Abstract: This experiment involved the artificial infection of Clarias gariepinus with Aeromonas veronii. Based on the transcriptome data of the spleen from healthy C. gariepinus and those infected for 3, 24, and 48 hours, the expression levels of the c-type lysozyme Unigene sequence and c-type lysozyme gene were analyzed. The results revealed that the c-type lysozyme Unigene sequence was 742 bp long, with the coding sequence（CDS）region spanning from position 99 to 539, totaling 441 bp. At positions 257 and 502, there were transitions of G→A and C→T bases, while at position 86, there were multiple base insertions or deletions, resulting in two genotypes: GGTCTAA and G------. The expression level of c-type lysozyme in the spleen of C. gariepinus continued to increase within 48 hours post-infection, reaching its peak at 48 hours, significantly higher than the expression levels at 3 and 24 hours post-bacterial infection and that of healthy C. gariepinus spleen. Clustering analysis was performed on the CDS sequences of the c-type lysozyme gene in C. gariepinus and eight other fish species retrieved from NCBI. The results indicated that the similarity between the c-type lysozyme gene CDS sequences of C. gariepinus and Clarias batrachus was the highest, at 95.24%. This study provides preliminary insights into the expression and sequence characterization of c-type lysozyme in the spleen of C. gariepinus, and lays foundation for further in-depth studies on the function of this gene in the immune system.

Key words: Clarias gariepinus, transcriptome analysis, c-type lysozyme, gene expression