The Small Heat-shock Protein HspL Is a VirB8 Chaperone Promoting Type IV Secretion-mediated DNA Transfer

Tsai, Yun-Long; Chiang, Yin-Ru; Narberhaus, Franz; Baron, Christian; Lai, Erh‐Min

doi:10.1074/jbc.m110.110296

Cited by 22 publications

(24 citation statements)

References 58 publications

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“…While the majority of T4SS components can be assembled into subcomplexes when expressed in a heterologous E. coli system, an alpha-crystallin-type small heat shock protein, HspL was shown to be important for stability of several VirB proteins and efficient T-DNA transfer and tumorigenesis (Tsai et al, 2009). HspL expression is induced by AS in response to VirB protein expression and functions as a VirB8 chaperone (Tsai et al, 2009(Tsai et al, , 2010. Moreover, overexpression of HspL in A. tumefaciens enhanced transient transformation efficiencies of both susceptible and recalcitrant Arabidopsis ecotypes.…”

Section: Transport Of T-dna and Virulence Proteins Via Type IV Secretmentioning

confidence: 99%

“…Several studies have utilized quantitative root transformation assays to determine virulence of different A. tumefaciens strains and relative transformation efficiencies of different A. thaliana mutants or ecotypes. Based on the results obtained from these root transformation assays, bacterial and plant proteins that are involved in Agrobacterium-mediated plant transformation process can be identified and characterized; several of these were described above (Nam et al, 1997Bundock et al, 1999Mysore et al, 2000a;Zhu et al, 2003aZhu et al, , 2003bTsai et al, 2009;Gelvin, 2010aGelvin, , 2010bHwang et al, 2010;Tsai et al, 2010;Gelvin, 2012;Hwang et al, 2013bHwang et al, , 2015.…”

Section: Stable Transformation Using Root Explantsmentioning

confidence: 99%

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Agrobacterium-Mediated Plant Transformation: Biology and Applications

Hwang

Lai

2017

The Arabidopsis Book

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Section: Transport Of T-dna and Virulence Proteins Via Type IV Secretmentioning

confidence: 99%

Section: Stable Transformation Using Root Explantsmentioning

confidence: 99%

Agrobacterium-Mediated Plant Transformation: Biology and Applications

Hwang

Lai

2017

The Arabidopsis Book

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232

142

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“…Thus, we overexpressed and purified all four sHsps tagged with 6xHis in E. coli and determined their chaperone activities by a thermal aggregation protection assay [26]. The results show that all four sHsps are equally efficient in protecting the model substrate citrate synthase (CS) from thermal aggregation in vitro (Figure 4A).…”

Section: Resultsmentioning

confidence: 99%

One out of Four: HspL but No Other Small Heat Shock Protein of Agrobacterium tumefaciens Acts as Efficient Virulence-Promoting VirB8 Chaperone

Tsai

Chiang

et al. 2012

PLoS ONE

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Alpha-crystallin-type small heat shock proteins (sHsps) are ubiquitously distributed in most eukaryotes and prokaryotes. Four sHsp genes named hspL, hspC, hspAT1, and hspAT2 were identified in Agrobacterium tumefaciens, a plant pathogenic bacterium capable of unique interkingdom DNA transfer via type IV secretion system (T4SS). HspL is highly expressed in virulence-induced growth condition and functions as a VirB8 chaperone to promote T4SS-mediated DNA transfer. Here, we used genetic and biochemical approaches to investigate the involvement of the other three sHsps in T4SS and discovered the molecular basis underlying the dominant function of HspL in promoting T4SS function. While single deletion of hspL but no other sHsp gene reduced T4SS-mediated DNA transfer and tumorigenesis efficiency, additional deletion of other sHsp genes in the hspL deletion background caused synergistic effects in the virulence phenotypes. This is correlated with the high induction of hspL and only modest increase of hspC, hspAT1, and hspAT2 at their mRNA and protein abundance in virulence-induced growth condition. Interestingly, overexpression of any single sHsp gene alone in the quadruple mutant caused increased T4SS-mediated DNA transfer and tumorigenesis. Thermal aggregation protecting assays in vitro indicated that all four sHsps exhibit chaperone activity for the model substrate citrate synthase but only HspL functions as efficient chaperone for VirB8. The higher VirB8 chaperone activity of HspL was also demonstrated in vivo, in which lower amounts of HspL than other sHsps were sufficient in maintaining VirB8 homeostasis in A. tumefaciens. Domain swapping between HspL and HspAT2 indicated that N-terminal, central alpha-crystallin, and C-terminal domains of HspL all contribute to HspL function as an efficient VirB8 chaperone. Taken together, we suggest that the dominant role of HspL in promoting T4SS function is based on its higher expression in virulence-induced condition and its more efficient VirB8 chaperone activity as compared to other sHsps.

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“…In Bacillus subtilis, an ACD-containing sHSP (CotM) was identified as a spore coat protein (108,109). The plant pathogen A. tumefaciens uses HspL as virulence promoting factor (110)(111)(112). Thus sHSPs exert pleiotropic effects throughout the life and it cannot be excluded that new functions will be discovered.…”

Section: Localization and Physiological Relevancementioning

confidence: 99%

Small heat shock proteins: recent developments

Eisenhardt

2013

BioMolecular Concepts

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Small heat shock proteins (sHSPs) are abundantly present in many different organisms at elevated temperatures. Members of the subgroup of alpha crystallin domain (ACD)-type sHSPs belong to the large family of protein chaperones. They bind non-native proteins in an ATP-independent manner, thereby holding the incorporated clients soluble for subsequent refolding by other molecular chaperoning systems. sHSPs do not actively refold incorporated peptides therefore they are sometimes referred to as holdases. Varying numbers of sHSPs have been documented in the different domains of life and dependent on the analyzed organism. Generally, diverse sHSPs possess more sequence similarities in the conserved ACD, whereas the N- and C-terminal extensions are less conserved. Despite their designation as sHSPs, they are not solely present during heat stress. sHSPs presumably help to protect cells under various stresses, but they were also found during development, e.g., in embryonic development of higher plants which is associated with ongoing seed desiccation. The functional and physiological relevance of several different sHSPs in one organism remains still unclear, especially in plants where several highly similar sHSPs are present in the same compartment. The wide range of biotic and abiotic stresses that induce the expression of multiple sHSP genes makes it challenging to define the physiological relevance of each of these versatile proteins.

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The Small Heat-shock Protein HspL Is a VirB8 Chaperone Promoting Type IV Secretion-mediated DNA Transfer

Cited by 22 publications

References 58 publications

Agrobacterium-Mediated Plant Transformation: Biology and Applications

Agrobacterium-Mediated Plant Transformation: Biology and Applications

One out of Four: HspL but No Other Small Heat Shock Protein of Agrobacterium tumefaciens Acts as Efficient Virulence-Promoting VirB8 Chaperone

Small heat shock proteins: recent developments

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