Adaptive Evolution of the PFK Gene Family in Chinese Longsnout Catfish, Leiocassis longirostris.

The Chinese longsnout catfish is a typical carnivorous fish with a relatively weak ability to utilize glucose. However, the genomic basis for its glucose metabolic adaptation remains unclear. In this study, we used comparative genomics methods to systematically analyze the evolutionary characteristics of glucose metabolism-related genes in the Chinese longsnout catfish, focusing on gene family evolution, patterns of expansion and contraction, and selective pressures. The results indicate that glucose metabolism-related genes have undergone significant reshaping during evolution. Genes involved in glucose digestion, absorption, and insulin signaling pathways demonstrate a tendency toward contraction, while those associated with protein and lipid metabolism exhibit expansion. This pattern is consistent with the species' long-term adaptation to a high-protein, high-fat diet. Comparative analysis further revealed that, compared to fish with different dietary habits, certain key genes involved in glycolysis in the Chinese longsnout catfish exhibit a reduction in copy number. Molecular evolutionary analysis showed that key genes involved in glycolysis and gluconeogenesis (including hexokinase 2 (hk2), phosphofructokinase, muscle/platelet (pfkm/p)) exhibit signs of accelerated evolution or positive selection. Notably, the PFK gene family exhibits complex evolutionary characteristics resulting from the combined effects of gene contraction, rapid evolution, and positive selection. In summary, this study reveals the genomic evolutionary basis for the glucose metabolic adaptation of the Chinese longsnout catfish and identifies the PFK gene family as a key candidate for elucidating its unique glucose metabolic characteristics.