Wild Dictyostelium discoideum social amoebae show plastic responses to the presence of nonrelatives during multicellular development

Abstract

When multiple strains of microbes form social groups, such as the multicellular fruiting bodies of Dictyostelium discoideum, conflict can arise regarding cell fate. Both fixed and plastic differences among strains can contribute to cell fate, and plastic responses may be particularly important if social environments frequently change. We used RNA‐sequencing and photographic time series analysis to detect possible conflict‐induced plastic differences between wild D. discoideum aggregates formed by single strains compared with mixed pairs of strains (chimeras). We found one hundred and two differentially expressed genes that were enriched for biological processes including cytoskeleton organization and cyclic AMP response (up‐regulated in chimeras), and DNA replication and cell cycle (down‐regulated in chimeras). In addition, our data indicate that in reference to a time series of multicellular development in the laboratory strain AX4, chimeras may be slightly behind clonal aggregates in their development. Finally, phenotypic analysis supported slower splitting of aggregates and a nonsignificant trend for larger group sizes in chimeras. The transcriptomic comparison and phenotypic analyses support discoordination among aggregate group members due to social conflict. These results are consistent with previously observed factors that affect cell fate decision in D. discoideum and provide evidence for plasticity in cAMP signaling and phenotypic coordination during development in response to social conflict in D. discoideum and similar microbial social groups.

Social selection within aggregative multicellular development drives morphological evolution

“…Social forces such as cooperation, cheating and interference competition have the potential to influence developmental processes and their evolutionary trajectories [ 9 , 13 , 14 ]. In aggregative developmental systems, such social forces occur within the developmental process because conspecifics are the cells that carry out development.…”

Hidden paths to endless forms most wonderful: Ecology latently shapes evolution of multicellular development in predatory bacteria

“…S2). Consistently in all assays, 50 µl of resuspended culture (∼2.5 x 10 8 cells) were spotted at the center of TPM agar plates and incubated at 32 °C for 5 days before the plates were imaged and morphological traits subsequently quantified.…”

“…A total of ∼2.5 x 10 8 cells in a 50 ul suspension (TPM liquid) were spotted on each starvation plate (TPM 1.5% agar) and harvested after 5 days using a sterile spatula and washed into one milliliter of ddH 2 O. Samples were then heated at 50 °C for 2 hours to kill vegetative cells, sonicated, diluted into CTT soft agar and incubated for 7 days before colonies were counted.…”

“…A recently-emerged focus on eco-evo-devo seeks to quantitatively understand such ecological causation of developmental evolution 3,4 . Many biotic ecological factors, such as predator-prey [5][6][7] and social interactions [8][9][10] , as well as abiotic factors such as temperature [11][12][13] and oxygen level [14][15][16] are hypothesized or known to play important roles in shaping the evolution of developmental features 4,17 , including developmental plasticity [18][19][20][21][22][23][24] .…”

Social selection within aggregative multicellular development drives morphological evolution

“…Biotic selection shaping development occurs both across and within species, for example from predation (2,8) and sexual selection (9,10), respectively. Other social forces such as interference competition and cheating also have potential to shape the evolution of developmental systems but are less studied in this regard (9,(11)(12)(13)(14). Developmental-system evolution might be shaped not only by external selective forces, but also by internal system features (4-7).…”