RNA interference reveals chloride channel 7 gene helps short-term hypersalinity stress resistance in Hong Kong oyster Crassostrea hongkongensis

The chloride channel 7 gene (CLC7) of the Hong Kong oyster Crassostrea hongkongensis was cloned and named ChCLC7. The cDNA was 2 572 bp in length, with a 5' non-coding region containing 25 bp, a 3' non-coding region containing 327 bp, and an open reading frame of 2 298 bp. ChCLC7 has 96.8% and 92.1% homology with CLC7 of Crassostrea gigas and Crassostrea virginica, respectively, and it was clustered with CLC7 of C. gigas and C. virginica. QRT-PCR showed that ChCLC7 was expressed in all eight tissues, with the highest in adductor muscle and second in gill. The ChCLC7 expression pattern in gill was altered significantly under high salinity stress with an overall upward and then downward trend. After RNA interference, the expression of ChCLC7 and survival rate of oyster under high salinity stress was reduced significantly, and so did the concentration of hemolymph chloride ion in 48-96 h after RNA interference. We believed that ChCLC7 could play an important role in osmoregulation of C. hongkongensis by regulating Cl- transport. This study provided data for the analysis of molecular mechanism against oyster salinity stress.