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Microcystin-LR synthesis as response to nitrogen: transcriptional analysis of the mcyD gene in Microcystis aeruginosa PCC7806

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Abstract

The influence of environmental factors on microcystin production by toxic cyanobacteria has been extensively studied. However, the effect of nitrogen on the synthesis of this toxin remains unclear because of the literature contradictory data. The aim of this work was to determine how nitrate affects the transcriptional response of mcyD gene and the microcystin-LR synthesis in Microcystis aeruginosa PCC 7806. For first time real time RT-PCR has been used to investigate the effect of nitrogen availability. Our results show that, under laboratory conditions, an excess of nitrate triggers Microcystis aeruginosa growth without increasing the synthesis of microcystin-LR per cell. The concentration of microcystin in the cultures correlates with mcyD gene expression, being both parameters independent of nitrate availability. Analysis of the bidirectional promoter mcy unravels that the transcription start points of mcyA and mcyD genes did not change under different nitrate regimes. The effect of nitrate inputs in the development of toxic blooms is primarily due to the increased growth rate and population, not to the induction of the mcy operon.

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Acknowledgements

This work was funded by the Spanish Ministerio de Educación y Ciencia (BFU2006-03454). Laura Vela and Emma Sevilla were partially supported by a fellowship from the BIFI (Zaragoza, Spain). Beatriz Martin was recipient of a Gobierno de Aragón fellowship.

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  1. Departamento de Bioquimica y Biologia Molecular y Celular, Facultad de Ciencias, and BIFI, Universidad de Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain

    Emma Sevilla, Beatriz Martin-Luna, Laura Vela, M. Teresa Bes, M. Luisa Peleato & Maria F. Fillat

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  1. Emma Sevilla
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  2. Beatriz Martin-Luna
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  3. Laura Vela
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  4. M. Teresa Bes
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  5. M. Luisa Peleato
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  6. Maria F. Fillat
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Correspondence to M. Luisa Peleato.

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Sevilla, E., Martin-Luna, B., Vela, L. et al. Microcystin-LR synthesis as response to nitrogen: transcriptional analysis of the mcyD gene in Microcystis aeruginosa PCC7806. Ecotoxicology 19, 1167–1173 (2010). https://doi.org/10.1007/s10646-010-0500-5

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