Structural and Functional Analysis of SGT1 Reveals That Its Interaction with HSP90 Is Required for the Accumulation of Rx, an R Protein Involved in Plant Immunity

Botër, Marta; Amigues, Béatrice; Peart, Jack R.; Breuer, Christian; Kadota, Yasuhiro; Casais, Catarina; Moore, Geoffrey R.; Kleanthous, Colin; Ochsenbein, Françoise; Shirasu, Ken; Guérois, Raphaël

doi:10.1105/tpc.107.050427

Cited by 175 publications

(195 citation statements)

References 45 publications

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“…SGT1 is known to be essential for the functioning of many R proteins, likely as part of an essential chaperone complex for R proteins (Austin et al, 2002;Azevedo et al, 2002Azevedo et al, , 2006Botë r et al, 2007). SGT1 has been found in the cytoplasm and also in the nucleus (Noë l et al, 2007) and interacts with chaperones that have been implicated in assisting nuclear shuttling, like HSP90 or HSC70 (Tago et al, 2004;Kose et al, 2005;Brkljacic et al, 2009;Cazalé et al, 2009).…”

Section: Nuclear Localization Of Rx1 Is Impaired Upon Silencing Of Sgt1mentioning

confidence: 99%

“…The induced relocation of Rx1 to the nucleus indicates that in SGT1-silenced plants, Rx1 is still able to take part in the RanGAP2 interaction and can enter the nucleus if directed there via the nuclear import system. SGT1 forms a chaperone complex with RAR1 and HSP90, which is essential for NB-LRR protein folding and stability (Takahashi et al, 2003;Holt et al, 2005;Botë r et al, 2007;Shirasu, 2009). The chaperone function of SGT1 and RAR1 for NB-LRR proteins has earlier been associated with the LRR domain; for example, the RAR1 dependence of barley MLA variants is determined by their LRR (Bieri et al, 2004).…”

Section: The CC and Lrr Domains Play Distinct Roles In The Nucleocytomentioning

confidence: 99%

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Nucleocytoplasmic Distribution Is Required for Activation of Resistance by the Potato NB-LRR Receptor Rx1 and Is Balanced by Its Functional Domains

Slootweg¹,

Roosien²,

et al. 2010

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The Rx1 protein, as many resistance proteins of the nucleotide binding-leucine-rich repeat (NB-LRR) class, is predicted to be cytoplasmic because it lacks discernable nuclear targeting signals. Here, we demonstrate that Rx1, which confers extreme resistance to Potato virus X, is located both in the nucleus and cytoplasm. Manipulating the nucleocytoplasmic distribution of Rx1 or its elicitor revealed that Rx1 is activated in the cytoplasm and cannot be activated in the nucleus. The coiled coil (CC) domain was found to be required for accumulation of Rx1 in the nucleus, whereas the LRR domain promoted the localization in the cytoplasm. Analyses of structural subdomains of the CC domain revealed no autonomous signals responsible for active nuclear import. Fluorescence recovery after photobleaching and nuclear fractionation indicated that the CC domain binds transiently to large complexes in the nucleus. Disruption of the Rx1 resistance function and protein conformation by mutating the ATP binding phosphate binding loop in the NB domain, or by silencing the cochaperone SGT1, impaired the accumulation of Rx1 protein in the nucleus, while Rx1 versions lacking the LRR domain were not affected in this respect. Our results support a model in which interdomain interactions and folding states determine the nucleocytoplasmic distribution of Rx1.

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Section: Nuclear Localization Of Rx1 Is Impaired Upon Silencing Of Sgt1mentioning

confidence: 99%

Section: The CC and Lrr Domains Play Distinct Roles In The Nucleocytomentioning

confidence: 99%

Nucleocytoplasmic Distribution Is Required for Activation of Resistance by the Potato NB-LRR Receptor Rx1 and Is Balanced by Its Functional Domains

Slootweg¹,

Roosien²,

et al. 2010

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“…Null eds1 mutants of A. thaliana are not able to generate the resistance response even if they contain autoactivation mutations within genes encoding TIR-NBS-LRR proteins [90]. The necrotrophic fungus Botrytis cinerea can manipulate the plant signal transduction pathway via the activation of the EDS1 and SGT1 genes, thus triggering cell death [96]. In A. thaliana, SGT1 (the suppressor of the G2 allele of skp1) seems to affect the regulation of resistance processes that are initiated both by TIR-NBS-LRR proteins such as RPP2 and RPP4, conditioning resistance to P. parasitica, as well as non-TIR-NBS-LRR such as RPP7 and MLA, conditioning the resistance of barley to Blumeria graminis [93,94].…”

Section: R Proteins-mediated Signaling Pathwaymentioning

confidence: 99%

R proteins as fundamentals of plant innate immunity

Głowacki

Macioszek

Kononowicz

2011

Cellular and Molecular Biology Letters

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Abstract:Plants are attacked by a wide spectrum of pathogens, being the targets of viruses, bacteria, fungi, protozoa, nematodes and insects. Over the course of their evolution, plants have developed numerous defense mechanisms including the chemical and physical barriers that are constitutive elements of plant cell responses locally and/or systemically. However, the modern approach in plant sciences focuses on the evolution and role of plant protein receptors corresponding to specific pathogen effectors. The recognition of an invader's molecules could be in most cases a prerequisite sine qua non for plant survival. Although the predicted three-dimensional structure of plant resistance proteins (R) is based on research on their animal homologs, advanced technologies in molecular biology and bioinformatics tools enable the investigation or prediction of interaction mechanisms for specific receptors with pathogen effectors. Most of the identified R proteins belong to the NBS-LRR family. The presence of other domains (including the TIR domain) apart from NBS and LRR is fundamental for the classification of R proteins into subclasses. Recently discovered additional domains (e.g. WRKY) of R proteins allowed the examination of their localization in plant cells and the role they play in signal transduction during the plant resistance response to biotic stress factors. This review focuses on the current state of knowledge about the NBS-LRR family of plant R proteins: their structure, function and evolution, and the role they play in plant innate immunity.

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“…The interaction of SGT1 with HSP90 has been shown to be required for SGT1 function (6). Mutation of SGT1 can suppress rar1 for some NB-LRR functions, but not all (7).…”

mentioning

confidence: 99%

Specific Arabidopsis HSP90.2 alleles recapitulate RAR1 cochaperone function in plant NB-LRR disease resistance protein regulation

Hubert¹,

He²,

McNulty³

et al. 2009

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

100

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Both plants and animals require the activity of proteins containing nucleotide binding (NB) domain and leucine-rich repeat (LRR)domains for proper immune system function. NB-LRR proteins in plants (NLR proteins in animals) also require conserved regulation via the proteins SGT1 and cytosolic HSP90. RAR1, a protein specifically required for plant innate immunity, interacts with SGT1 and HSP90 to maintain proper NB-LRR protein steady-state levels. Here, we present the identification and characterization of specific mutations in Arabidopsis HSP90.2 that suppress all known phenotypes of rar1. These mutations are unique with respect to the many mutant alleles of HSP90 identified in all systems in that they can bypass the requirement for a cochaperone and result in the recovery of client protein accumulation and function. Additionally, these mutations separate HSP90 ATP hydrolysis from HSP90 function in client protein folding and/or accumulation. By recapitulating the activity of RAR1, these novel hsp90 alleles allow us to propose that RAR1 regulates the physical open-close cycling of a known ''lid structure'' that is used as a dynamic regulatory HSP90 mechanism. Thus, in rar1, lid cycling is locked into a conformation favoring NB-LRR client degradation, likely via SGT1 and the proteasome.innate immunity ͉ Pseudomonas syringae ͉ SGT1 ͉ STAND ATPase protein P lants have evolved a highly complex immune system centered on pathogen recognition via the evolutionarily-conserved NB-LRR proteins. Pathogen-triggered activation of NB-LRR proteins leads to several responses, including cell wall strengthening, transcriptional reprogramming, and a form of programmed cell death termed the hypersensitive response (HR). Because their function often results in cell death, proper maintenance of NB-LRR protein levels and activation state are vital to the health of the plant (1).NB-LRR proteins can be divided into 2 structural subgroups based on the presence of either a likely coiled-coil (CC) or Toll interleukin-1 receptor (TIR) domain at their N termini. Either of these N-terminal domains is followed in both subgroups by a middle nucleotide binding (NB) site and a C-terminal leucine-rich repeat (LRR). This general structure is not only conserved across all plants but extends to NOD/Caterpiller/NLR proteins that mediate various processes in mammalian innate immunity (2).Just as the domain composition of these intracellular receptors is conserved from plants to animals, so is the regulation of their steady-state accumulation. Cytosolic HSP90 and the cochaperone SGT1 have been previously demonstrated to not only be important for regulation of NB-LRR proteins in plants, but also in regulation of NLR function in animals (3). A third protein called RAR1 appears to play a role in innate immunity specifically in plants (4).All 3 of these proteins can independently interact with one another; the CS domain of SGT1b, or the CHORDI domain of RAR1, can interact with the N-terminal ATPase domain of HSP90; the CHORDII domain of RAR1 also interacts wi...

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Structural and Functional Analysis of SGT1 Reveals That Its Interaction with HSP90 Is Required for the Accumulation of Rx, an R Protein Involved in Plant Immunity

Cited by 175 publications

References 45 publications

Nucleocytoplasmic Distribution Is Required for Activation of Resistance by the Potato NB-LRR Receptor Rx1 and Is Balanced by Its Functional Domains

Nucleocytoplasmic Distribution Is Required for Activation of Resistance by the Potato NB-LRR Receptor Rx1 and Is Balanced by Its Functional Domains

R proteins as fundamentals of plant innate immunity

Specific Arabidopsis HSP90.2 alleles recapitulate RAR1 cochaperone function in plant NB-LRR disease resistance protein regulation

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