# Molecular basis of canalization in an ascidian species complex adapted to different thermal conditions

## TL;DR

This study explores how certain marine animals maintain consistent traits despite environmental changes, revealing a new role for specific cellular proteins.

## Contribution

The study identifies endoplasmic reticulum chaperones, not heat shock proteins, as key to developmental buffering in natural populations.

## Key findings

- Levels of developmental buffering are maternally inherited in Ciona intestinalis.
- ER chaperone gene expression correlates with buffering levels, unlike canonical Hsp70 and Hsp90.
- ER chaperones are conserved across animal species and may form a cellular basis for canalization.

## Abstract

Canalization is a result of intrinsic developmental buffering that ensures phenotypic robustness under genetic variation and environmental perturbation. As a consequence, animal phenotypes are remarkably consistent within a species under a wide range of conditions, a property that seems contradictory to evolutionary change. Study of laboratory model species has uncovered several possible canalization mechanisms, however, we still do not understand how the level of buffering is controlled in natural populations. We exploit wild populations of the marine chordate Ciona intestinalis to show that levels of buffering are maternally inherited. Comparative transcriptomics show expression levels of genes encoding canonical chaperones such as Hsp70 and Hsp90 do not correlate with buffering. However the expression of genes encoding endoplasmic reticulum (ER) chaperones does correlate. We also show that ER chaperone genes are widely conserved amongst animals. Contrary to previous beliefs that expression level of Heat Shock Proteins (HSPs) can be used as a measurement of buffering levels, we propose that ER associated chaperones comprise a cellular basis for canalization. ER chaperones have been neglected by the fields of development, evolution and ecology, but their study will enhance understanding of both our evolutionary past and the impact of global environmental change.