Understanding how changes in developmental gene expression alter morphogenesis is a fundamental problem in development and evolution. A promising approach to address this problem is to compare the developmental transcriptomes between related species. The echinoderm phylum consists of several model species that have significantly contributed to the understanding of gene regulation and evolution. Particularly, the regulatory networks of the sea star, Patiria miniata (P. miniata), have been extensively studied, however developmental transcriptomes for this species were lacking. Here we generated developmental transcriptomes of P. miniata and compared these with those of two sea urchins species. We demonstrate that the conservation of gene expression depends on gene function, cell type and evolutionary distance. With increasing evolutionary distance the interspecies correlations in gene expression decreases. The reduction is more severe in the correlations between morphologically equivalent stages (diagonal elements) than in the correlation between morphologically distinct stages (off-diagonal elements). This could reflect a decrease in the morphological constraints compared to other constraints that shape gene expression at large evolutionary divergence. Within this trend, the interspecies correlations of developmental control genes maintain their diagonality at large evolutionary distance, and peak at the onset of gastrulation, supporting the hourglass model of phylotypic stage conservation.
Bibliographical noteFunding Information:
We thank Assaf Malik from the bioinformatics service unit at the University of Haifa for the analyses of the transcriptome data. We thank the Genomics unit at the Grand Israel National Center for Personalized Medicine (G-INCPM) for their assistance with library preparation and sequencing. We thank Paola Oliveri for the idea to study specific cell populations. This work was supported by the Binational Science Foundation Grant Number 2015031 to S.B.D. and V.F.H. and the Israel Science Foundation Grants Number 2304/15 (ISF-INCPM) and 41/14 (I.S.F.) to S.B.D., the National Science Foundation grants IOS 1557431 and MCB 1715721 to VFH and the National Institute of Health grant P41HD071837 to V.F.H.
© 2019, The Author(s).
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