Only one dnaK homolog, dnaK2, is active transcriptionally and is essential in Synechocystis

Varvasovszki, Viktória; Glatz, Attila; Shigapova, Natalia; Jósvay, Katalin; Vı́gh, László; Horváth, Ibolya

doi:10.1016/s0006-291x(03)00822-2

Cited by 17 publications

(10 citation statements)

References 33 publications

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“…Although some of the chaperone genes like dnaK2 , htpG or hspA have been described to be up-regulated after several stress conditions [37], [38], [39], [40], [41], [42], a general induction of this group has not been previously described. Recently, it has been shown that arsenite is able to inhibit nascent protein folding both in vitro and in vivo in yeast [13], [14], [15] and Archea [15].…”

Section: Resultsmentioning

confidence: 97%

Genomic Responses to Arsenic in the Cyanobacterium Synechocystis sp. PCC 6803

2014

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Arsenic is a ubiquitous contaminant and a toxic metalloid which presents two main redox states in nature: arsenite [AsIII] and arsenate [AsV]. Arsenic resistance in Synechocystis sp. strain PCC 6803 is mediated by the arsBHC operon and two additional arsenate reductases encoded by the arsI1 and arsI2 genes. Here we describe the genome-wide responses to the presence of arsenate and arsenite in wild type and mutants in the arsenic resistance system. Both forms of arsenic produced similar responses in the wild type strain, including induction of several stress related genes and repression of energy generation processes. These responses were transient in the wild type strain but maintained in time in an arsB mutant strain, which lacks the arsenite transporter. In contrast, the responses observed in a strain lacking all arsenate reductases were somewhat different and included lower induction of genes involved in metal homeostasis and Fe-S cluster biogenesis, suggesting that these two processes are targeted by arsenite in the wild type strain. Finally, analysis of the arsR mutant strain revealed that ArsR seems to only control 5 genes in the genome. Furthermore, the arsR mutant strain exhibited hypersentivity to nickel, copper and cadmium and this phenotype was suppressed by mutation in arsB but not in arsC gene suggesting that overexpression of arsB is detrimental in the presence of these metals in the media.

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Section: Resultsmentioning

confidence: 97%

Genomic Responses to Arsenic in the Cyanobacterium Synechocystis sp. PCC 6803

2014

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“…PCC 6803 (Kanesaki et al, 2002). The expression of DnaK2, also known as heat-shock protein hsp70-2, is also known to be induced by stress conditions including salt, UV light and heat stress (Varvasovszki et al, 2003;Mary et al, 2004;Fulda et al, 2006).…”

Section: Resultsmentioning

confidence: 99%

Microarray analysis of phosphate regulation in the marine cyanobacterium Synechococcus sp. WH8102

et al. 2009

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Primary productivity of open ocean environments, such as those inhabited by marine picocyanobacteria, is often limited by low inorganic phosphate (P). To observe how these organisms cope with P starvation, we constructed a full genome microarray for Synechococcus sp. WH8102 and compared differences in gene expression under P-replete and P-limited growth conditions, including both early P stress, during extracellular alkaline phosphatase induction, and late P stress. A total of 36 genes showed significant upregulation (4log 2 fold) whereas 23 genes were highly downregulated at the early time point; however, these changes in expression were maintained during late P stress for only 5 of the upregulated genes. Knockout mutants were constructed for genes SYNW0947 and SYNW0948, comprising a two-component regulator hypothesized to have a key function in regulating P metabolism. A high degree of overlap in the sets of genes affected by P stress conditions and in the knockout mutants supports this hypothesis; however, there is some indication that other regulators may be involved in this response in Synechococcus sp. WH8102. Consistent with what has been observed in many other cyanobacteria, the Pho regulon of this strain is comprised largely of genes for alkaline phosphatases, P transport or P metabolism. Interestingly, however, the exact composition and arrangement of the Pho regulon appears highly variable in marine cyanobacteria.

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“…Multiple dnaK and dnaJ genes have also been reported for Escherichia coli (Genevaux et al, 2007). Of the three dnaK genes in the unicellular cyanobacteria, only dnaK2 is induced under heat and other abiotic stresses (Rupprecht et al, 2010;Sato et al, 2007) and contributes to thermotolerance (Varvasovszki et al, 2003). Among the seven DnaJ proteins, the one encoded by sll0897 (DnaJ2) has been suggested to be the canonical Hsp (Düppre et al, 2011).…”

Section: The Hsr In Cyanobacteriamentioning

confidence: 99%

Cyanobacterial heat-shock response: role and regulation of molecular chaperones

2014

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Cyanobacteria constitute a morphologically diverse group of oxygenic photoautotrophic microbes which range from unicellular to multicellular, and non-nitrogen-fixing to nitrogen-fixing types. Sustained long-term exposure to changing environmental conditions, during their three billion years of evolution, has presumably led to their adaptation to diverse ecological niches. The ability to maintain protein conformational homeostasis (folding-misfolding-refolding or aggregationdegradation) by molecular chaperones holds the key to the stress adaptability of cyanobacteria. Although cyanobacteria possess several genes encoding DnaK and DnaJ family proteins, these are not the most abundant heat-shock proteins (Hsps), as is the case in other bacteria. Instead, the Hsp60 family of proteins, comprising two phylogenetically conserved proteins, and small Hsps are more abundant during heat stress. The contribution of the Hsp100 (ClpB) family of proteins and of small Hsps in the unicellular cyanobacteria (Synechocystis and Synechococcus) as well as that of Hsp60 proteins in the filamentous cyanobacteria (Anabaena) to thermotolerance has been elucidated. The regulation of chaperone genes by several cis-elements and trans-acting factors has also been well documented. Recent studies have demonstrated novel transcriptional and translational (mRNA secondary structure) regulatory mechanisms in unicellular cyanobacteria. This article provides an insight into the heat-shock response: its organization, and ecophysiological regulation and role of molecular chaperones, in unicellular and filamentous nitrogen-fixing cyanobacterial strains.

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Only one dnaK homolog, dnaK2, is active transcriptionally and is essential in Synechocystis

Cited by 17 publications

References 33 publications

Genomic Responses to Arsenic in the Cyanobacterium Synechocystis sp. PCC 6803

Genomic Responses to Arsenic in the Cyanobacterium Synechocystis sp. PCC 6803

Microarray analysis of phosphate regulation in the marine cyanobacterium Synechococcus sp. WH8102

Cyanobacterial heat-shock response: role and regulation of molecular chaperones

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