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The two Dps proteins, NpDps2 and NpDps5, are involved in light-induced oxidative stress tolerance in the N2-fixing cyanobacterium Nostoc punctiforme
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Univ Copenhagen, Dept Plant & Environm Sci, CPSC, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Umea Univ, Dept Mol Biol, 6K & 6L Sjukhusomradet, S-90187 Umea, Sweden.
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2016 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1857, p. 1766-1776Article in journal (Refereed) Published
Abstract [en]

Cyanobacteria are photosynthetic prokaryotes that are considered biotechnologically prominent organisms for production of high-value compounds. Cyanobacteria are subject to high-light intensities, which is a challenge that needs to be addressed in design of efficient bio-engineered photosynthetic organisms. Dps proteins are members of the ferritin superfamily and are omnipresent in prokaryotes. They play a major role in oxidative stress protection and iron homeostasis. The filamentous, heterocyst-forming Nostoc punctiforme, has five Dps proteins. In this study we elucidated the role of these Dps proteins in acclimation to high light intensity, the gene loci organization and the transcriptional regulation of all five dps genes in N. punctiforme was revealed, and dps-deletion mutant strains were used in physiologica characterization. Two mutants defective in Dps2 and Dps5 activity displayed a reduced fitness under increased illumination, as well as a differential Photosystem (PS) stoichiometry, with an elevated Photosystem II to Photosystem I ratio in the dps5 deletion strain. This work establishes a Dps-mediated link between light tolerance,H2O2 detoxification, and iron homeostasis, and provides further evidence on the non-redundant role of multiple Dps proteins in this multicellular cyanobacterium.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 1857, p. 1766-1776
Keyword [en]
adaptation; cyanobacteria; ferritin; photosystem; light-stress; ROS
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:uu:diva-301875DOI: 10.1016/j.bbabio.2016.08.003ISI: 000384867400006OAI: oai:DiVA.org:uu-301875DiVA, id: diva2:955491
Funder
Swedish Energy Agency, 11674-5Knut and Alice Wallenberg Foundation, 2011.0067Carl Tryggers foundation Lars Hierta Memorial Foundation
Available from: 2016-08-25 Created: 2016-08-25 Last updated: 2018-03-01Bibliographically approved
In thesis
1. Development of robust cyanobacterial strains for biotechnological applications: Stress tolerance and cell-specific expression in heterocyst-forming cyanobacteria
Open this publication in new window or tab >>Development of robust cyanobacterial strains for biotechnological applications: Stress tolerance and cell-specific expression in heterocyst-forming cyanobacteria
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Synthetic biology tools can be used to exploit potential applications of cyanobacteria, promising photosynthetic hosts for production of fuels and chemicals. Specific genetic tools are needed for the development of robust cyanobacterial strains for bioengineering. The key work presented in this thesis is a characterization and design of bioengineering tools for the heterocyst-forming cyanobacterium Nostoc punctiforme strain ATCC 29133. This multicellular cyanobacterium may express several oxidative stress-managing systems, including five Dps proteins. Two of these Dps proteins, NpDps2 and NpDps5, are involved in the tolerance against oxidative stress that induced by H2O2 or high light intensities. The capacity of NpDps2 and NpDps5 to further enhance oxidative stress tolerance, was confirmed by homologous overexpression and a constitutive strong promoter in N. punctiforme. The results show the potential of Dps proteins as tools to create robust cyanobacterial cells with improved stress tolerance. This work also establishes a Dps-mediated link among light tolerance, H2O2 scavenging, and iron homeostasis, and provides evidence on the non-redundant role of multiple Dps in multicellular cyanobacteria. To address the lack of well-defined promoters in cyanobacteria, a minimal synthetic promoter, SynDIF, was designed for heterocyst-specific expression. Promoters with 5’TCCGGA, the DIF motif, at the -35 region, have been identified to give heterocyst-specific transcription. To identify promoter elements, critical for cell-specificity, DIF promoter sequences from Anabaena PCC 7120 were used in a consensus sequence approach. The importance of the consensus regions for cell-specificity was investigated with promoter-eyfp reporters. This result provides new insights to the details of DIF promoters, which suggest that the DIF-motif, only together with the consensus or a native DIF promoter -10 region, are sufficient for heterocyst-specificity. Therefore, the DIF-35 region was (i) not independent of other promoter elements, and (ii) not sufficient for heterocyst-specific expression. Besides, the strength of the synthetic promoter was improved by including the upstream element from the native heterocyst specific promoter PNsiR1. Moreover, the SynDIF promoter is the shortest promoter ever reported to provide heterocyst-specific expression, indicating the potential of introducing this promoter in future biotechnological applications.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 80
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1641
Keyword
Cyanobacteria,  Dps protein,  heterocysts,  Nostoc,  oxidative stress,  cell specific promoter, ROS tolerance, synthetic biology tools transcriptional regulation.
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
urn:nbn:se:uu:diva-343829 (URN)978-91-513-0259-1 (ISBN)
Public defence
2018-04-20, 10134, Polhemsalen, Lägerhyddsvägen 1, Ångström Laboratory, Uppsala, 13:15 (English)
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Supervisors
Available from: 2018-03-26 Created: 2018-03-01 Last updated: 2018-04-24

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