Interclonal proteomic responses to predator exposure in Daphnia magna may depend on predator composition of habitats

Abstract

Phenotypic plasticity, the ability of one genotype to express different phenotypes in response to changing environmental conditions, is one of the most common phenomena characterizing the living world and is not only relevant for the ecology but also for the evolution of species. Daphnia, the water flea, is a textbook example for predator-induced phenotypic plastic defences; however, the analysis of molecular mechanisms underlying these inducible defences is still in its early stages. We exposed Daphnia magna to chemical cues of the predator Triops cancriformis to identify key processes underlying plastic defensive trait formation. To get a more comprehensive idea of this phenomenon, we studied four genotypes with five biological replicates each, originating from habitats characterized by different predator composition, ranging from predator-free habitats to habitats containing T. cancriformis. We analysed the morphologies as well as proteomes of predator-exposed and control animals. Three genotypes showed morphological changes when the predator was present. Using a high-throughput proteomics approach, we found 294 proteins which were significantly altered in their abundance after predator exposure in a general or genotype-dependent manner. Proteins connected to genotype-dependent responses were related to the cuticle, protein synthesis and calcium binding, whereas the yolk protein vitellogenin increased in abundance in all genotypes, indicating their involvement in a more general response. Furthermore, genotype-dependent responses at the proteome level were most distinct for the only genotype that shares its habitat with Triops. Altogether, our study provides new insights concerning genotype-dependent and general molecular processes involved in predator-induced phenotypic plasticity in D. magna.

Contrasting gene expression programs correspond with predator‐induced phenotypic plasticity within and across generations in Daphnia

“…Despite a sensible explanation for this observation as being linked to an increase in translation, previous studies have shown increased transcription of ribosomal proteins without increased production of ribosomes (Sun, Li, & Wang, ; Wang et al., ). Proteomic data gathered on D. magna in response to predator cues show similar, but less extreme responses in ribosomal protein up‐regulation (Otte, Schrank, Frohlich, Arnold, & Laforsch, ). Furthermore, it is known that ribosomal proteins have functions outside of ribosome assembly and translation in response to stress (i.e., oncoprotein suppression, immune signalling and development; Zhou, Liao, Liao, Liao, & Lu, ).…”

Bayesian updating during development predicts genotypic differences in plasticity

“…For instance, many organisms express antipredator traits at the beginning of independent life, for example, as hatchlings, neonates, and seedlings (Osborn and Jaffe 1998;Laforsch and Tollrian 2004;Bosak et al 2013;Garla et al 2015). The expression of such traits can vary across genotypes prior to any exposure to cues from predators, and genotypes can differ with respect to the plasticity of those traits in response to cues from predators (Fischer et al 2014b;Sjoqvist et al 2014;Otte et al 2015;Christjani et al 2016). However, when animals are exposed to cues from predators, changes in antipredator behavior typically occur more rapidly than changes in morphological antipredator defenses (Van Buskirk 2002;Hossie and Murray 2012;Orizaola et al 2012).…”

Insights into the genetic basis of predator-induced response inDaphnia galeata

“…Since Daphnia need to shed their rigid carapace in order to grow, molting is directly related to changes in body size. Another analysis of D. magna exposed to Triops cancriformis kairomones revealed the role of proteins related to the cuticle, muscular system, energy metabolism and regulatory proteins that may be involved in morphological carapace defenses and changes in resource allocation (Otte et al 2014). In conclusion, a number of biological functions hypothesized to be involved in kairomone response could be confirmed, e.g., transcripts related to body remodeling and growth.…”

“…The 'structural constituent of cuticle' was enriched in D. pulex exposed to Chaoborus kairomones Rozenberg et al 2015) and related to remodeling of the cuticle. Furthermore, it was also enriched in the proteomic response of D. magna to Triops cancriformis (Otte et al 2015) and is thought to be related to changes in carapace morphology as well as the formation of ultrastructural defenses of the cuticle (Rabus et al 2013). Genes related to body remodeling and activation of cuticle proteins were enriched for D. magna exposed to vertebrate and invertebrate predator kairomones (Orsini et al 2018).…”