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- Popova, Alexandra A., et al.
(författare)
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Stress effects of cyanotoxin beta-methylamino-L-alanine (BMAA) on cyanobacterial heterocyst formation and functionality
- 2018
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Ingår i: Environmental Microbiology Reports. - : Wiley. - 1758-2229. ; 10:3, s. 369-377
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Tidskriftsartikel (refereegranskat)abstract
- Various species of cyanobacteria, diatoms and dinoflagellates are capable of synthesizing the non-proteinogenic neurotoxic amino acid -N-methylamino-L-alanine (BMAA), which is known to be a causative agent of human neurodegeneration. Similar to most cyanotoxins, the biological and ecological functions of BMAA in cyanobacteria are unknown. In this study, we show for the first time that BMAA, in micromolar amounts, inhibits the formation of heterocysts (specialized nitrogen-fixing cells) in heterocystous, diazotrophic cyanobacteria [Anabaena sp. PCC 7120, Nostoc punctiforme PCC 73102 (ATCC 29133), Nostoc sp. strain 8963] under conditions of nitrogen starvation. The inhibitory effect of BMAA is abolished by the addition of glutamate. To understand thegenetic reason for the observed phenomenon, we used qPCR to study the expression of key genes involved in celldifferentiation and nitrogen metabolism in the model cyanobacterium Anabaena sp. PCC 7120. We observed that in the presence of BMAA, Anabaena sp. PCC 7120 does not express two essential genes associated with heterocyst differentiation, namely, hetR and hepA. We also found that addition of BMAA to cyanobacterial cultures with mature heterocysts inhibits nifH gene expression and nitrogenase activity.
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| 2. |
- Popova, Alexandra A., et al.
(författare)
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The Cyanotoxin BMAA Induces Heterocyst Specific Gene Expression in Anabaena sp PCC 7120 under Repressive Conditions
- 2018
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Ingår i: Toxins. - : MDPI AG. - 2072-6651. ; 10:11
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Tidskriftsartikel (refereegranskat)abstract
- Cyanobacteria synthesize neurotoxic -N-methylamino-l-alanine (BMAA). The roles of this non-protein amino acid in cyanobacterial cells are insufficiently studied. During diazotrophic growth, filamentous cyanobacteria form single differentiated cells, called heterocysts, which are separated by approximately 12-15 vegetative cells. When combined nitrogen is available, heterocyst formation is blocked and cyanobacterial filaments contain only vegetative cells. In the present study, we discovered that exogenous BMAA induces the process of heterocyst formation in filamentous cyanobacteria under nitrogen-replete conditions that normally repress cell differentiation. BMAA treated cyanobacteria form heterocyst-like dark non-fluorescent non-functional cells. It was found that glutamate eliminates the BMAA mediated derepression. Quantitative polymerase chain reaction (qPCR) permitted to detect the BMAA impact on the transcriptional activity of several genes that are implicated in nitrogen assimilation and heterocyst formation in Anabaena sp. PCC 7120. We demonstrated that the expression of several essential genes increases in the BMAA presence under repressive conditions.
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