Characterization and expression profile of farnesoic acid O-methyltransferase gene from Indian white shrimp, Penaeus indicus

Methyl farnesoate (MF), a sesquiterpenoid synthesized in the mandibular organ, regulates many physiological processes in crustaceans including growth and reproduction. In the present study, farnesoic acid O-methyltransferase (FAMeT), the key enzyme responsible for final step conversion of famesoic acid (FA) to methyl farnesoate (MF), was cloned and characterized from the nervous tissues of Penaeus indicus. Multiple sequence alignment, prediction of conserved domain regions, phosphorylation sites identification and phylogenetic analysis indicated that putative FAMeT fragment from P. indicus (PiFAMeT), shares a high degree of sequence identity to FAMeT proteins isolated from other crustaceans species. Quantitative real-time PCR analysis revealed ubiquitous expression of PiFAMeT in all the tissues examined, with comparative higher mRNA levels in nervous tissue and ovary. Additionally, the levels of PiFAMeT also showed gradual increase of expression correlating with the advancement in ovarian maturation. Further to support their role in promoting ovarian development, serotonin treatment (5HT, 50 mu g/g body weight) was given to eyestalk intact and unilaterally eyestalk ablated females which resulted in significant increase in PiFAMeT transcript levels at day 7 and day 14. The relatively higher levels of PiFAMeT, reflecting higher levels of MF, suggest a role during secondary vitellogenesis thereby regulating ovarian development in P. indicus. Further research is required to understand the synergistic interaction of MF pathways with serotonergic and other regulatory pathways in regulating ovarian maturation in penaeid shrimps.