| Title: | Ecophysiological Aspects and sxt Genes Expression Underlying Induced Chemical Defense in STX-Producing Raphidiopsis raciborskii (Cyanobacteria) against the Zooplankter Daphnia gessneri |
| Author(s): | Vilar MCP; Rodrigues T; Silva LO; Pacheco ABF; Ferrao-Filho AS; Azevedo S; |
| Address: | "Laboratory Ecophysiology and Toxicology of Cyanobacteria, Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro 21949-902, Brazil. Laboratory Biological Physics, Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro 21949-902, Brazil. Laboratory of Evaluation and Promotion of Environmental Health, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro 21040-360, Brazil" |
| ISSN/ISBN: | 2072-6651 (Electronic) 2072-6651 (Linking) |
| Abstract: | "Cyanobacteria stand out among phytoplankton when they form massive blooms and produce toxins. Because cyanotoxin genes date to the origin of metazoans, the hypothesis that cyanotoxins function as a defense against herbivory is still debated. Although their primary cellular function might vary, these metabolites could have evolved as an anti-predator response. Here we evaluated the physiological and molecular responses of a saxitoxin-producing Raphidiopsis raciborskii to infochemicals released by the grazer Daphnia gessneri. Induced chemical defenses were evidenced in R. raciborskii as a significant increase in the transcription level of sxt genes, followed by an increase in saxitoxin content when exposed to predator cues. Moreover, cyanobacterial growth decreased, and no significant effects on photosynthesis or morphology were observed. Overall, the induced defense response was accompanied by a trade-off between toxin production and growth. These results shed light on the mechanisms underlying zooplankton-cyanobacteria interactions in aquatic food webs. The widespread occurrence of the cyanobacterium R. raciborskii in freshwater bodies has been attributed to its phenotypic plasticity. Assessing the potential of this species to thrive over interaction filters such as zooplankton grazing pressure can enhance our understanding of its adaptive success" |
| Keywords: | "Animals *Cylindrospermopsis/genetics/growth & development/metabolism Daphnia/*metabolism Food Chain Gene Expression Regulation, Bacterial Genes, Bacterial Pheromones/*metabolism *Saxitoxin/biosynthesis/genetics Zooplankton/*metabolism cyanotoxins infochem;" |
| Notes: | "MedlineVilar, Mauro C P Rodrigues, Thiago F C P Silva, Luan O Pacheco, Ana Beatriz F Ferrao-Filho, Aloysio S Azevedo, Sandra M F O eng 306174/2018-9/Conselho Nacional de Desenvolvimento Cientifico e Tecnologico/ E-26/203.032/2015/Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro/ Research Support, Non-U.S. Gov't Switzerland 2021/07/03 Toxins (Basel). 2021 Jun 8; 13(6):406. doi: 10.3390/toxins13060406" |
