Amylase mRNA expression in Crassostrea gigas during feeding cycles

A Crassostrea gigas digestive gland copy DNA (cDNA) library constructed in the lambda phage ZapII (Stratagene, La Jola, USA) was screened with an amyl ase heterologous probe. To get access to the complete cDNA, a polymerase ch ain reaction extension was conducted using DNA extracted from the phages. T he complete cDNA sequence is 1688 base pairs (EMBL = YO8370). The deduced p rotein sequence is 519 aminoacids long with a 19 aminoacid signal peptide. Similarity with Pecten maximus amylase is 72%. A 3-day nutrition experiment with a cyclic algal food supply was carried out. Amylase enzyme activities and mRNAs were individually measured on five animals, nine times a day. Me ssenger RNAs were quantified by dot hybridization using the previously char acterized cDNA as probe. Variation of amylase mRNA was observed, in relatio n with the level of activity of the enzyme. Coordinated changes in PNA and enzyme levels suggested a possible transcriptional regulation of amylase in C, gigas as in vertebrates.