Ma X, Øvrebø JI, Thompson EM.

Front Cell Dev Biol. 2022 Jan 28;9:770939. doi:10.3389/fcell.2021.770939

Evolution of CDK1 Paralog Specializations in a Lineage With Fast Developing Planktonic Embryos.

The last common ancestors of all oiks probably had only one CDK1 as Fritillaria borealis also has only 1. Oiks in general have 3 paralogs (a, b, c), and O. dioica has 5 (a, b, c, plus d and e which appear to originate from c). They are found on chr1 (c, e), chr2, (a, b) and the XSR of chr3 (d). CycBa is also found on the XSR, and interacts with CDK1d for functions essential to meiosis of oocytes. In contrary to the ancestral CDK1 in other animals, the levels of CDK1d oscillate. “Interspecies clustering of CDK1 paralogs [show] conservation of their intron-exon structures” “O. dioica CDK1a and b locate on the same autosome whereas CDK1c is present on a different autosome that also contains CDK1e. CDK1d is found on the X chromosome where, at a distance of 5 MB, the CycBa locus is also located.” “The PSTAIRE helix is modified in all Oikopleura CDK1 paralogs whereas Oikopleura CDK2s retain the canonical PSTAIRE sequence. All of the 17 identified Oikopleura CDK1 sequences share the A48S substitution.”