The disease-resistance gene Pto and the fenthion-sensitivity gene fen encode closely related functional protein kinases.

Loh, Ying-Tsu; Martin, Gregory B.

doi:10.1073/pnas.92.10.4181

Cited by 53 publications

(21 citation statements)

References 33 publications

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“…These findings differ from earlier papers that described Pto and Fen as active kinases, with similar activities in vitro [34]–[37]. There are several differences in the protocols used in each case that might explain these discrepancies.…”

Section: Resultscontrasting

confidence: 99%

Pto Kinase Binds Two Domains of AvrPtoB and Its Proximity to the Effector E3 Ligase Determines if It Evades Degradation and Activates Plant Immunity

2014

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The tomato—Pseudomonas syringae pv. tomato (Pst)—pathosystem is one of the best understood models for plant-pathogen interactions. Certain wild relatives of tomato express two closely related members of the same kinase family, Pto and Fen, which recognize the Pst virulence protein AvrPtoB and activate effector-triggered immunity (ETI). AvrPtoB, however, contains an E3 ubiquitin ligase domain in its carboxyl terminus which causes degradation of Fen and undermines its ability to activate ETI. In contrast, Pto evades AvrPtoB-mediated degradation and triggers ETI in response to the effector. It has been reported recently that Pto has higher kinase activity than Fen and that this difference allows Pto to inactivate the E3 ligase through phosphorylation of threonine-450 (T450) in AvrPtoB. Here we show that, in contrast to Fen which can only interact with a single domain proximal to the E3 ligase of AvrPtoB, Pto binds two distinct domains of the effector, the same site as Fen and another N-terminal domain. In the absence of E3 ligase activity Pto binds to either domain of AvrPtoB to activate ETI. However, the presence of an active E3 ligase domain causes ubiquitination of Pto that interacts with the domain proximal to the E3 ligase, identical to ubiquitination of Fen. Only when Pto binds its unique distal domain can it resist AvrPtoB-mediated degradation and activate ETI. We show that phosphorylation of T450 is not required for Pto-mediated resistance in vivo and that a kinase-inactive version of Pto is still capable of activating ETI in response to AvrPtoB. Our results demonstrate that the ability of Pto to interact with a second site distal to the E3 ligase domain in AvrPtoB, and not a higher kinase activity or T450 phosphorylation, allows Pto to evade ubiquitination and to confer immunity to Pst.

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Section: Resultscontrasting

confidence: 99%

Pto Kinase Binds Two Domains of AvrPtoB and Its Proximity to the Effector E3 Ligase Determines if It Evades Degradation and Activates Plant Immunity

2014

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“…Several lines of evidence indicate that a Pto family member encodes Rsb. First, Rsb ‐mediated resistance is Prf dependent, like Pto and the fenthion‐sensitivity gene Fen / PtoB [37]. Second, Rsb is likely present on the Pto locus because RG‐pto11 plants exhibit Rsb ‐mediated resistance, while the near isogenic line RG‐PtoS does not exhibit Rsb ‐mediated resistance [14]; the primary difference between RG‐pto11 and RG‐PtoS is the Pto locus, although, it is possible other unidentified differences exist between these lines.…”

Section: Avrptob Suppresses Programmed Cell Deathmentioning

confidence: 99%

AvrPtoB: A bacterial type III effector that both elicits and suppresses programmed cell death associated with plant immunity

Abramovitch

Martin²

2005

FEMS Microbiology Letters

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Pseudomonas syringae pv. tomato DC3000 is a model pathogen for studying the molecular basis of plant immunity and disease susceptibility in tomato and Arabidopsis. DC3000 uses a type III secretion system to inject effector proteins into the plant cell. Type III effectors are thought to promote bacterial virulence by suppressing plant defenses and enhancing access to nutrients trapped in the plant cell. The AvrPtoB type III effector elicits immunity-associated programmed cell death (PCD) when expressed in tomato plants carrying the Pto resistance protein. However, in the absence of Pto, AvrPtoB functions to suppress PCD and immunity in tomato. Here, we review current research examining the molecular basis of AvrPtoB-mediated elicitation and suppression of plant PCD. In addition, the "trump model" is proposed to explain how resistance proteins successfully elicit immunity-associated PCD in response to effectors that suppress PCD.

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“…For example, the tomato Pto gene belongs to a complex locus consisting of a tightly linked cluster of five to seven genes. Pto confers resistance to Pseudomonas syringae (Martin et al, 1993), whereas the tightly linked paralog Fen confers sensitivity to an organophosphate insecticide (Martin et al, 1994;Loh and Martin, 1995). In other cases, potato Gpa2 and Rx1 share 88.7% homology as paralogs, but they confer resistance to the potato cryst nematode Globodera pallida and potato virus X, respectively (van der Vossen et al, 2000).…”

Section: Functional and Evolutionary Implications For The Slf Proteinmentioning

confidence: 99%

The F-Box Protein AhSLF-S₂ Controls the Pollen Function of S-RNase–Based Self-Incompatibility

et al. 2004

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Recently, we have provided evidence that the polymorphic self-incompatibility (S) locus-encoded F-box (SLF) protein AhSLF-S 2 plays a role in mediating a selective S-RNase destruction during the self-incompatible response in Antirrhinum hispanicum. To investigate its role further, we first transformed a transformation-competent artificial chromosome clone (TAC26) containing both AhSLF-S 2 and AhS 2 -RNase into a self-incompatible (SI) line of Petunia hybrida. Molecular analyses showed that both genes are correctly expressed in pollen and pistil in four independent transgenic lines of petunia. Pollination tests indicated that all four lines became self-compatible because of the specific loss of the pollen function of SI. This alteration was transmitted stably into the T1 progeny. We then transformed AhSLF-S 2 cDNA under the control of a tomato (Lycopersicon esculentum) pollen-specific promoter LAT52 into the self-incompatible petunia line. Molecular studies revealed that AhSLF-S 2 is specifically expressed in pollen of five independent transgenic plants. Pollination tests showed that they also had lost the pollen function of SI. Importantly, expression of endogenous SLF or SLF-like genes was not altered in these transgenic plants. These results phenocopy a well-known phenomenon called competitive interaction whereby the presence of two different pollen S alleles within pollen leads to the breakdown of the pollen function of SI in several solanaceaous species. Furthermore, we demonstrated that AhSLF-S 2 physically interacts with PhS 3 -RNase from the P. hybrida line used for transformation. Together with the recent demonstration of PiSLF as the pollen determinant in P. inflata, these results provide direct evidence that the polymorphic SLF including AhSLF-S 2 controls the pollen function of S-RNase-based self-incompatibility.

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The disease-resistance gene Pto and the fenthion-sensitivity gene fen encode closely related functional protein kinases.

Abstract: Resistance to bacterial speck in tomato is governed by a gene-for-gene interaction in which a single resistance locus (Pto)

Cited by 53 publications

References 33 publications

Pto Kinase Binds Two Domains of AvrPtoB and Its Proximity to the Effector E3 Ligase Determines if It Evades Degradation and Activates Plant Immunity

Pto Kinase Binds Two Domains of AvrPtoB and Its Proximity to the Effector E3 Ligase Determines if It Evades Degradation and Activates Plant Immunity

AvrPtoB: A bacterial type III effector that both elicits and suppresses programmed cell death associated with plant immunity

The F-Box Protein AhSLF-S₂ Controls the Pollen Function of S-RNase–Based Self-Incompatibility

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The disease-resistance gene Pto and the fenthion-sensitivity gene fen encode closely related functional protein kinases.

Abstract: Resistance to bacterial speck in tomato is governed by a gene-for-gene interaction in which a single resistance locus (Pto)

Cited by 53 publications

References 33 publications

Pto Kinase Binds Two Domains of AvrPtoB and Its Proximity to the Effector E3 Ligase Determines if It Evades Degradation and Activates Plant Immunity

Pto Kinase Binds Two Domains of AvrPtoB and Its Proximity to the Effector E3 Ligase Determines if It Evades Degradation and Activates Plant Immunity

AvrPtoB: A bacterial type III effector that both elicits and suppresses programmed cell death associated with plant immunity

The F-Box Protein AhSLF-S2 Controls the Pollen Function of S-RNase–Based Self-Incompatibility

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The F-Box Protein AhSLF-S₂ Controls the Pollen Function of S-RNase–Based Self-Incompatibility