp mutant. JS111 displayed culture growth rates, exopolysaccharide production, and protease, pectate lysase, cellulase, amylase, and phosphatase activities comparable to those of the wild-type strain. However, the growth of JS111 in host leaves was markedly attenuated. Coinoculation of JS111 with the wild-type strain in cauliflower or radish leaves rescued the growth deficiency of the mutant to normal levels. The locus mutated in JS11 was cloned and named hrpXc, and transcriptional and genetic complementation analyses of the hrpXc locus were conducted. The regulation of hrpXc expression was also investigated in vitro and in planta, using fusions to a lux or chloramphenicol acetyltransferase reporter gene. The hrpXc gene was found to be strongly induced in radish leaves. This is the first report and analysis of a hrp locus from a Xanthomonas species.In recent years, the application of molecular genetic approaches to plant pathogenic bacteria has led to the identification and isolation of a number of genes involved in the interaction between the bacterium and the plant. These genes can be tentatively classified into four groups relative to the phenotype they confer on the bacteria. (i) hrp (hypersensitive response and pathogenicity) genes are required for pathogenicity on hosts and for the induction of a hypersensitive response (HR) on nonhost plants (1, 2, 23). (ii) dsp (disease-specific) genes are necessary for pathogenicity but do not affect HR induction on nonhosts (6). (iii) avr (avirulence) genes confer race-or cultivar-specific interactions. The avirulence genes are dominant genes and restrict the host range of the bacteria to the cultivars that contain a complementary resistance gene(s) (36, 37). (iv) Of considerable importance are the hsv (host-specific virulence) genes that have been isolated from bacteria with wide host ranges and are required for pathogenicity on only some of the host plants (13, 14, 28; D. Gabriel, ASM News 52:19-25, 1986). hsv genes can extend the host range when introduced in narrow-host-range strains (25,39).In this paper, we report the identification and characterization of a hrp gene from Xanthomonas campestris pv. campestris, the causal agent of the black rot of crucifers, a worldwide and economically important plant disease (40). Hydathodes are the principal natural mode of entry in the plant, although secondary entry sites can develop in the roots ...

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“…On the basis of these results, there should be large differences in the epiphytic survival of established populations of bacterial cells and newly inoculated cells that have been grown in laboratory media. Plant signals have been found to induce genes involved in other plant-associated phenotypes, including pathogenicity and induction of a hypersensitive reaction (2,9,22,23,30,44), virulence (24,47), phytotoxin production (39), and nodulation of leguminous plants (13). Interestingly, plant factors have also been found to induce many genes whose functions are not known (10,42); possibly some of these are involved in epiphytic fitness.…”

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Comparison of the Behavior of Epiphytic Fitness Mutants of Pseudomonas syringae under Controlled and Field Conditions

Beattie

Lindow

1994

Appl Environ Microbiol

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The epiphytic fitness of four Tn5 mutants of Pseudomonas syringae that exhibited reduced epiphytic fitness in the laboratory was evaluated under field conditions. The mutants differed more from the parental strain under field conditions than under laboratory conditions in their survival immediately following inoculation onto bean leaves and in the size of the epiphytic populations that they established, demonstrating that their fitness was reduced more under field conditions than in the laboratory. Under both conditions, the four mutants exhibited distinctive behaviors. One mutant exhibited particularly large population decreases and short half-lives following inoculation but grew epiphytically at near-wild-type rates, while the others exhibited reduced survival only in the warmest, driest conditions tested and grew epiphytically at reduced rates or, in the case of one mutant, not at all. The presence of the parental strain, B728a, did not influence the survival or growth of three of the mutants under field conditions; however, one mutant, an auxotroph, established larger populations in the presence of B728a than in its absence, possibly because of cross-feeding by B728a in planta. Experiments with B728a demonstrated that established epiphytic populations survived exposure of leaves to dry conditions better than newly inoculated cells did and that epiphytic survival was not dependent on the cell density in the inoculum. Three of the mutants behaved similarly to two nonpathogenic strains of P. syringae, suggesting that the mutants may be altered in traits that are missing or poorly expressed in naturally occurring nonpathogenic epiphytes.

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A Second Cluster of Genes that Specify Pathogenicity and Host Response inPseudomonas solanacearum

Cited by 14 publications

References 0 publications

Genetic and transcriptional organization of the hrp cluster of Pseudomonas syringae pv. phaseolicola

Genetic and transcriptional organization of the hrp cluster of Pseudomonas syringae pv. phaseolicola

A plant-inducible gene of Xanthomonas campestris pv. campestris encodes an exocellular component required for growth in the host and hypersensitivity on nonhosts

Comparison of the Behavior of Epiphytic Fitness Mutants of Pseudomonas syringae under Controlled and Field Conditions

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