Mitochondrial Small Heat Shock Proteins Are Essential for Normal Growth of Arabidopsis thaliana

Mitochondria play important roles in the plant stress responses and the detoxification of the reactive oxygen species generated in the electron transport chain. Expression of genes encoding stress-related proteins such as the mitochondrial small heat shock proteins (M-sHSP) is upregulated in response to different abiotic stresses. In Arabidopsis thaliana, three M-sHSPs paralogous genes were identified, although their function under physiological conditions remains elusive. The aim of this work is to uncover the in vivo function of all three M-sHSPs at the whole plant level. To accomplish this goal, we analyzed the phenotype, proteomic, and metabolic profiles of Arabidopsis knock-down lines of M-sHSPs (single, double, and triple knock-down lines) during normal plant growth. The triple knock-down plants showed the most prominent altered phenotype at vegetative and reproductive stages without any externally applied stress. They displayed chlorotic leaves, growth arrest, and low seed production. Concomitantly, they exhibited increased levels of sugars, proline, and citric, malic, and ascorbic acid, among other metabolites. In contrast, single and double knock-down plants displayed a few changes in their phenotype. A redundant function among the three M-sHSPs is indicated by the impairment in vegetative and reproductive growth associated with the simultaneous loss of all three M-sHSPs genes. The triple knock-down lines showed alteration of proteins mainly involved in photosynthesis and antioxidant defense compared to the control plants. On the other hand, heat stress triggered a distinct cytosolic response pattern and the upregulation of other sHSP members, in the knock-down plants. Overall, depletion of all three M-sHSPs in Arabidopsis severely impacted fundamental metabolic processes, leading to alterations in the correct plant growth and development. These findings expand our knowledge about the contribution of organelle-specific M-sHSPs to healthy plant growth under non-stress conditions.

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In vivo evidence from an Agrostis stolonifera selection genotype that chloroplast small heat-shock proteins can protect photosystem II during heat stress

Functional Plant Biology ◽

10.1071/pp01191 ◽

2002 ◽

Vol 29 (8) ◽

pp. 935 ◽

Cited By ~ 70

Author(s):

Scott A. Heckathorn ◽

Samantha L. Ryan ◽

Joanne A. Baylis ◽

Dongfang Wang ◽

E. William Hamilton III ◽

...

Keyword(s):

Heat Stress ◽

Electron Transport ◽

Heat Shock ◽

Heat Shock Proteins ◽

Agrostis Stolonifera ◽

Small Heat Shock Proteins ◽

O2 Evolution ◽

Shock Proteins ◽

Tolerant Genotype

Previous in vitro experiments indicated that chloroplast small heat-shock proteins (sHsp) could associate with thylakoids and protect PSII during heat and other stresses, possibly by stabilizing the O2-evolving complex (OEC). However, in vivo evidence of sHsp protection of PSII is equivocal at present. Using previously characterized selection genotypes of Agrostis stolonifera Huds. that differ in thermotolerance and production of chloroplast sHsps, we show that both genotypes contain thylakoid-associating sHsps, but the heat-tolerant genotype, which produces an additional sHsp isoform not made by the sensitive genotype, produces a greater quantity of chloroplast and thylakoid sHsp. Following a pre-heat stress to induce sHsps, in vivo PSII function decreased less at high temperatures in the tolerant genotype. Differences in PSII thermotolerance in vivo were associated with increased thermotolerance of the OEC proteins and O2-evolving function of PSII, and not with other PSII proteins or functions examined. In vivo cross-linking experiments indicated that a greater amount of sHsp associated with PSII proteins during heat stress in the tolerant genotype. PSII was the most thermosensitive component of photosynthetic electron transport, and no differences between genotypes in the thermotolerance of other electron transport components were observed. These results indicate that in vivo chloroplast sHsps can protect O2 evolution and the OEC proteins of PSII during heat stress.

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Characterization of two genes encoding small heat-shock proteins in Arabidopsis thaliana

MGG Molecular & General Genetics ◽

10.1007/bf00259608 ◽

1989 ◽

Vol 219 (3) ◽

pp. 365-372 ◽

Cited By ~ 57

Author(s):

Taku Takahashi ◽

Yoshibumi Komeda

Keyword(s):

Arabidopsis Thaliana ◽

Heat Shock ◽

Heat Shock Proteins ◽

Small Heat Shock Proteins ◽

Genes Encoding ◽

Shock Proteins

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Cellular Functions and Mechanisms of Action of Small Heat Shock Proteins

Annual Review of Microbiology ◽

10.1146/annurev-micro-020518-115515 ◽

2019 ◽

Vol 73 (1) ◽

pp. 89-110 ◽

Cited By ~ 35

Author(s):

Axel Mogk ◽

Carmen Ruger-Herreros ◽

Bernd Bukau

Keyword(s):

Heat Shock ◽

Heat Shock Proteins ◽

Protein Unfolding ◽

Small Heat Shock Proteins ◽

Cellular Functions ◽

Independent Manner ◽

Cellular Defense ◽

Shock Proteins ◽

Substrate Binding Sites

Small heat shock proteins (sHsps) constitute a diverse chaperone family that shares the α-crystallin domain, which is flanked by variable, disordered N- and C-terminal extensions. sHsps act as the first line of cellular defense against protein unfolding stress. They form dynamic, large oligomers that represent inactive storage forms. Stress conditions cause a rapid increase in cellular sHsp levels and trigger conformational rearrangements, resulting in exposure of substrate-binding sites and sHsp activation. sHsps bind to early-unfolding intermediates of misfolding proteins in an ATP-independent manner and sequester them in sHsp/substrate complexes. Sequestration protects substrates from further uncontrolled aggregation and facilitates their refolding by ATP-dependent Hsp70-Hsp100 disaggregases. Some sHsps with particularly strong sequestrase activity, such as yeast Hsp42, are critical factors for forming large, microscopically visible deposition sites of misfolded proteins in vivo. These sites are organizing centers for triaging substrates to distinct quality control pathways, preferentially Hsp70-dependent refolding and selective autophagy.

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The Escherichia coli small heat-shock proteins IbpA and IbpB prevent the aggregation of endogenous proteins denatured in vivo during extreme heat shock

Microbiology ◽

10.1099/00221287-148-6-1757 ◽

2002 ◽

Vol 148 (6) ◽

pp. 1757-1765 ◽

Cited By ~ 64

Author(s):

Dorota Kuczynska-Wisnik ◽

Sabina Kçdzierska ◽

Ewelina Matuszewska ◽

Peter Lund ◽

Alina Taylor ◽

...

Keyword(s):

Escherichia Coli ◽

Heat Shock ◽

Heat Shock Proteins ◽

Small Heat Shock Proteins ◽

Extreme Heat ◽

Endogenous Proteins ◽

Shock Proteins

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Small Hsps as Therapeutic Targets of Cystic Fibrosis Transmembrane Conductance Regulator Protein

International Journal of Molecular Sciences ◽

10.3390/ijms22084252 ◽

2021 ◽

Vol 22 (8) ◽

pp. 4252

Author(s):

Stéphanie Simon ◽

Abdel Aissat ◽

Fanny Degrugillier ◽

Benjamin Simonneau ◽

Pascale Fanen ◽

...

Keyword(s):

Cystic Fibrosis ◽

Heat Shock ◽

Heat Shock Proteins ◽

Small Heat Shock Proteins ◽

Transmembrane Conductance Regulator ◽

Transmembrane Conductance ◽

Regulator Protein ◽

Shock Proteins ◽

Cystic Fibrosis Transmembrane

Human small heat shock proteins are molecular chaperones that regulate fundamental cellular processes in normal and pathological cells. Here, we have reviewed the role played by HspB1, HspB4 and HspB5 in the context of Cystic Fibrosis (CF), a severe monogenic autosomal recessive disease linked to mutations in Cystic Fibrosis Transmembrane conductance Regulator protein (CFTR) some of which trigger its misfolding and rapid degradation, particularly the most frequent one, F508del-CFTR. While HspB1 and HspB4 favor the degradation of CFTR mutants, HspB5 and particularly one of its phosphorylated forms positively enhance the transport at the plasma membrane, stability and function of the CFTR mutant. Moreover, HspB5 molecules stimulate the cellular efficiency of currently used CF therapeutic molecules. Different strategies are suggested to modulate the level of expression or the activity of these small heat shock proteins in view of potential in vivo therapeutic approaches. We then conclude with other small heat shock proteins that should be tested or further studied to improve our knowledge of CFTR processing.

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Roles of the Escherichia coli Small Heat Shock Proteins IbpA and IbpB in Thermal Stress Management: Comparison with ClpA, ClpB, and HtpG In Vivo

Journal of Bacteriology ◽

10.1128/jb.180.19.5165-5172.1998 ◽

1998 ◽

Vol 180 (19) ◽

pp. 5165-5172 ◽

Cited By ~ 130

Author(s):

Jeffrey G. Thomas ◽

François Baneyx

Keyword(s):

Escherichia Coli ◽

Heat Shock ◽

Heat Shock Proteins ◽

High Temperatures ◽

Small Heat Shock Proteins ◽

Host Protein ◽

E Coli ◽

Growth Defects ◽

Shock Proteins

ABSTRACT We have constructed an Escherichia coli strain lacking the small heat shock proteins IbpA and IbpB and compared its growth and viability at high temperatures to those of isogenic cells containing null mutations in the clpA, clpB, orhtpG gene. All mutants exhibited growth defects at 46°C, but not at lower temperatures. However, the clpA,htpG, and ibp null mutations did not reduce cell viability at 50°C. When cultures were allowed to recover from transient exposure to 50°C, all mutations except Δibpled to suboptimal growth as the recovery temperature was raised. Deletion of the heat shock genes clpB and htpGresulted in growth defects at 42°C when combined with thednaK756 or groES30 alleles, while the Δibp mutation had a detrimental effect only on the growth of dnaK756 mutants. Neither the overexpression of these heat shock proteins nor that of ClpA could restore the growth ofdnaK756 or groES30 cells at high temperatures. Whereas increased levels of host protein aggregation were observed indnaK756 and groES30 mutants at 46°C compared to wild-type cells, none of the null mutations had a similar effect. These results show that the highly conserved E. coli small heat shock proteins are dispensable and that their deletion results in only modest effects on growth and viability at high temperatures. Our data also suggest that ClpB, HtpG, and IbpA and -B cooperate with the major E. coli chaperone systems in vivo.

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Exploring Small Heat Shock Proteins (sHSPs) for Targeting Drug Resistance in Candida albicans and other Pathogenic Fungi

Journal of Pure and Applied Microbiology ◽

10.22207/jpam.15.1.42 ◽

2021 ◽

Vol 15 (1) ◽

pp. 20-28

Author(s):

Rahul Dev

Keyword(s):

Heat Shock ◽

Heat Shock Proteins ◽

Stress Responses ◽

Drug Targets ◽

Fungal Infections ◽

Small Heat Shock Proteins ◽

Antifungal Drugs ◽

Antifungal Drug ◽

Drug Induced ◽

Shock Proteins

Fungal infections have predominantly increased worldwide that leads to morbidity and mortality in severe cases. Invasive candidiasis and other pathogenic fungal infections are a major problem in immunocompromised individuals and post-operative patients. Increasing resistance to existing antifungal drugs calls for the identification of novel antifungal drug targets for chemotherapeutic interventions. This demand for identification and characterization of novel drug targets leads to the development of effective antifungal therapy against drug resistant fungi. Heat shock proteins (HSPs) are important for various biological processes like protein folding, posttranslational modifications, transcription, translation, and protein aggregation. HSPs are involved in maintaining homeostasis of the cell. A subgroup of HSPs is small heat shock proteins (sHSPs), which functions as cellular chaperones. They are having a significant role in the many cellular functions like development, cytoskeletal organization, apoptosis, membrane lipid polymorphism, differentiation, autophagy, in infection recognition and are major players in various stresses like osmotic stress, pH stress, etc. Studies have shown that fungal cells express increased levels of sHSPs upon antifungal drug induced stress responses. Here we review the important role of small heat shock proteins (sHSPs) in fungal diseases and their potential as antifungal targets.

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