GENOMIC ORGANIZATION AND POLYMORPHISM OF A CRUSTACEAN TRYPSIN MULTIGENE FAMILY

The coding sequences of three trypsin genes, obtained by polymerase ch ain reaction (PCR), were determined in Penaeus vannamei (Crustacea, De capoda). These genes were characterised by two short introns, which oc cur at a position quasi-conserved as the first two introns in vertebra te counterparts. Belonging to three different families, two of the gen es are expressed in the digestive gland. A 5' RACE-PCR amplification o f hepatopancreatic mRNA, together with the presence of short 5' extens ions, confirmed that the third gene family is not expressed in this ti ssue. The second intron in the genes expressed in the hepatopancreas p resents a 5' splice site consensus, beginning with a GC motive which i s reported for the first time in trypsin genes and is of phase I in ma mmals. A high copy number was determined for these genes. Several rest ricted PCR were performed to describe the polymorphism of these sequen ces. Five genes were partially sequenced for each family and five gene s coding the different, previously described cDNAs were recovered. The se sequences also confirm that the third family resembles a mosaic of type I and type II gene families. A high degree of polymorphism in the introns (54-59% identity) among the three families is observed, but m utations in corresponding introns inside each of the families are low (3-6%). (C) 1998 Elsevier Science B.V. All rights reserved.