Transcriptomics-Aided Dissection of the Intracellular and Extracellular Roles of Microcystin in Microcystis aeruginosa PCC 7806

A. Katharina Makower, J. Merijn Schuurmans, Detlef Groth, Yvonne Zilliges, Hans C. P. Matthijs, Elke Dittmann

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Recent studies have provided evidence for both intracellular and extracellular roles of the potent hepatotoxin microcystin (MC)
in the bloom-forming cyanobacterium Microcystis. Here, we surveyed transcriptomes of the wild-type strain M. aeruginosa PCC
7806 and the microcystin-deficient mcyB mutant under low light conditions with and without the addition of external MC of
the LR variant (MC-LR). Transcriptomic data acquired by microarray and quantitative PCR revealed substantial differences
in the relative expression of genes of the central intermediary metabolism, photosynthesis, and energy metabolism. In particular,
the data provide evidence for a lower photosystem I (PSI)-to-photosystem II (PSII) ratio and a more pronounced carbon
limitation in the microcystin-deficient mutant. Interestingly, only 6% of the transcriptional differences could be complemented
by external microcystin-LR addition. This MC signaling effect was seen exclusively for genes of the secondary metabolism category.
The orphan polyketide synthase gene cluster IPF38-51 was specifically downregulated in response to external MC-LR under
low light. Our data suggest a hierarchical and light-dependent cross talk of secondary metabolites and support both an intracellular
and an extracellular role of MC in Microcystis.
Original languageEnglish
Pages (from-to)544-554
JournalApplied and Environmental Microbiology
Issue number2
Publication statusPublished - 2015


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