2017 Volume 82 Issue 3 Pages 261-266
Polo-like kinase (PLK) is a serine/threonine kinase involved in the formation of the mitotic spindle and the maturation of centrosomes. PLKs are highly conserved in the animal and fungi kingdoms but have disappeared in land plants. Plant PLK orthologs have been found in green algae, red algae and a filamentous terrestrial alga, Klebsormidium flaccidum, which can adapt to both fresh water and land environments. Our evolutionary analyses suggest that plants evolutionally lost the PLK ortholog before the divergence of land plants. Our localization analyses of the PLK ortholog in Cyanidioschyzon merolae demonstrated that it is localized in spindle poles and on mitochondrial polar microtubules, suggesting that plant ancestral PLK functions in the formation of mitotic spindles like animal and fungus PLK orthologs.