Polo-like kinases (Plks) are evolutionarily conserved serine/threonine protein kinases playing crucial roles during multiple stages of mitosis and cytokinesis in yeast and animals. Plks are characterized by a unique Polo-box domain, which plays regulatory roles in controlling Plk activation, interacting with substrates and targeting Plk to specific subcellular locations. Plk activity and protein abundance are subject to temporal and spatial control through transcription, phosphorylation and proteolysis. In the early branching protists, Plk orthologues are present in some taxa, such as kinetoplastids and Giardia, but are lost in apicomplexans, such as Plasmodium. Works from characterizing a Plk orthologue in Trypanosoma brucei, a kinetoplastid protozoan, discover its essential roles in regulating the inheritance of flagellum-associated cytoskeleton and the initiation of cytokinesis, but not any stage of mitosis. These studies reveal evolutionarily conserved and species-specific features in the control of Plk activation, substrate recognition and protein abundance, and suggest the divergence of Plk function and regulation for specialized needs in this flagellated unicellular eukaryote.

Polo 样激酶 (Plk) 是进化上保守的丝氨酸/苏氨酸蛋白激酶，在酵母和动物的有丝分裂和胞质分裂的多个阶段中发挥着至关重要的作用。 Plk 的特点是具有独特的 Polo-box 结构域，该结构域在控制 Plk 激活、与底物相互作用以及将 Plk 靶向特定的亚细胞位置方面发挥调节作用。 Plk 活性和蛋白质丰度通过转录、磷酸化和蛋白水解受到时间和空间控制。在早期分支原生生物中，Plk 直系同源物存在于一些类群中，例如动质体和贾第鞭毛虫，但在顶端复门类中丢失，例如疟原虫。通过表征布氏锥虫（一种动质体原生动物）中的 Plk 直系同源物，发现其在调节鞭毛相关细胞骨架的遗传和胞质分裂启动中的重要作用，但不是有丝分裂的任何阶段。这些研究揭示了在控制 Plk 激活、底物识别和蛋白质丰度方面的进化保守性和物种特异性特征，并表明在这种有鞭毛的单细胞真核生物中，Plk 功能和特殊需求的调节存在差异。