in overall expression levels that are nonetheless critical for the behavioral actions of ethanol. We detected gene expression changes that overlapped with those identified in 2 previous studies of the effects of ethanol exposure in Drosophila (Morozova et al., 2006; Urizar et al., 2007). The overlap of gene expression regulation detected was small, but the direction of the regulation was remarkably consistent, indicating both that the quality of the expression data from all studies was high, and that some biological processes are engaged by ethanol presented at varied concentrations, lengths of time, and frequency. Increased expression of 3 genes-encoding serine synthesis enzymes was a prominent effect of ethanol exposure that was detected across studies, and our preliminary mutational analysis of 2 of these genes (the 3-phosphoserine phosphatase-encoding aay and the glycine hydroxymethyl-transferase encoding CG3011) supports a role for serine in behavioral responses to acute and repeated ethanol exposures (Table S5). Serine is involved in protein and phospholipid synthesis, but also acts as a co-agonist for NMDA signaling (Oliet and Mothet, 2009). Any or all of these roles for serine may be affected by increased serine synthesis following ethanol exposure. Alterations in membrane lipid physiology correlate with resistance to lethal ethanol
