The role of Aspergillus nidulans polo-like kinase PlkA in microtubule-organizing center control

Centrosomes are important microtubule-organizing centers (MTOC) in animal cells. In addition, non-centrosomal MTOCs (ncMTOCs) have been described in many cell types. The functional analogs of centrosomes in fungi are the spindle pole bodies (SPBs). In Aspergillus nidulans, additional MTOCs have been discovered at septa (sMTOC). Although the core components are conserved in both MTOCs, their composition and organization are different and dynamic. Here, we show that the polo-like kinase PlkA binds the gamma-tubulin ring complex (gamma-TuRC) receptor protein ApsB and contributes to targeting ApsB to both MTOCs. PlkA coordinates the activities of the SPB outer plaque and the sMTOC. PlkA kinase activity was required for astral MT formation involving ApsB recruitment. PlkA also interacted with the gamma-TuRC inner plaque receptor protein PcpA. Mitosis was delayed without PlkA, and the PlkA protein was required for proper mitotic spindle morphology, although this function was independent of its catalytic activity. Our results suggest that the pololike kinase is a regulator of MTOC activities and acts as a scaffolding unit through interaction with gamma-TuRC receptors.

Automated summary

Centrosomes are essential microtubule-organizing centers in animal cells, while spindle pole bodies serve as functional analogs in fungi. Additional MTOCs have been identified in Aspergillus nidulans, with differing composition and organization from centrosomes. The polo-like kinase PlkA plays a crucial role in coordinating MTOC activities by interacting with gamma-tubulin ring complex receptors.