Sesquiterpenoid pathway in the mandibular organ of Penaeus monodon: Cloning, expression, characterization of PmJHAMT and its alteration response to eyestalk ablation

• Main Author: Semchuchot W.
• Other Authors: Mahidol University
• Format: Article
• Published: 2023
• Subjects: Agricultural and Biological Sciences
• Online Access: https://repository.li.mahidol.ac.th/handle/123456789/81466

Methyl farnesoate (MF), a crustacean equivalent of juvenile hormone (JH) of insects, is known to be produced from the mandibular organ (MO). This study reports transcriptome analysis of Penaeus monodon MO and identifies putative genes encoding enzymes in the sesquiterpenoid pathway. A total of 44,490,420 clean reads were obtained and utilized for subsequent analysis. De novo assembly created 31,201 transcripts and 31,167 unigenes. To archive the functional annotation, all unigenes were annotated with KOG, KEGG, and GO. Putative genes encoding enzymes and regulatory proteins involved in the sesquiterpenoid pathway were obtained from the MO transcriptome data based on the conserved domains and sequence homology. They included S-adenosylmethionine synthetase, farnesyl pyrophosphate synthase, short chain dependent dehydrogenase/reductase (SDR), NAD(P) + -dependent aldehyde dehydrogenase, S-adenosylmethionine-dependent methyltransferases or juvenile hormone acid-O-methyl transferase (JHAMT), farnesoic acid O-methyl transferase (FAMeT), juvenile hormone binding protein, cytochrome C/P-450 family 15 (CRYP15A1)/methylfarnesoate epoxidase (MFE), juvenile hormone epoxide hydrolase (JHEH), and juvenile hormone esterase (JHE). We first identified and characterized JHAMT orthologs in P. monodon (PmJHAMT). The complete cDNA sequence of PmJHAMT consisted of 1,221 nt encoded 271 amino acids with a conserved S-adenosyl methionine (SAM) binding domain. Phylogenetic analysis clustered PmJHAMT into the group JHAMT with the same clade of the crab Portunus trituberculaus JHAMT. Moreover, the predicted three-dimensional structure of PmJHAMT showed remarkable similarity with the recent crystal structure of the Bombyx mori JHAMT homodimer. RT–PCR analysis revealed that PmJHAMT was exclusively expressed in MO and initially expressed at stage 3 postlarvae. In situ hybridization with a specific probe to PmJHAMT validated the specific expression of this gene in MO cells. Finally, we evaluated the regulation of MO by eyestalk inhibitory peptides. Diminishing MO inhibitory hormone through unilateral eyestalk ablation resulted in a significantly higher expression of PmJHAMT in MO by quantitative PCR. This result indicated that the eyestalk inhibitory hormone inhibited MF synthesis by PmJHAMT gene suppression in the MO. This finding provides insight into the crustacean sesquiterpenoid pathway and improves our understanding of crustacean endocrinology.