Intrinsically embedded inertial force in phenotypic evolution?
by Naoki Irie | Yui Uchida | Masahiro Uesaka | Haiyang Hu | Philipp Khaitovich | Guojie Zhang | Wen Wang | Jr-Kai Yu | Shigeru Kuratani | Research Center for Integrative Evolutionary Science, SOKENDAI, JAPAN | RIKEN BDR, Japan | Tohoku Univ., Japan | China Pharmaceutical University | Skoltech, Russia | Zhejiang University, China | Kunming Institute of Zoology, China | Institute of Cellular and Organismic Biology, Academia Sinica, Taiwan | RIKEN, Japan
Abstract ID: 94
Event: The 3rd AsiaEvo Conference
Topic: Evolvability: a common currency of evolution, ecology and development
Presenter Name: Naoki Irie

What makes certain phenotypes, such as the basic anatomical patterns of animals (body plans), remain strictly conserved even after hundreds of millions of years of evolution? Potential explanations include purifying selection, the influence of genetic drift, or merely the result of coincidence. In the meantime, I would like to discuss the contribution of less evolvability, which results from having less potential to generate phenotypic variation within a generation.

We initially discovered that the body plan development phase, known as the phylotypic period, is rather robust against mutations and environmental perturbations. This suggests that the conservation of the body plan cannot be solely attributed to the higher lethality of the phylotypic period. Subsequently, we conducted comparative transcriptomic analyses of chordate embryos and found that the phylotypic period is enriched with genes expressed in various stages and tissues. This implies that pleiotropic gene expression itself could contribute to the conservation of the phylotypic period and, by extension, the body plan. While the reuse of existing genes has long been known to facilitate evolutionary diversification (e.g., by creating novel traits), our findings suggest that gene re-utilization has a double-edged sword effect on evolution, limiting diversification.

Finally, the phylotypic period exhibited smaller inter-individual variations than the early and later developmental stages. These results suggest that the period responsible for establishing the body plan has a reduced potential to generate phenotypic variations, making it less likely to diversify even under the pressures of positive selections. In other words, these intrinsic factors could have played a role in contributing to the conservation of strictly conserved features, such as the body plan.