A member of the short-chain dehydrogenase/reductase (SDR) superfamily is a target of the ecdysone response in honey bee (Apis mellifera) caste development

Abstract

Many aspects in caste polyphenism result from hormonally controlled differential gene expression. A DDRT-PCR screen for ecdysteroid-regulated genes in ovaries revealed a set of ESTs coding for metabolic enzymes. For a cDNA encoding a short-chain dehydrogenase/reductase (SDR) we obtained the complete coding sequence (246 amino acids), revealing the protein motifs typical of insect SDRs. Its initially high expression in early fifth-instar larvae vanished in prepupae. Expression levels in worker larvae were higher than in queen larvae, suggesting negative regulation by the caste-specific ecdysteroid titer. This finding was confirmed by in vitro exposure of competent worker ovaries to makisterone A. In contrast to whole body RNA extracts, two SDR transcripts were detected in the ovaries. Both had their expression downregulated by makisterone A. Hormonal regulation and tissue-specific expression pattern makes this SDR an interesting enzyme for comparative molecular studies on social insect caste polyphenisms.