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J. Cell Biol.,
Volume 140, Number 1, January 12, 1998 81-90
Department of Pharmacological Sciences, State University of New York, Stony Brook, Stony Brook, New York 11794-8651
Phospholipase D (PLD) enzymes catalyze
the hydrolysis of phosphatidylcholine and are involved
in membrane trafficking and cytoskeletal reorganization. The Saccharomyces cerevisiae SPO14 gene encodes a PLD that is essential for meiosis. We have analyzed the role of PLD in meiosis by examining two
mutant proteins, one with a point mutation in a conserved residue (Spo14pK
H) and one with an amino-terminal deletion (Spo14p
N), neither of which can restore meiosis in a spo14 deletion strain. Spo14pK H is
enzymatically inactive, indicating that PLD activity is
required, whereas Spo14pN retains PLD catalytic activity in vitro, indicating that PLD activity is not sufficient for meiosis. To explore other aspects of Spo14
function, we followed the localization of the enzyme during meiosis. Spo14p is initially distributed throughout the cell, becomes concentrated at the spindle pole
bodies after the meiosis I division, and at meiosis II localizes to the new spore membrane as it surrounds the
nuclei and then expands to encapsulate the associated
cytoplasm during the formation of spores. The catalytically inactive protein also undergoes relocalization during meiosis; however, in the absence of PLD activity, no
membrane is formed. In contrast, Spo14pN does not
relocalize properly, indicating that the failure of this
protein to complement a spo14 mutant is due to its inability to localize its PLD activity. Furthermore, we
find that Spo14p movement is correlated with phosphorylation of the protein. These experiments indicate that
PLD participates in regulated membrane formation
during meiosis, and that both its catalytic activity and
subcellular redistribution are essential for this function.
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