Meiotic Spindle Pole Bodies Acquire the Ability to Assemble the Spore Plasma Membrane by Sequential Recruitment of Sporulation-specific Components in Fission Yeast

Abstract

The spindle pole body (SPB) of Schizosaccharomyces pombe is required for assembly of the forespore membrane (FSM) during meiosis. Before de novo biogenesis of the FSM, the meiotic SPB forms outer plaques, an event referred to as SPB modification. A constitutive SPB component, Spo15, plays an indispensable role in SPB modification and sporulation. Here, we analyzed two sporulation-specific genes, spo13(+) and spo2(+), which are not required for progression of meiotic nuclear divisions, but are essential for sporulation. Spo13 is a 16-kDa coiled-coil protein, and Spo2 is a 15-kDa nonconserved protein. Both Spo13 and Spo2 specifically associated with the meiotic SPB. The respective deletion mutants are viable, but defective in SPB modification and in the onset of FSM formation. Spo13 and Spo2 localized on the cytoplasmic side of the SPB in close contact with the nascent FSM. Localization of Spo13 to the SPB was dependent on Spo15 and Spo2; that of Spo2 depended only on Spo15, suggesting that their recruitment to the SPB is strictly controlled. Spo2 physically associated with both Spo15 and Spo13, but Spo13 and Spo15 did not interact directly. Taken together, these observations indicate that Spo2 is recruited to the SPB during meiosis and then assists in the localization of Spo13 to the outer surface of the SPB.

Live Observation of Forespore Membrane Formation in Fission Yeast

“…As analyzed by fluorescence microscopy using an anti-Sad1 (an SPB component) antibody, compact dots of SPB are transformed into crescent shapes coincident with the initiation of FSM formation (Hagan and Yanagida, 1995;Ikemoto et al, 2000). These morphological alterations of the SPB are called "SPB modification" (Nakase et al, 2008). After SPB modification, membrane vesicles are then recruited to the vicinity of the modified SPBs, and subsequently fuse there to generate forespore membranes Tanaka and Hirata, 1982).…”

“…To address the molecular mechanism of sporulation, we have identified and analyzed a number of sporulation-specific genes (Bresch et al, 1968;Ikemoto et al, 2000;Asakawa et al, 2001;Nakamura et al, 2001Nakamura et al, , 2002Nakamura et al, , 2005Nakase et al, 2001Nakase et al, , 2004Nakase et al, , 2008Nakamura-Kubo et al, 2003;Yoshida et al, 2005;Ye et al, 2007). Spo2, Spo13, and Spo15 proteins localize to the SPB.…”

“…Spo2, Spo13, and Spo15 proteins localize to the SPB. The morphological transformation of the SPB is not detected in either spo2, spo13, or spo15 mutants, suggesting that these proteins are involved in the initiation of FSM formation (Ikemoto et al, 2000;Nakase et al, 2008).…”

Ectopic Overproduction of a Sporulation-Specific Transcription Factor Induces Assembly of Prespore-Like Membranous Compartments in Vegetative Cells of Fission Yeast

“…In contrast, a typical mitotic spindle formed in cells harboring the control plasmid ( Figure 1B). Prior to FSM formation, a meiotic SPB component Spo13 is expressed in a Mei4-dependent manner and recruited to the SPB, which is essential for initiation of FSM formation (Nakase et al 2008). Spo13-GFP fluoresSupporting information is available online at http:/ /www.genetics.org/ cgi/content/full/genetics.109.106906/DC1.…”

Dma1-dependent degradation of Septation Initiation Network proteins during meiosis inSchizosaccharomyces pombe

“…The spindle pole body (SPB) is remodelled during meiosis II and changes its appearance from a dot to a crescent shape, as visualised by indirect immunofluorescence (Hagan and Yanagida, 1995;Yoo et al, 1973). This requires Spo2p, Spo13p and Spo15p (Ikemoto et al, 2000;Nakamura et al, 2008;Nakase et al, 2008). Vesicles are recruited to the modified SPB and fuse to give rise to the forespore membrane (FSM), which expands outwards from the SPB and encapsulates the nucleus to form the prespore.…”