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Natural Product Discovery with LC-MS/MS Diagnostic Fragmentation Filtering: Application for Microcystin Analysis
Published on: May 31, 2019
Infochemicals released by Daphnia magna fed on Microcystis aeruginosa affect mcyA gene expression
Rosa María Pineda-Mendoza1, Gerardo Zúñiga2, Fernando Martínez-Jerónimo3
1Laboratorio de Hidrobiología Experimental, Departamento de Zoología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Prol. Carpio esq. Plan de Ayala s/n, Col. Sto. Tomás, Mexico, D.F. 11340, Mexico; Laboratorio de Variación Biológica y Evolución, Departamento de Zoología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Prol. Carpio esq. Plan de Ayala s/n, Col. Sto. Tomás, Mexico, D.F. 11340, Mexico.
Abstract:
Microcystins (MCs) are toxic heptapeptides produced by cyanobacteria during blooms that are noxious to diverse organisms, from bacteria to vertebrates. Specifically in daphnids, they cause reduced growth, a low reproductive rate, and, in extreme cases, death; however, different infochemicals released by cladocerans stimulate MCs synthesis. Ecological cyanobacteria-daphnids interactions are complex and not clear yet. In this study, we evaluated the effects of infochemicals released by Daphnia magna neonates and adults fed with different concentrations of Microcystis aeruginosa on population growth of strains Ch10 and UTEX LB2385 of M. aeruginosa, mcyA gene expression in real time qPCR, and the intracellular concentration of MCs. In addition, we assessed the relation between the cellular diameter and the intracellular concentration of MCs in both strains. Chlorophyll content per cell was affected by the presence of infochemicals from D. magna neonates and adults. mcyA gene was significantly overexpressed in the early stages of population growth (5 days) in all treatments with strain UTEX LB2385, whereas overexpression was observed in strain Ch10 at the end stage of the exponential and stationary phases (10 and 15 days). Intracellular concentration of MCs varied with the tested factor. Results suggest that the increase in mcyA gene expression and in MCs production could be defense mechanisms against the consumption by D. magna. Results also demonstrate the physiological plasticity among Microcystis strains, which could explain the permanence and dominance of this genus in toxic blooms.
Insights
Cyanobacteria produce microcystins (MCs) toxic to aquatic life. Daphnia magna infochemicals can trigger MCs synthesis and mcyA gene expression, suggesting a defense mechanism against predation.
Area of Science:
- Environmental Microbiology
- Aquatic Ecology
- Ecotoxicology
Background:
- Microcystins (MCs) are cyanobacterial toxins harmful to aquatic organisms.
- Daphnia magna grazing can influence cyanobacterial toxin production.
- The complex interactions between cyanobacteria and daphnids are not fully understood.
Purpose of the Study:
- To investigate the impact of Daphnia magna infochemicals on Microcystis aeruginosa population growth.
- To analyze mcyA gene expression and intracellular MCs concentration in response to daphnid cues.
- To explore the relationship between cellular diameter and MCs concentration in Microcystis.
Main Methods:
- Exposure of Microcystis aeruginosa strains (Ch10, UTEX LB2385) to infochemicals from Daphnia magna neonates and adults.
- Real-time qPCR for mcyA gene expression analysis.
- Quantification of intracellular microcystins.
- Measurement of cellular diameter and chlorophyll content.
Main Results:
- Daphnia magna infochemicals affected chlorophyll content per cell.
- mcyA gene was significantly overexpressed in Microcystis strains at different growth stages.
- Intracellular MCs concentration varied based on the tested factors.
- A potential link between increased mcyA expression, MCs production, and daphnid presence was observed.
Conclusions:
- Increased mcyA gene expression and MCs production may serve as a defense strategy for Microcystis against Daphnia predation.
- Physiological plasticity among Microcystis strains contributes to their persistence in toxic blooms.
- Understanding these interactions is crucial for managing harmful algal blooms.
