Genome-wide identification and expression pattern analysis under abiotic stress of mitogen-activated protein kinase genes in Pyropia yezoensis

The mitogen-activated protein kinase (MAPK) cascade is composed of three hierarchically organized protein kinases (MAP kinase kinase kinases, MAP kinase kinases, and MAPKs) and plays a vital role in regulating developmental processes and stress responses in plants. Pyropia yezoensis belongs to the old Rhodophyta and grows in intertidal zones. Although MAPKs have been well studied in some model plants, there is little information available concerning the P. yezoensis MAPK gene family and their roles in adaptation to intertidal environments. In this study, we identified 15 MAPKs from P. yezoensis (PyMAPKs) based on genome-wide analysis of the omics database. Conserved motif analysis indicated that all PyMAPKs had typical protein kinase domains; however, in addition to TEY/TDY activation loop motifs, some new types of activation loop motifs were identified: TTY, TAY, TQY, TSH, TAH, and TQA. Phylogenetic analysis showed that, with other red algae, PyMAPKs formed three groups independent from green plants, indicating that red algae retained older MAPK types than green plants. Transcriptomic analysis suggested that members of the PyMAPK gene family were involved in response to dehydration/rehydration and temperature stress and showed differential expression patterns. This work represents the first complete inventory of MAPKs from red algae and could help elucidate the mechanisms involving these proteins in P. yezoensis responses to abiotic stress.