A novel <i>Toxoplasma</i> aurora-related kinase shows dynamic association with parasite cytoskeletal structures.

<p>Periodicity of TgArk1 mRNA (A) translates into dynamic cell cycle protein expression (B) (for raw mRNA data, see <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002093#pbio.1002093.s001" target="_blank">S1 Data</a>). At peak expression in S/M phase, TgArk1^HA protein (red, 3xHA tagged in genome by knock-in) was co-localized to the centrosome outer core complex as demonstrated by the anti-HA (red) and anti-Centrin (green) co-staining. Intriguingly, as parasites entered mitosis, TgArk1^HA also became localized to a discrete linear structure. The dual pattern of localization in the centrosome outer core (TgArk1, head morphology) and the novel linear structure (TgArk1, tail morphology) was altered further in late cytokinesis (last two panels) when TgArk1 disappeared from the TgCentrin1-associated outer core complex. Magnified images of the specific areas within the merged panels are shown to the right. Cell cycle stages are indicated in the upper left of each image series. (C) Co-staining with anti-TgMORN1 (green) antibody showed that association of TgArk1^HA with the centrosome is maintained during centrocone development and duplication. The linear structure stained by TgArk1^HA (tail morphology) is unusual and runs along one side of the growing daughter bud. Yellow dotted line in the magnified image of the cytokinesis stage represents a cytoskeleton of the growing daughter bud. Cell cycle stages are indicated in the upper left of each image series. (D) Treatment of tachyzoites with 2.5 μM oryzalin for 24 h to disrupt subpellicular microtubules indicates the linear TgArk1^HA-tail is an unknown cytoskeletal structure, although the primary association may also involve the factors of the inner membrane complex because TgArk1^HA staining was retained with the disrupted IMC1-containing material after oryzalin caused disassembly of the daughter subpellicular microtubules. Dotted line outlines boundary of the parasitophorous vacuole in the infected host cell.