TY - JOUR T1 - Developmental constraints on genome evolution in four bilaterian model species JF - bioRxiv DO - 10.1101/161679 SP - 161679 AU - Jialin Liu AU - Marc Robinson-Rechavi Y1 - 2017/01/01 UR - http://biorxiv.org/content/early/2017/11/14/161679.abstract N2 - Developmental constraints on genome evolution have been suggested to follow either an early conservation model or an “hourglass” model. Both models agree that late development strongly diverges between species, but debate on which developmental period is the most conserved. Here, based on a modified “Transcriptome Age Index” approach, i.e. weighting parameters by expression level, we analyzed the constraints acting on three evolutionary traits of protein coding genes (strength of purifying selection on protein sequences, phyletic age, and duplicability) in four species: nematode worm C. elegans, fly D. melanogaster, zebrafish D. rerio and mouse M. musculus. In general, we found that both models can be supported by different genomic properties. The evolution of phyletic age and of duplicability follow an early conservation model in all species, but sequence evolution follows different models in different species: an early conservation model in fly, and an hourglass model in both zebrafish and mouse. Further analyses indicate that stronger purifying selection on sequences in early development of fly and during the morphological ‘phylotypic’ period of zebrafish and mouse are driven by temporal pleiotropy of these genes. In addition, we report evidence that expression in late development is enriched with retrogenes, which usually lack efficient regulatory elements. This implies that expression in late development could facilitate transcription of new genes, and provide opportunities for acquisition of function. Finally, in nematode, we suggest that dosage imbalance could be one of the main factors that cause depleted expression of high duplicability genes in early development. ER -