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Differential transcriptional regulation of orthologous dps genes from two closely related heterocyst-forming cyanobacteria
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 Photochemistry and Molecular Science, Microbial Chemistry.
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 Photochemistry and Molecular Science, Microbial Chemistry. (Karin Stensjö)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
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2015 (English)In: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 362, no 6, article id fnv017Article in journal (Refereed) Published
Abstract [en]

In cyanobacteria, DNA-binding proteins from starved cells (Dps) play an important role in the cellular response to oxidative and nutritional stresses. In this study, we have characterized the cell-type specificity and the promoter regions of two orthologous dps genes, Npun_R5799 in Nostoc punctiforme and alr3808 in Anabaena sp. PCC 7120. A transcriptional start site (TSS), identical in location to the previously identified proximal TSS of alr3808, was identified for Npun_R5799 under both combined nitrogen supplemented and N-2-fixing growth conditions. However, only alr3808 was also transcribed from a second distal TSS. Sequence homologies suggest that the promoter region containing the distal TSS is not conserved upstream of orthologous genes among heterocyst-forming cyanobacteria. The analysis of promoter GFP-reporter strains showed a different role in governing cell-type specificity between the proximal and distal promoter of alr3808. We here confirmed the heterocyst specificity of the distal promoter of alr3808 and described a very early induction of its expression during proheterocyst differentiation. In contrast, the complete promoters of both genes were active in all cells. Even though Npun_R5799 and alr3808 are orthologs, the regulation of their respective expression differs, indicating distinctions in the function of these cyanobacterial Dps proteins depending on the strain and cell type.

Place, publisher, year, edition, pages
2015. Vol. 362, no 6, article id fnv017
Keyword [en]
Cyanobacteria, Nostoc, Anabaena, heterocyst differentiation, ferritin-like protein, ROS scavenging, DIF motif
National Category
Microbiology
Identifiers
URN: urn:nbn:se:uu:diva-258897DOI: 10.1093/femsle/fnv017ISI: 000356885900005OAI: oai:DiVA.org:uu-258897DiVA, id: diva2:842600
Funder
Knut and Alice Wallenberg FoundationCarl Tryggers foundation
Available from: 2015-07-21 Created: 2015-07-21 Last updated: 2018-03-01
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)
Opponent
Supervisors
Available from: 2018-03-26 Created: 2018-03-01 Last updated: 2018-04-24

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Li, XinSandh, GustafMuro-Pastor, Alicia M.Stensjo, Karin

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