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Diazocyte differentiation is induced upon combined nitrogen deprivation in the marine cyanobacterium Trichodesmium erythraeum IMS101
Stockholm University, Faculty of Science, Department of Botany.
Stockholm University, Faculty of Science, Department of Botany.
Stockholm University, Faculty of Science, Department of Botany.
(English)Manuscript (Other academic)
Keyword [en]
Trichodesmium, cyanobacteria, diazocyte, nitrogen fixation, cell differentiation
National Category
Botany
Research subject
Plant Physiology
Identifiers
URN: urn:nbn:se:su:diva-27221OAI: oai:DiVA.org:su-27221DiVA: diva2:212969
Available from: 2009-04-26 Created: 2009-04-26 Last updated: 2010-01-14Bibliographically approved
In thesis
1. Towards an understanding of diazocyte development and diazotrophy in the marine cyanobacterium Trichodesmium
Open this publication in new window or tab >>Towards an understanding of diazocyte development and diazotrophy in the marine cyanobacterium Trichodesmium
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Trichodesmium is a filamentous cyanobacterium of great ecological significance as it contributes significantly to primary production in oceans through an efficient nitrogen fixation strategy, including a unique cell type, the diazocyte. The aim of this thesis was to generate a deeper understanding of the structural and molecular background related to the development of diazocytes and the maintenance of diazotrophy in Trichodesmium erythraeum IMS101.

Data obtained demonstrated a diurnal separation of basic physiological processes, with nitrogen fixation and photosynthesis confined to the light and cell division and diazocyte development to the dark period. Diazocyte development was preceded by cell division and expression of the main regulator of heterocyst differentiation, hetR. In non-diazotrophic cultures, subject to nitrogen depletion, a developmental program was initiated in a subset of cells that differentiated into mature nitrogenase containing diazocytes, while addition of combined nitrogen abolished development. A nitrogen depletion signal initially enhanced transcription of the global nitrogen regulator ntcA and was followed by elevated expression of coxBII (respiration) and glnA (primary ammonia assimilation) and pronounced sub-cellular rearrangements. Comparative proteomic analysis further revealed a clear shift in the cellular metabolism depending on the nitrogen regime, with 94 proteins being differentially expressed in diazotrophic (with diazocytes) as opposed to in non-diazotrophic cultures. Proteins up-shifted in diazotrophic cultures were related to supporting the nitrogenase enzyme with reducing equivalents and a lower oxygen tension. In addition, two highly divergent flavodoxins were identified with different expression patterns in response to combined nitrogen additions and the data discourage the use of flavodoxins as indicators of iron stress in Trichodesmium populations.

 

Place, publisher, year, edition, pages
Stockholm: Department of Botany, Stockholm University, 2009. 51 p.
Keyword
Cyanobacteria, Trichodesmium, diazocyte, cell differentiation, nitrogen fixation, cell division, flavodoxin
National Category
Botany
Research subject
Plant Physiology
Identifiers
urn:nbn:se:su:diva-27206 (URN)978-91-7155-885-5 (ISBN)
Public defence
2009-05-29, Föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2009-05-08 Created: 2009-04-24 Last updated: 2009-05-07Bibliographically approved

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