Sma1p is a protein specifically expressed during sporulation in
S. cerevisiae. It has been identified during a screen for genes
required for meiosis and spore formation (Rabitsch et
al., Curr. Bio., 11:1001-1009, 2001). Indeed spore production is severely
impaired in Δsma1 cells. Electron microscopy images of
Δsma1 cells show that the prospore membrane (PSM) is
strongly reduced in size and its growth is abnormal. In order to localize
Sma1p during sporulation, a GFP tagged form has been used showing that
Sma1-GFP localizes specifically on the PSM. We searched for interacting
proteins in sporulating cells using a ProteinA tagged form of Sma1p as
bait and we identified Spo14p. Spo14p is a phospholipase D and it cleaves
phosphatidylcholine generating phosphatidic acid and choline. Spo14p
localizes on PSM during sporulation and its enzymatic activity is
necessary for PSM formation (Rudge et al., JCB, 140-1:81-90, 1998). We
verified the interaction between Sma1p and Spo14p by
coimmuneprecipitation. Meiotic and mitotic overexpressed forms of
SMA1 show that Sma1p is specifically modified during meiosis. The
nature of this modification is still unknown but the mitotic form is
still able to coimmuneprecipitate with 3HA-Spo14p suggesting that its
modification is not required for the interaction. These data highlight
Sma1p as a new important factor for regulation of prospore membrane
growth and suggest a link with Spo14p known to be essential for PSM
formation.