Examining the role of DNA methylation in transcriptomic plasticity of early stage sea urchins

Marie Strader1,2, Logan Kozal3, Terence S Leach4, Juliet M Wong5, Jannine D Chamorro6, Madeline J Housh6 and Gretchen Hofmann3, (1)United States, (2)Auburn University, Department of Biological Sciences, Auburn, United States, (3)University of California Santa Barbara, Department of Ecology, Evolution, and Marine Biology, Santa Barbara, CA, United States, (4)Univeristy of California Santa Barbara, Ecology, Evolution and Marine Biology, Santa Barbara, CA, United States, (5)University of California Santa Barbara, Ecology, Evolution and Marine Biology, Santa Barbara, CA, United States, (6)University of California Santa Barbara, Ecology Evolution and Marine Biology, Santa Barbara, CA, United States
Abstract:
Plasticity in gene expression can confer physiological plasticity in response to changes in the abiotic the environment. However, whether epigenetic marks contribute to the dynamics of gene expression is still unknown in most marine invertebrates. Here, we explored the extent and molecular basis of intra- and transgenerational plasticity in the purple sea urchin, Strongylocentrotus purpuratus, by examining relationships between changes in DNA methylation, transcription, and embryo spicule length. Adult urchins were conditioned in the lab for 4 months to treatments that represented upwelling (~1,100μatm pCO2, 13 °C) and non-upwelling conditions (~500μatm pCO2, 17 °C). Embryos spawned from conditioned adults were reared in either the same or the reciprocal adult condition. Maternal conditioning resulted in significantly differentially methylated CpG sites and differential gene expression in the larvae, despite little evidence of maternal effects on spicule length. In contrast, conditions experienced during development resulted in significant differences in larval spicule length. Intragenerational plasticity in spicule length was strongly correlated to transcriptomic plasticity, despite low levels of intragenerational plasticity in CpG methylation. We found plasticity in DNA methylation and gene expression in response to different maternal environments, and these changes had similarities across broad functional groups of genes; yet exhibit little overlap on a gene-by-gene basis. Our results suggest that different forms of environmentally induced plasticity are observable across different time scales, and that DNA methylation dynamics may be uncoupled from fast transcriptional responses to the environment and whole organism traits. Overall, this study illuminates the extent to which environmental variability can induce both intra- and transgenerational phenotypic plasticity in a benthic marine invertebrate that experiences a dynamic environment in the kelp forest.
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