WIKIMEDIA COMMONS/JAVIER MARTIN
EDITOR'S CHOICE IN GENETICS & GENOMICS
J.J. Herman, S.E. Sultan, “DNA methylation mediates genetic variation for adaptive transgenerational plasticity,” Proc R Soc B, doi:10.1098/rspb.2016.0988, 2016.
The notion that organisms pass down adaptations acquired during their lifetimes to their offspring was overturned long ago by Darwinian evolution. But the concept is getting a second chance, with more nuance. Growing evidence shows that a parent’s environment sometimes does influence offspring, though the underlying process is something of a black box.
Growing up Hard
Sonia Sultan and Jacob Herman of Wesleyan University in Middletown, Connecticut, peeked into that box with experiments on a small flowering annual, Polygonum persicaria. They grew some plants in dry soil and other plants in normal soil, then raised offspring from all plants in dry soil. In some members of the progeny, they disrupted 15 percent to 20 percent of DNA methylation—a means of epigenetic regulation—across the genome.
Plants whose parents endured drought were better prepared to face the same hardship, growing larger as seedlings, setting down deeper roots, and making broader leaves. But in demethylated plants, that effect went away, lending evidence to the idea that epigenetics had a role in this form of adaptation.
Adjusting offspring traits to better suit the parental environment is itself an evolved trait, notes Julie Etterson, an evolutionary ecologist at the University of Minnesota Duluth who was not involved in the research. The authors used plants from 12 genetically distinct populations and not all of them showed the transgenerational effect, raising questions about when and why this trait is advantageous. Sultan says these environmental hand-me-downs are a phenomenon “not accounted for by standard models of evolution.”