Introduction
Striped catfish (Pangasianodon hypophthalmus Sauvage, 1878) is a typical catfish in the Pangasiidae family. It is a migratory and benthic species with a natural origin in the Mekong River and the Chao Phraya River basins (Ali et al, 2013). Due to fast growth, high disease resistance and good adaptability to high density, it is suitable for international intensive production, although it is now predominantly cultured in Vietnam. Influenced by trade and market requirements, striped catfish was introduced to several other Asian countries, such as Singapore, Philippines, Malaysia, India and China (De Silva et al., 2006; Singh & Lakra, 2012). In view of burgeoning trade, the introduction of striped catfish may boost up the aquaculture production in some of these countries (De Silva et al., 2006; De Silva & Soto, 2009). Currently, this catfish species is widely cultured in many Asian countries as an important food source with a great economic significance.
In a previous study, a primary assembly of striped catfish, based on only Illumina short reads, was reported (Kim et al., 2018). In recent years, combination of short reads, long reads and high-resolution chromosome conformation capture (HIC) techniques has been widely employed to improve the quality of many sequenced genomes (You et al., 2020). In this study, we applied this integrated strategy to obtain a chromosome-level genome assembly for the striped catfish with much higher integrity and continuity values.
In addition to fish fillet, fish oil is also one of the important value-added products with unsaturated fatty acids. Striped catfish has been considered as an oily fish along with other freshwater fishes from the Mekong sub-region, such as por fish (Pangasius bocourti ), Mong fish (Pangasius conchophilus ), and Mekong giant catfish (Pangasianodon gigas ; Hemung et al., 2010). The crude fat from head and flab parts of striped catfish sums up to be 58.83%, and unsaturated fatty acids in the crude fat account for 60.28% (Hemung et al., 2010). Striped catfish therefore may be a considerable source of unsaturated fatty acids for human consumption. However, for fish fillet, the high fat content may have a negative impact on the economic value of striped fishes (Van Sang et al., 2012). Hence, body fat of striped fish has become an important trait for any practical breeding program.
By in-depth genomic analysis, we observed a tandem duplication of fatty acid binding protein 1 gene (fabp1 ) in the striped catfish genome. In fact, fabp1 is known to be critical for fatty acid uptake and intracellular transport, and it also plays an important role in regulation of lipid metabolism and cellular signaling pathways (Furuhashi & Hotamisligil, 2008). Since fabp1was proved to be relevant to fatty acid storage, the tandem duplication of fabp1 may be related to the high-fat trait of striped catfish. It may provide a new perspective for molecular breeding of striped catfish with an appropriate body fat content.