Genome-wide identification of MKK and MAPK gene families and their expression analysis under abiotic stress in largemouth bass (Micropterus salmoides)

Mitogen-activated protein kinase (MAPK) cascades, which is a serine-threonine protein kinase, are central to the regulatory network under multiple stresses. However, they have not been systematically investigated in eury-thermic fish. In the present work, a total of 8 mitogen-activated protein kinase kinases (MKKs) and 14 MAPKs were identified in largemouth bass, a kind of typical eurythermic freshwater fish. The phylogenetic and motif analysis results showed that MKKs were classified into 5 subfamilies and MAPKs were classified into 3 subgroups containing ERK, JNK, and p38. The results based on multiple sequence alignments, motif analysis and gene structure analysis supported that MKKs and MAPKs are relatively conserved. Expression profiling revealed that MKK and MAPK genes exhibited constitutive expression patterns in different tissues of largemouth bass. Spe-cifically, 8 genes were differentially expressed after cold stress. Finally, a protein and protein network analysis indicated that MKK and MAPK proteins might be involved in the response to cold stress by regulating apoptosis and proteasome-related pathways. This study could provide valuable information for functional research of MAPKs and MKKs in eurythermic freshwater fish and lay a foundation for further studies to better understand the regulatory mechanism involved in cold stress, which will consequently contribute to the sustainability of aquaculture.