Evolution and gene expression of matrix metalloproteinase gene family during gonadal development in Scatophagus argus

During the reproductive cycle of Scatophagus argus (S. argus), their gonads undergo degeneration and re-maturation including the degradation of proteins in the extracellular matrix (ECM). Matrix metalloproteinases (MMPs), a family of zinc proteases, play a crucial role in ECM degradation.

Our aim was to identify the MMP gene family of S. argus and determine their gene expression levels across various stages of gonadal development.

The MMP gene family of S. argus in the genome was identified by using basic Local Alignment Search Tool (BLAST) and HMMER. Phylogenetic tree and synteny analysis were performed to investigate the evolutionary past of the MMP gene family. The gonads of 18 S. argus (9 males and 9 females) were dissected and a quantitative reverse transcription polymerase chain reaction (RT-qPCR) was conducted to investigate the expression levels of MMP genes across different stages of gonadal development.

Twenty-three MMP family genes were identified in the genome of S. argus. We divided the MMP gene family into 4 categories and found that teleosts exhibit a higher MMP gene copy number relative to other vertebrates. By sampling S. argus at different stages of gonadal development, we observed an upregulation in relative expression levels of 11 MMP genes in the testis or ovary. Ten MMP genes (mmp2, 9, 14a, 15a, 15b, 16a, 17a, 23b and 24) showed higher mRNA expression in the testis compared to the ovary and mmp28 had higher expression during ovarian development. The tissue distribution results demonstrated that the gills exhibited the lowest relative expression level among all tissues examined. However, 6 genes (mmp2, 9, 14a, 15a, 15b, and 16a) had relatively high expression in all tissues.

The result suggested that teleost-special whole genome duplication was mainly responsible for the formation of the MMP gene family in teleosts. Expression patterns of MMP genes indicated that mmp2, 9, 14a, 15a, 15b, 16a, 17a, 23b and 24 played a vital role in testicular development while mmp28 was more important for ovarian development. Limitaion: Further studies are needed to determine their protein expressions in gonadal development and precise mechanism in gonadal differentiation. The study enhances our understanding of the MMP gene family in evolution of teleost and provides valuable insights for further research on MMPs in S. argus.