Evolution of viviparity: Genomic and transcriptomic investigations of the transition from egg-laying to live birth

Viviparous (live-bearing) vertebrates have evolved repeatedly within otherwise oviparous(egg-laying) clades. The oviparity to viviparity transition requires numerous physiological,morphological, and immunological changes to the female reproductive tract, including eggshellreduction; delayed oviposition; placental development for supply of water and nutrition to theembryo by the mother; enhanced gas exchange; and suppression of maternal immune rejection ofthe embryo. Genomic and transcriptomic analyses of a closely related oviparous–viviparous pairof lizards (Phrynocephalus przewalskii and P. vlangalii) reveal the changes that account for thesetransitions. In addition, we compared the gene sequences in transcriptomes of four oviparous–viviparous pairs of lizards in different genera to look for possible gene convergence at thesequence level.