Strategies in pathogenesis: mechanistic specificity in the detection of generic signals

Duban, Matthieu; Lee, Kyung‐Hee; Lynn, David G.

doi:10.1111/j.1365-2958.1993.tb01155.x

Cited by 29 publications

(20 citation statements)

References 75 publications

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“…Previously, several groups noted that one or two methoxy groups in the ortho position are required, and a wide variety of substituents are permitted in the position para to the hydroxyl group of the phenol (29,38). However, the vir genes of strain KU12 are induced by several compounds, including 4-hydroxyacetophenone, p-coumaric acid, and phenol, that lack any methoxy groups.…”

Section: Discussionmentioning

confidence: 99%

Genetic evidence for direct sensing of phenolic compounds by the VirA protein of Agrobacterium tumefaciens.

Lee

Jin²,

Sim³

et al. 1995

Proc. Natl. Acad. Sci. U.S.A.

114

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The virulence (vir) genes of Agrobacterium tumefaciens are induced by low-molecular-weight phenolic compounds and monosaccharides through a two-component regulatory system consisting of the VirA and VirG proteins. However, it is not clear how the phenolic compounds are sensed by the VirA/VirG system. We tested the vir-inducing abilities of 15 different phenolic compounds using four wildtype strains ofA. tumefaciens-KU12, C58, A6, and Bo542. We analyzed the relationship between structures of the phenolic compounds and levels of vir gene expression in these strains. In strain KU12, vir genes were not induced by phenolic compounds containing 4'-hydroxy, 3'-methoxy, and 5'-methoxy groups, such as acetosyringone, which strongly induced vir genes of the other three strains. On the other hand, vir genes of strain KU12 were induced by phenolic compounds containing only a 4'-hydroxy group, such as 4-hydroxyacetophenone, which did not induce vir genes of the other three strains. The vir genes of strains KU12, A6, and Bo542 were all induced by phenolic compounds containing 4'-hydroxy and 3'-methoxy groups, such as acetovanillone. By transferring different Ti plasmids into isogenic chromosomal backgrounds, we showed that the phenolic-sensing determinant is associated with Ti plasmid. Subcloning Table 2 show that the induction response to different phenolic compounds varies among the different strains.Under our standard induction conditions, vir genes in both the octopine-type strain A6 and the succinamopine-type strain Bo542 were strongly induced by all phenolic compounds in group A. The nopaline-type strain C58 showed a moderate level of vir gene induction by acetosyringone and sinapinic acid. However, no response to syringaldehyde, syringic acid, and 2,6-dimethoxyphenol was observed. Surprisingly, we found that all phenolic compounds in group A, including acetosyringone, the most commonly used vir gene inducer in the laboratory, were unable to induce the vir genes of strain KU12. All strains except C58 responded to acetovanillone and ferulic acid of group B, and strains KU12 and Bo542 were both induced by guaiacol. However, only strain Bo542 was induced by vanillin of group B. In our hands, strain A6 was not induced by vanillin, a phenolic compound classified as a strong vir gene inducer by Melchers et al. (29) using A. tumefaciens strain LBA2516, which contains an octopine-type Ti plasmid, pTiB6, that is closely related to pTiA6 (12). The reason for this discrepancy is not clear. Of special interest is the observation that the vir genes of strain KU12 were highly induced by a group of compounds in group C that lack both methoxy groups. These compounds included 4-hydroxyacetophenone, p-coumaric acid, and phenol, which had previously been reported to be non-vir gene inducers (29). In support of this latter report, the three otherA. tumefaciens strains were indeed not induced by the phenolic compounds in group C.We tested vir gene induction by other phenolic compounds that lacked the hydroxyl group at the R4 posi...

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Section: Discussionmentioning

confidence: 99%

Genetic evidence for direct sensing of phenolic compounds by the VirA protein of Agrobacterium tumefaciens.

Lee

Jin²,

Sim³

et al. 1995

Proc. Natl. Acad. Sci. U.S.A.

114

View full text Add to dashboard Cite

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“…The types of phenolic compounds reported to have signal activity include certain acetophenones (e.g. acetosyringone), monolignols, chalcones, and flavonoids (Spencer and Towers, 1988;Zerback et al, 1989;Duban et al, 1993). In the rhizobia, specific plant flavonoids were discovered to activate nodulation (nod) genes essential for establishment of symbiosis (Peters et al, 1986).…”

mentioning

confidence: 99%

Analysis of Sweet cherry (Prunus avium L.) Leaves for Plant Signal Molecules That Activate the syrB Gene Required for Synthesis of the Phytotoxin, Syringomycin, by Pseudomonas syringae pv syringae

Geibel

Bonsall

et al. 1995

Plant Physiol.

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An important aspect of the interaction of Pseudomonas syringae pv syringae with plant hosts is the perception of plant signal molecules that regulate expression of genes, such as syrll, required for synthesis of the phytotoxin, syringomycin. I n this study, the leaves of sweet cherry (Prunus avium 1.) were analyzed to determine the nature of the syrB-inducing activity associated with tissues of a susceptible host. Crude leaf extracts yielded high amounts of total signal activity of more than 12,000 units g-' (fresh weight) based on activation of a syr6-lacZ fusion in strain B3AR132. l h e signal activity was fractionated by C,, reversed-phase high-performance liquid chromatography and found to be composed of phenolic glycosides, which were resolved i n three regions of the high-performance liquid chromatography profile, and sugars, which eluted with the void volume. Two flavonol glycosides, quercetin 3-rutinosyl-4'-glucoside and kaempferol 3-rutinosyl-4'-glucoside, and a flavanone glucoside, dihydrowogonin 7-glucoside, were identified. l h e flavonoid glycosides displayed similar specific signal activities and were comparable in signal activity to arbutin, a phenyl p-glucoside, giving rise to between 120 and 160 units of /3-galactosidase activity at 10 p~. Although o-fructose exhibits intrinsic low leve1 syrll-inducing signal activity, o-fructose enhanced by about 10-fold the signal activities of the flavonoid glycosides at low concentrations (e.g. 10 PM). This demonstrates that flavonoid glycosides, which represent a new class of phenolic plant signals sensed by P. s. syringae, are i n sufficient quantities in the leaves of P. avium to activate phytotoxin synthesis.Bacteria commonly detect in the plant environment specific phenolic compounds that serve as signals in regulating expression of genes critica1 to phytopathogenesis (Peters and Verma, 1990). This was first observed for Agrobacterium tumefaciens, which senses in wounded tissues

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“…Table 5 presents the molecular orbital coefficients for each of these pn orbital in basis set I, while Table 6 gives the bare ( l , l~l / r~, 2~1 , 1 ) integral for each Z choice. Notice that the Z = 5.8 orbital yields the smallest (1,l ~l / r~, 2~1 , 1 ) integral because this orbital is the most diffuse spatially. The rather small variation of Z, however, induces changes in the "theoretical" one-center, two-electron integrals which range over 3 eV.…”

Section: Exploratory 97" Calculations For Hexatrienementioning

confidence: 97%

“…This is a common trend in Z" calculations with Rydberg-extended valence spaces.' 1,12,26,28 Unfortunately, the Rydberg-extended valence space barely affects the excitation energy of the l'B, state. As a result, the low-lying singlet 1 'B, states in polyenes may be very difficult to describe using a purely ab initio derived semiempirical method because the ab initio constrained P calculations simply cannot account for all of the correlation in these states with the present third-order treatment.…”

Section: B Constrained Large Basis Set 9p Calculationsmentioning

confidence: 99%

Ab Initio Computation of Semiempirical .pi.-Electron Methods. 4. True and Approximate Effective Hamiltonians for Hexatriene and Related Conjugated Polyenes

Martin¹,

Freed²

1995

J. Phys. Chem.

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The multireference configuration ab initio effective valence shell Hamiltonian ( X Y ) method is used to compute the true n-electron effective Hamiltonian of hexatriene, to provide new theoretical predictions of excited states and to further our understanding of semiempirical n-electron theory. The XY approach generates highly accurate vertical excitation energies for the low-lying valencelike states with a single large-scale calculations using the same valence orbitals for every excited state. We present a fairly automated procedure for choosing P valence orbitals and determine a single XY six valence orbital valence space that reproduces experimental vertical excitation energies to within 0.26, 0.01, 0.08, 0.04, and 0.03 eV for the llB,, l'Ag, 2'B,, 13B,, and 13A, valencelike excited states. The calculations also provide the first predictions for the 23B, and 23Ag state vertical excitation energies (5.22 and 6.69 eV, respectively). These results compare extremely well with complete active space second-order perturbation theory calculations (CASPT2) which employ larger active spaces. A second valence space (constructed for comparisons with semiempirical n-electron theory) treats most low-lying excited states well but also reproduces the 12A, state ionization potential to with 0.08 eV.This allows us to predict for the first time the second n-electron ionization potential to lie at 10.34 eV. Given our highly accurate ab initio model, we then apply a series of systematic approximations which reduce the a b initio n-electron P to a purely a b initio PPP Hamiltonian (denoted as P -P P P ) . The new 9 -P P P out performs the traditional semiempirical PPP parametrization. The a b initio P -P P P parameters compare well with the standard semiempirical values and display remarkable transferability between ethylene, transbutadiene, and hexatriene. Many a b initio parameters, which are neglected in the semiempirical PPP model, are actually quite small, but only when including correlation contributions. On the other hand, contributions from many nonnegligible a b initio one-, two-, and three-electron parameters must still be retained in order to improve the accuracy of the ab initio PPP model. We present an improved, generalized PPP model that includes all dominant many-body interactions (greater than 0.1 eV).

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Strategies in pathogenesis: mechanistic specificity in the detection of generic signals

Cited by 29 publications

References 75 publications

Genetic evidence for direct sensing of phenolic compounds by the VirA protein of Agrobacterium tumefaciens.

Genetic evidence for direct sensing of phenolic compounds by the VirA protein of Agrobacterium tumefaciens.

Analysis of Sweet cherry (Prunus avium L.) Leaves for Plant Signal Molecules That Activate the syrB Gene Required for Synthesis of the Phytotoxin, Syringomycin, by Pseudomonas syringae pv syringae

Ab Initio Computation of Semiempirical .pi.-Electron Methods. 4. True and Approximate Effective Hamiltonians for Hexatriene and Related Conjugated Polyenes

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