LAUSR

Centrosomes are important microtubule-organizing centers (MTOC) in animal cells. In addition, non-centrosomal MTOCs (ncMTOCs) were described in many cell types. Functional analogs of centrosomes in fungi are the spindle pole bodies (SPBs). In Aspergillus nidulans additional MTOCs were 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 γ-tubulin ring complex (γ-TuRC) receptor protein ApsB and contributes to targeting ApsB to both MTOCs. PlkA coordinates SPB outer plaque with sMTOC activities. PlkA kinase activity was required for astral MT formation involving ApsB recruitment. PlkA also interacted with the γ-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 polo-like kinase as a regulator of MTOC activities and as a scaffolding unit through interaction with γ-tubulin ring complex receptors.