Journal Article

Overexpression of FurA in <i>Anabaena</i> sp. PCC 7120 Reveals New Targets for This Regulator Involved in Photosynthesis, Iron Uptake and Cellular Morphology

Andrés González, M. Teresa Bes, François Barja, M. Luisa Peleato and María F. Fillat

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 51, issue 11, pages 1900-1914
Published in print November 2010 | ISSN: 0032-0781
Published online October 2010 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcq148
Overexpression of FurA in Anabaena sp. PCC 7120 Reveals New Targets for This Regulator Involved in Photosynthesis, Iron Uptake and Cellular Morphology

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  • Molecular and Cell Biology
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Previous genomic analyses of the filamentous nitrogen-fixing cyanobacterium Anabaena sp. PCC 7120 have identified three ferric uptake regulator (Fur) homologs with low sequence identities and probably different functions in the cell. FurA is a constitutive protein that shares the highest homology with Fur from heterotrophic bacteria and appears to be essential for in vitro growth. In this study, we have analysed the effects of FurA overexpression on the Anabaena sp. phenotype and investigated which of the observed alterations were directly operated by FurA. Overexpression of the regulator led to changes in cellular morphology, resulting in shorter filaments with rounded cells of different sizes. The furA-overexpressing strain showed a slower photoautotrophic growth and a marked decrease in the oxygen evolution rate. Overexpression of the regulator also decreased both catalase and superoxide dismutase activities, but did not lead to an increase in the levels of intracellular reactive oxygen species. By combining phenotypic studies, reverse transcription–PCR analyses and electrophoretic mobility shift assays, we identified three novel direct targets of FurA, including genes encoding a siderophore outer membrane transporter (schT), bacterial actins (mreBCD) and the PSII reaction center protein D1 (psbA). The affinity of FurA for these novel targets was markedly affected by the absence of divalent metal ions, confirming previous evidence of a critical role for the metal co-repressor in the function of the regulator in vivo. The results unravel new cellular processes modulated by FurA, supporting its role as a global transcriptional regulator in Anabaena sp. PCC 7120.

Keywords: Anabaena; Ferric uptake regulator; Growth; Morphology; Oxidative stress defenses; Photosynthesis

Journal Article.  8269 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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