Autophagy is an important cellular response to starvation and stress, and plays critical roles in embryogenesis, development, cell death, cancer, and immunity. Beclin-1 is one of the central regulators of autophagy in mammals. In the present study, we isolated a PoBeclin-1 cDNA from the olive flounder (Paralichthys olivaceus) by screening a flounder gill cDNA library and rapid amplification of cDNA ends (RACE). The PoBeclin-1 cDNA we isolated encodes a 447-amino acid polypeptide containing a conserved Bcl-2-binding domain. The deduced amino acid sequence of PoBeclin-1 showed high degrees of sequence identity (80.5-95.3%) with Beclin-1 from human, frog, mouse, zebrafish, and pufferfish. PoBeclin-1 transcripts were detected from 1 day post-hatching and were found to be ubiquitously expressed in the healthy flounder. Expression of PoBeclin-1 mRNA was increased in the kidney and spleen of flounders challenged with viral hemorrhagic septicemia virus (VHSV). When infected with VHSV, PoBeclin-1-overexpressing HINAE cells had low level (about 26%) of VHSV G transcripts compared to control cells. Taken together, these results suggest that PoBeclin-1 may play a role in the innate immune response to viral infection in the flounder. (C) 2011 Elsevier Ltd. All rights reserved.