MAPKKK gene family in Dunaliella salina: identification, interaction network, and expression patterns under abiotic stress

Mitogen-activated protein kinase kinase kinase (MAPKKK) is a component of the MAPK cascade pathway that plays an essential role in plant growth, development, and response to biotic and abiotic stress in several plant species. However, the MAPKKK family genes from the green alga Dunaliella salina have not been thoroughly characterized to date. In this study, we performed transcriptome and bioinformatics analyses of the MAPKKK gene family in D. salina . Thirty-three DsMAPKKK genes were identified, and 17 DsMAPKKK cloned genes which can significantly respond to salt, hyperosmotic, and oxidative stresses were considered to be the key potential genes involved in the abiotic stress mechanisms in D. salina . Phylogenetic analysis indicated that the 17 DsMAPKKKs could be classified into three subfamilies. Conserved motif analysis showed that the 17 DsMAPKKKs had typical domains and had some specific domains. Interestingly, one of the DsMAPKKK genes had both a GAF domain and a PAS domain, while no MAPKKK genes exhibited these two domains in other plant species, thereby representing a source of adaptive plasticity that is specific to D. salina . Furthermore, we used the STRING database to predict the interaction network and the DsMAPKKK9-DsMEK1, DsMAPKKK12-DsMEK2 interaction pathways were confirmed by the Y2H assay, which implies that these interaction pathways may regulate cytokinesis in D. salina. In conclusion, homologous mapping and the Y2H assay validated two MAPKKK-MAPKK cascade pathways in D. salina . These data further promote our understanding of the intricate transcriptional control of MAPKKK-MAPKK genes and provide pivotal candidate genes for the protein interaction network in D. salina.