RNA extraction, first-strand cDNA synthesis and cloning
RNA was isolated from the gill with TRIzol reagent (Gibco BRL,
Grand Island, NY) according to the manufacturer’s protocol. Total
RNA was precipitated in ethanol, and the RNA pellets were dissolved
in RNase-free water. The quantity and integrity of the
RNA were assessed by spectrophotometry and electrophoresis
through a 1.5% agarose gel. Single-strand cDNA was constructed
using Invitrogen reagents (Carlsbad, CA). Briefly, four micrograms
of total RNA were reverse transcribed to the first-strand cDNA with
oligo(dT)1218 priming and SuperScript II reverse transcriptase
(Gibco BRL) in a 20-ll reaction volume under the following incubation
conditions: 42 C for 60 min, 37 C for 15 min, and 70 C for
15 min to terminate the reaction. The resulting cDNA was used
as a template for the subsequent PCR amplification of the genes
that were used in the present study.