Cloning of adsl gene in Larimichthys crocea and analysis of its correlation between expression level and inosine content

Declining flesh quality in farmed large yellow croaker (Larimichthys crocea) seriously restricts the healthy development of its industry. To investigate the role of adenylsuccinate lyase (ADSL) in the synthesis of the key flavor substance inosine monophosphate (IMP) in L. crocea, we cloned the open reading frame (ORF) sequence of its adsl gene and analyzed the gene structure and evolutionary characteristics. After clarifying its tissue distribution characteristics, we compared the differences in IMP content and adsl gene expression in muscle tissues of cultured L. crocea with different sizes. The results show that the ORF cDNA of adsl was 1 446 bp and encoded a polypeptide of 481 amino acids (aa). The corresponding protein had a relative molecular weight of 54.6 kD and an isoelectric point of 6.19, including Pfam Lyase_1 (Ala²⁴−Leu³⁰⁹) and ADSL_C (Leu³⁷⁴−Leu⁴⁵⁸) structural domains. Phylogenetic analysis of the deduced AA sequence reveals that the genetic relationship between L. crocea and Collechthys lucidus was the closest, with a similarity of 98.54%. The genomic DNA sequence of adsl gene was subdivided into 12 exons and 11 introns. Its mRNA had the highest expression level in muscle tissue and was significantly higher than other tissues (P<0.05). With the increase of body mass, the IMP content in L. crocea muscle increased significantly (P<0.01). The relative expression level of adsl gene mRNA also followed a similar pattern. Correlation analysis shows that the relative expression level of adsl gene in L. crocea muscle was significantly positively correlated with the corresponding IMP content (r=0.962). The results provide references for further sudy on the mechanism of action of adsl gene in IMP synthesis and flavor formation in L. crocea.