Low temperature stress can lead to variety of changes, including apoptosis in tilapia (Oreochromis niloticus). The B cell lymphoma-2 (Bcl-2) gene family plays an important role in the process of apoptosis. The present study conducted genome-wide characterization of the Bcl-2 family genes in tilapia and their mRNA expression profiles were analyzed in different tissues of tilapia under the low temperature stress (10°C). Twenty-four Bcl-2 family genes were identified, containing 2~8 exons. These

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... nes were classified into two subfamilies (Bcl-2 homologs and BH3-only) based on their conserved domains. Besides, these BCL-2 proteins in tilapia possess at least one of the four conserved BH domains. The phylogenetic analysis showed that the Bcl-2 family genes did not aggregate by species, demonstrating sequence conservation of different types of Bcl-2 family members. Real-time quantitative PCR (RT-qPCR) analysis showed that Bcl-2 family genes were broadly expressed in different tissues of tilapia. When reared at 10 °C, the transcriptional expression levels of most of anti-apoptotic Bcl-2 homologs subgroup members and other BH3-only subgroup members in most tissues of tilapia were higher than those at 30°C. However, most of other Bcl-2 family members revealed a lower expression. The results suggested that