Fission yeast Myo51 is a meiotic spindle pole body component with discrete roles during cell fusion and spore formation

Abstract

Class V myosins are dimeric actin-associated motor proteins that deliver cellular cargoes to discrete cellular locations. Fission yeast possess two class V myosins, Myo51 and Myo52. Although Myo52 has been shown to have roles in vacuole distribution, cytokinesis and cell growth, Myo51 has no as yet discernible function in the vegetative life cycle. Here, we uncover distinct functions for this motor protein during mating and meiosis. Not only does Myo51 transiently localise to a foci at the site of cell fusion upon conjugation, but overexpression of the Myo51 globular tail also leads to disruption of cell fusion. Upon completion of meiotic prophase Myo51 localises to the outside of the spindle pole bodies (SPBs), where it remains until completion of meiosis II. Association of Myo51 with SPBs is not dependent upon actin or the septation initiation network (SIN); however, it is dependent on a stable microtubule cytoskeleton and the presence of the Cdc2-CyclinB complex. We observe a rapid and dynamic exchange of Myo51 at the SPB during meiosis I but not meiosis II. Finally, we show that Myo51 has an important role in regulating spore formation upon completion of meiosis.