The Sec14 family glycerophospholipid-transfer protein is required for structural integrity of the spindle pole body during meiosis in fission yeast

Abstract

The fission yeast spo20+ gene encodes a glycerophospholipid-transfer protein. spo20 mutants are unable to assemble the forespore membrane properly. Here we studied the structural integrity of the spindle pole body (SPB) in spo20-H6 mutants during meiosis. Meiotic cells expressing a GFP-tagged SPB marker protein, Spo15-GFP, showed an excess number of SPBs, some of which were not localized to the spindle poles and were termed 'pseudo-SPBs'. Formation of spindles for meiosis I was significantly delayed in spo20-H6 cells, although the morphology of spindles and segregation of the sister chromatids seemed normal. The SPB of spo20-H6 contained meiosis-specific outer plaques, though outermost layers were less evident. Time-lapse studies of spo20-H6 cells showed that the pseudo-SPBs originated from normal SPBs at the spindle poles during meiosis I. Among the SPB components tested, Spo15, Spo13, Sad1 and Cut12 were localized to the pseudo-SPBs, but Sid4 was not always present. Alp4, a component of the γ-tubulin complex, was also present in about 40% of the pseudo-SPBs.The forespore membranes initiated from both the SPBs and the pseudo-SPBs. We conclude that Spo20 plays a role in maintaining the structural integrity of the meiotic SPB, besides supplying membrane vesicles for forespore membrane assembly. © Blackwell Publishing Limited.