Biochemical and growth performance of the aquatic macrophyte Azolla filiculoides to sub-chronic exposure to cylindrospermopsin

Abstract

Physiological and biochemical effects of cylindrospermopsin (CYN), a cyanobacterial toxin that inhibits protein synthesis and released during a harmful cyanobacterial bloom, has been overlooked in plants. Therefore, at the present research, the toxic effects (physiological and biochemical) of a crude extract containing CYN were assessed in the aquatic fern Azolla filiculoides exposed to three concentrations (0.05, 0.5 and 5 μg CYN mL(-1)). At 5 μg CYN mL(-1), fern growth rate has showed a drastic decrease (0.001 g g(-1) day(-1)) corresponding to a 99.8% inhibition, but at the concentrations of 0.05 and 0.5 μg CYN mL(-1) the growth rate was similar to the control plants. Growth rate also indicated a IC50 of 2.9 μg CYN mL(-1). Those data point to the presence of other compounds in the crude extract may stimulate the fern growth and/or the fern is tolerant to CYN. Chlorophyll (a and b), carotenoids and protein content as well as the activities of glutathione reductase (GR) and glutathione-S-transferase (GST) has increased at 5 μg CYN mL(-1) which may indicate that photosynthesis and protein synthesis are not affected by CYN and the probable activation of defense and detoxifying mechanisms to overcome the effects induced by the presence of CYN. Low uptake of cylindrospermopsin (1.314 μg CYN g(-1) FW) and low bioconcentration factor (0.401) point towards to a safe use of A. filiculoides as biofertilizer and as food source, but also indicate that the fern is not suitable for CYN phytoremediation.

Validation of a Method for Cylindrospermopsin Determination in Vegetables: Application to Real Samples Such as Lettuce (Lactuca sativa L.)

“…However, in spite of the human health risks associated with CYN, less attention has been given to its bioaccumulation in edible agricultural plants compared with MCs [ 37 ], which is considered a public health concern, given CYN's high water-solubility and its ability to transfer to higher trophic levels [ 38 ]. This bioaccumulation may be possible because of the absorption of toxins by plants if surface water contaminated with cyanotoxins is used in agriculture, thus posing risks for food safety.…”

The Individual and Combined Effects of the Cyanotoxins, Anatoxin-a and Microcystin-LR, on the Growth, Toxin Production, and Nitrogen Fixation of Prokaryotic and Eukaryotic Algae

“…Given the increased activity of the enzyme, GST, in strains of Microcystis , it is seems likely involved in the detoxification of ATX and MC-LR. Several studies have shown that GST is actively involved in the detoxification and biotransformation of cyanotoxins into molecules that are less toxic to the cell [11,14,16,17,18,26,51]. The detoxification and biotransformation of cyanotoxins in cells is carried out via a conjugation process that is catalyzed by GST using the reduced form of glutathione [52,53].…”

The Unique Symbiotic System between a Fern and a Cyanobacterium, Azolla-Anabaena azollae: Their Potential as Biofertilizer, Feed, and Remediation

“…Some authors hypothesize that the A. filiculoides could uptake and remove those cyanotoxins from the water. However, the fern did not uptake nor accumulate microcystins [81] and cylindrospermopsin [82], making this fern not suitable to the phytoremediation of those environmental contaminants.…”