Molecular analysis of a developmentally regulated gene required for Dictyostelium aggregation

We have previously shown that the developmentally regulated gene D2 is induced during aggregation by pulses of cAMP, which act via the cell surface receptor and consequent signal transduction pathways (W. Rowekamp and R.A. Firtel, 1980, Dev. Biol. 79, 409-418; S.K.O. Mann and R.A. Firtel, 1987, Mol. Cell. Biol. 7, 458-469; S.K.O. Mann, C. Pinko, and R.A. Firtel, 1988, Dev. Biol., in press). In this manuscript, we compare the complete derived amino acid sequence for D2 to two cloned and sequenced eukaryotic esterases and examine the requirement of the D2 gene product for development. Amino acid sequence data comparisons suggest that D2 encodes a serine esterase with strong sequence identity to Torpedo acetylcholine esterase and a Drosophila esterase. The protein has a putative leader sequence, suggesting that it is shunted into vesicles. Using an antisense gene construct driven by a Discoidin I promoter, whose transcriptional activity depends on the growth conditions of the cells, we show that inhibition of D2 mRNA accumulation results in an abnormal developmental program that includes the absence of normal streaming and incomplete aggregate formation and subsequent development. We suggest that D2 encodes an esterase function required for proper aggregation and subsequent development.