Acetyl-CoA C-acetyltransferase(AACT)is the starting enzymes in mevalonate pathway of terpenoids biosynthesis.To reveal the function of this enzyme during the ovarian development of the crustaceans,we used reversed transcript PCR(RT-PCR)and rapid amplification of cDNA ends(RACE)techniques to clone the AACT(GeneBank accession number:KM033231).The full length of Pt-AACT is 1 630 bp,including a 5'-untranslated region(UTR)of 101 bp,a 3'-UTR of 395 bp and an opening reading frame(ORF)of 1 134 bp encoding 377 amino acid protein.The structures of AACT proteins have two special conserved sequences of thiolase,belonging to stable hydrophobic proteins without an obvious transmembrane region.The deduced amino acid sequence of Pt-AACT exhibited the highest identity(72%)with AACT of Nasonia vitripennis and Aedes aegypti.The phylogenetic tree analysis showed that Pt-AACT was clustered in insect AACTs.Tissue distribution by quantitative real-time PCR(qRT-PCR)illustrated that the Pt-AACT was most highly expressed in the MOs.During the ovarian development,expression of Pt-AACT in MOs significantly remained the highest level at stage Ⅰ.Therefore,AACT plays an important role in ovarian development regulation of P.Trituberculatus.