TITLE:
Dynamics of Cylindrospermopsin Production and Toxin Gene Expression in Aphanizomenon ovalisporum
AUTHORS:
Ángel Barón-Sola, Francisca F. del Campo, Soledad Sanz-Alférez
KEYWORDS:
Cyanobacteria, Cyanotoxins, aoa Genes, cyrGenes, ntcA Gene, Gene Regulation
JOURNAL NAME:
Advances in Microbiology,
Vol.6 No.5,
April
27,
2016
ABSTRACT: Aphanizomenon ovalisporum is a cylindrospermopsin (CYN)-producing cyanobacteria species that
due to its increasing worldwide distribution has become an important health alarm in the last few
years. Several clusters of genes involved in CYN production have been described in different CYN+
cyanobacteria genera, named aoa for Aphanizomenon and cyr for Cylindrospermopsis and others
strains. The sequences of those genes are highly similar, but a rearrangement in gene order is also
observed. The information on the control of CYN production by gene expression is still scarce, especially
in Aphanizomenon. To obtain further information about the control of CYN production in A.
ovalisporum, we have quantified the intra and extracellular CYN content, during nine days in BG11
batch cultures under optimal conditions. In parallel, the expression of four genes related to CYN
synthesis, aoaA-C and cyrJ, has been analyzed by real time q-PCR. The results show a similar pattern
of total CYN accumulation and gene expression. Most of the CYN is found intracellularly. Considering
the high nitrogen content in the CYN molecule, we have explored if nitrogen assimilation
could be related to CYN synthesis. We found inside the aoaA and aoaC sequences several putative
binding domains for the global nitrogen regulator NtcA. The pattern of the ntcA expression along
the culture is similar to that of CYN accumulation. Our data suggest that CYN production in A. ovalisporum
seems to be controlled both by the expression of genesaoa and ntcA, this last one suggesting
the influence of available nitrogen; however, other regulation mechanisms of CYN synthesis
cannot be discarded.