The effect of the si gene on glucose adaptation ability in fish

Abstract

To investigate the role of the si gene in the utilization of high-carbohydrate diets in fish, we generated a zebrafish (Danio rerio) model with si gene knockout using the CRISPR/Cas9 genome editing system. A homozygous F₂ mutant line with a 119 bp deletion in the si gene was successfully obtained. We evaluate the high-carbohydrate adaptability of zebrafish using growth traits. Under high-glucose dietary conditions, si knockout significantly impaired zebrafish growth. High-glucose tolerance analysis revealed that si⁻/⁻ mutants exhibited marked glucose utilization dysfunction. Specifically, in diets containing 45 % and 36 % glucose, the body weight of si⁻/⁻ individuals decreased by 21.9 % (45 % glucose diet) and 34.7 % (36 % glucose diet) compared to wild-type (WT) fish (P < 0.05), respectively; body length decreased by 6.9 % and 21.1 % (P < 0.05); and body height decreased by 9.8 % and 19.3 % (P < 0.05). However, under a high-protein diet based on Artemia (brine shrimp), no significant differences were observed in body weight, length, or height between WT and si⁻/⁻ fish (P > 0.05). confirming that si gene specifically regulates high-glucose adaptation.

Mechanistic studies demonstrated that si deletion led to: (1) significant intestinal folds shortening (P < 0.0001) and structural disorganization; (2) altered expression of genes associated with glucose metabolism (GO:0006006) and insulin-like growth factor receptor signaling (GO:0048009) in the intestinal transcriptome; and (3) dysregulation of hepatic glycolysis and energy metabolism pathways. These findings reveal a novel tripartite regulatory mechanism—intestinal folds morphology–digestive absorption–metabolic regulation—through which si gene governs glucose utilization in fish.

This study is the first to systematically demonstrate the critical role of the si gene in dietary glucose utilization in zebrafish, highlighting its involvement in maintaining energy homeostasis through modulation of glucose metabolism and digestive function. These findings provide a theoretical foundation for applying gene editing technologies to improve carbohydrate utilization efficiency in aquaculture breeding programs.