Abstract: 【Aim】To clone and identify fork head transcription factor 1 gene in the onion fly, Delia antiqua, so as to explore its roles in sugar and lipid metabolism in the summer prediapause pupae of this insect. 【Methods】 The full-length open-reading frame of fork head transcription factor 1 gene was cloned based on the transcriptome data of D. antiqua by 3′ RACE method. The sequence characteristics, conserved domains and secondary structure of its encoded protein were analyzed using bioinformatic approaches. A maximum-likelihood phylogenic tree was constructed for the target protein and homologues from other thirteen insect species. After the target gene was silenced in the summer prediapause pupae of D. antiqua by RNA interference, the expression levels of its downstream genes including brummer gene (DaBmm) and phosphoenol-pyruvate carboxykinase gene (DaPepck) were measured by qPCR, and the contents of triacylglycerol (TAG), treaholse and glucose, and the total lipase activity were analyzed. 【Results】 The full-length cDNA sequence of the fork head transcription factor 1 gene DaFOXO1 was cloned from D. antiqua, and deposited in the GenBank under the accession number MG813258. It encodes a 619-amino-acid protein with a typical fork head DNA binding domain, nuclear localization signal, two14-3-3binding motifs and a glutamine-rich domain. DaFOXO1 shares 87% sequence identity with FOXO1 of Lucilia cuprina at the amino acid level and they are clustered together. DaFOXO1 knockdown in the summer prediapause pupae of D. antiqua significantly suppressed the expression of DaBmm between 8 h and 20 h after treatment, significantly affected the TAG content and total lipase activity between 12 h and 24 h after treatment, and significantly decreased the expression level of DaPepck between 8 h and 20 h(except 16 h) after treatment. Neither glucose content nor trehalose content in the dsDaFOXO1-treated summer prediapause pupae of D. antiqua significantly changed. 【Conclusion】 The results indicate that the accumulation of trehalose and glucose has completed before pupation, and the regulatory role of DaFOXO1 inthe expressions of DaBmm and DaDepck may contribute to the accumulation of lipid in the summer prediapause pupae of D. antiqua. The results also suggest that targeting Bmm-dependent lipolysis and its downstream factors may provide a strategy to disrupt insect diapause.

Key words: Delia antiqua, summer diapause, RNA interference, lipid metabolism, sugar metabolism