Comparison of the most significantly regulated genes in our study (p < 0.01, 737 genes; Table S1) to those identified in 2 previous studies of gene expression regulation by ethanol exposure in Drosophila revealed a small set of genes detected by all studies (Fig. 2H; Morozova et al., 2006; Urizar et al., 2007). Of the 29 commonly identified genes, 25 showed the same direction of expression regulation (increase or decrease) in all 3 studies (Table S3). Twelve of the commonly regulated genes are annotated with GO terms for metabolic and biosynthetic processes, and these included 3 up-regulated genesencoding proteins involved in serine biosynthesis (aay, CG3011, CG8129; Table 1). l-Serine is important in protein and phospholipid synthesis, and d-serine can act as a co-agonist with glutamate at N-methyl-d-aspartate (NMDA) receptors (Oliet and Mothet, 2009). Serine is mainly synthesized from the glycolysis intermediate 3-phosphoglycerate in a 3-step enzymatic process; the Drosophila gene astray encodes the terminal enzyme 3-phosphoserine phosphatase. Serine is also synthesized from glycine by glycine hydroxylmethyltransferase, which is encoded by the Drosophila gene CG3011.Serine racemase converts l-serine to d-serine (Oliet
