The shrimp FAMeT cDNA is encoded for a putative enzyme involved in the methylfarnesoate (MF) biosynthetic pathway and is temporally expressed in the eyestalk of different sexes

Methylfarnesoate (MF), an analogue of the insect juvenile hormone III, has been implicated to play a vital role in the regulation of the growth and re productive development in crustaceans. Farnesoic acid O-methyltransferase ( FAMeT) is the key enzyme involved in catalyzing the final step in the MF bi osynthetic pathway. In this study, we report the cloning and characterizati on of the cDNA encoding the putative FAMeT of the shrimp Metapenaeus ensis. FAMeT comprises 280 amino acid residues with a predicted molecular weight of 32 kDa. The predicted putative FAMeT protein reveals a high degree of st ructural conservation of FAMeT with the lobsters. It shares 79 and 70% sequ ence identities with the putative FAMeTs of Homarus americanus and Panuliru s interruptus, respectively. As revealed by the Southern blot analysis and genomic PCR, only one gene exists in the shrimp genome and the gene is unin terrupted in the coding region. The shrimp FAMeT mRNA is widely distributed in many tissues with the highest expression level observed in the central nervous system. A constant level of FAMeT expression is recorded in the ven tral nerve cord of the juveniles and the mature females during the reproduc tive cycle. Unlike the ventral nerve cord, the eyestalk of the juvenile mal e, but not the female, expresses FAMeT. Further study shows that the eyesta lk of the mature female expresses FAMeT during all stages of ovarian matura tion. We spectulate that FAMeT may be important for the regulation of eyest alk neuropeptides. This is the first extensive study on the molecular chara cterization, structural analysis and expression of the crustacean FAMeT. (C ) 2001 Elsevier Science Ltd. All rights reserved.