(A-D) Glycogen synthase (GlyS) is required for glycogen synthesis in D. melanogaster muscles. PAS staining for glycogen was absent in Dmef2-Gal4/UAS-GlySi muscles (B) compared to control Dmef2-Gal4/UAS-whitei muscles (A). Antiglycogen immunostaining for glycogen was absent in Dmef2-Gal4/UAS-GlySi muscles (D) compared to Dmef2-Gal4/UAS-whitei control muscles (C). 