Abstract:  Methyl farnesoate (MF)is the unepoxidized form of insect JH III, and is commonly considered as an equivalent of JH in crustaceans, which plays essential roles in many physiological processes of crustaceans. To investigate the possible role of MF in the molting process of the swimming crab, Portunus trituberculatus, the hemolymph levels were detected using the gas chromatography-mass spectrography (GC-MS)with selected ion monitoring (SIM), and the gene expression of the enzymes in MF biosynthesis pathway was detected using qPCR. The results showed that the hemolymph MF titer increased significantly in the pre-molt stage, and to the maximum in D1 substage. The gene expression patterns of three MF biosynthesis enzymes including AACT, FPS, and JHAMT were not the same during the molt cycle, while still consistent with their location in the MF biosynthesis pathway, which indicated that the transcriptional regulation of MF synthesis enzymes might be cascaded. In addition, the regulatory role of eyestalk factor on the MF biosynthesis was investigated by eyestalk ablation (ESA)experiment. The results showed that ESA could rapidly induce the hemolymph MF titer and the gene expression of MF synthesis enzymes including PtHMGR, PtFPS, PtFAMeT and PtJHAMT, suggesting the existence of transcriptional regulation of eyestalk factors on MF biosynthesis.

Key words: methyl farnesoate, biosynthesis, molting, Portunus trituberculatus, gene expression