Identification of pathways, gene networks, and paralogous gene families in Daphnia pulex responding to exposure to the toxic cyanobacterium Microcystis aeruginosa.
Although cyanobacteria produce a wide range of natural toxins that impact aquatic organisms, food webs, and water quality, the mechanisms of toxicity are still insufficiently understood. Here, we implemented a whole-genome expression microarray to identify pathways, gene networks, and paralogous gene families responsive to  Microcystis  stress in  Daphnia pulex . Therefore, neonates of a sensitive isolate were given a diet contaminated with  Microcystis  to contrast with those given a control diet for 16 days. The microarray revealed 2247 differentially expressed (DE) genes (7.6% of the array) in response to  Microcystis , of which 17% are lineage-specific (i.e., these genes have no detectable homology to any other gene in currently available databases) and 49% are gene duplicates (paralogues). We identified four pathways/gene networks and eight paralogous gene families affected by  Microcystis . Differential regulation of the ribosome, including three paralogous gene families encoding 40S, 60S, and mitochondrial ribosomal proteins, suggests an impact of  Microcystis  on protein synthesis of  D. pulex . In addition, differential regulation of the oxidative phosphorylation pathway (including the NADH:ubquinone oxidoreductase gene family) and the trypsin paralogous gene family (a major component of the digestive system in  D. pulex ) could explain why fitness is reduced based on energy budget considerations.
Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University, Ghent, Belgium. jana.asselman@ugent.be
Jana
J
Asselman
Dieter I M
DI
De Coninck
Stephen
S
Glaholt
John K
JK
Colbourne
Colin R
CR
Janssen
Joseph R
JR
Shaw
Karel A C
KA
De Schamphelaere
D000818:Animals; D003621:Daphnia / Q000235:genetics*; D053263:Gene Regulatory Networks; D046931:Microcystis / Q000472:pathogenicity*; D005810:Multigene Family; D060888:Real-Time Polymerase Chain Reaction