The fission yeast SPB component Dms1 is required to initiate forespore membrane formation and maintain meiotic SPB components.

Touko Niimi,Taro Nakamura

doi:10.1371/journal.pone.0197879

Abstract

The spindle pole body (SPB) plays a central role in spore plasma membrane formation in addition to its recognized role in microtubule organization. During meiosis, a biomembrane called the forespore membrane (FSM) is newly formed at the SPB. Although several SPB proteins essential for the initiation of FSM formation (meiotic SPB components) have been identified, the molecular mechanism is still unknown. Here, we report the isolation and functional characterization of Dms1 as a component of the SPB. We show that FSM formation does not initiate in dms1Δ cells. Dms1 protein is constitutively expressed throughout the life cycle and localizes to the SPB and the nuclear envelope. The predicted Dms1 protein has a transmembrane domain, which is required for correct localization at the SPB. Dms1 is essential for the proper localization of three meiotic SPB components, Spo15, Spo2, and Spo13, but these components do not affect localization of Dms1. Collectively, these results suggest that Dms1 anchors these meiotic SPB components to the SPB, thereby facilitating the initiation of FSM formation.

Highlights

The fission yeast Schizosaccharomyces pombe cells enter sporulation under nutrient starvation, when nitrogen is the limiting nutrient [1,2,3]
Our analysis provides mechanistic insight into the regulation of meiotic spindle pole body (SPB) components to ensure the correct initiation of forespore membrane (FSM) formation
Our findings suggest the possibility that Dms1 anchors other meiotic SPB components to the SPB, thereby regulating the initiation of FSM formation

Summary

Introduction

The fission yeast Schizosaccharomyces pombe cells enter sporulation under nutrient starvation, when nitrogen is the limiting nutrient [1,2,3]. Sporulation consists of two overlapping processes, meiotic nuclear division and spore morphogenesis. The main event of the latter process is the formation of a double-layered intracellular membrane, called the forespore membrane (FSM). Formation of the FSM initiates during meiosis II. The FSM expands by vesicle fusion and eventually encapsulates each of the four nuclei generated. The inner layer of the FSM becomes the spore plasma membrane, while the outer layer is degraded by autolysis [4, 5]

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