Dietary supplementation of Synechococcus elongatus PCC 7942 expressing a heterologous β-glucosidase on the expression of genes related to digestion, immune system, and antioxidant defenses of the shrimp Litopenaeus vannamei

Cyanobacteria are a rich source of nutrients in addition to producing bioactive compounds capable of stimulating the immune system of hosts. Also, they can be manipulated with relative ease to produce heterologous proteins. In the present study, a strain of Synechococcus elongatus (PCC7942) was manipulated to produce a prokaryotic β-glucosidase. This strain was added to the diet of Pacific white shrimp Litopenaeus vannamei for 45 days and parameters such as growth performance, proximate composition of muscle tissue and expression of genes related to digestion, amino acid metabolism, immune system and antioxidant defenses were evaluated. Histology of shrimp hepatopancreas was also performed. Transgenic cyanobacteria did not produce negative effects on shrimp growth performance. Regarding proximate composition, an increase in lipid and phosphorus deposition was observed in the muscle of shrimp, as well as lipid in hepatopancreas. Furthermore, an increase in expression of genes related to the immune system (tgase) as well as carbohydrate metabolism and amino acid metabolism (gdh) was observed. It was observed also that both strains of cyanobacteria (wild and transgenic) produced effects on carbohydrate metabolism (increased amy expression) and digestive system (decreased cathB expression). It is possible that cyanobacteria in the diet may be serving as a source of carbohydrates, reducing the use of proteins as a source of energy. It can be concluded that transgenic cyanobacteria had a beneficial effect on shrimp by increasing lipid deposition in muscle and hepatopancreas as well as phosphorus absorption from feed, which can minimize the environmental impact of shrimp farms.