Evolutionary Constraints
Posted in Evolution on December 21st, 2008 by BradfordDevelopmental Constraints on Vertebrate Genome Evolution by Julien Roux and Marc Robinson-Rechavi is a PLOS Genetics paper. The authors explore how embryonic developmental processes constrain genomic evolution. They note that it has been known for some time that developmental timing is linked to morphological divergence but molecular explanations have been found wanting due to insufficient understanding. The ratio of non-synonymous to synonymous substitutions (dN/dS) in protein coding genes, has been used to measure selective pressure. But scant is robust evidence at early developmental stages for a lower dN/dS ratio.
The authors generated gene expression data from mice and zebrafish from multiple stages of development supporting the notion of high constraints in early stages of vertebrate development. They found that a pattern of constraints differed from an hourglass model used to describe vertebrate morphological conservation. The difference being that morphological constraints were maximized at mid-development while genomic constraints continuously decrease over developmental time. Quoting from the summary:


