Catalytic domain of the Serine/Threonine Kinases, Plant TDY Mitogen-Activated Protein Kinases
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. Plant MAPKs are typed based on the conserved phosphorylation motif present in the activation loop, TEY and TDY. This subfamily represents the TDY subtype and is composed of Group D plant MAPKs including Arabidopsis thaliana MPK18 (AtMPK18), Oryza sativa Blast- and Wound-induced MAPK1 (OsBWMK1), OsWJUMK1 (Wound- and JA-Uninducible MAPK1), Zea mays MPK6, and the Medicago sativa TDY1 gene product. OsBWMK1 enhances resistance to pathogenic infections. It mediates stress-activated defense responses by activating a transcription factor that affects the expression of stress-related genes. AtMPK18 is involved in microtubule-related functions. In plants, MAPKs are associated with physiological, developmental, hormonal, and stress responses. Some plants show numerous gene duplications of MAPKs; Arabidopsis thaliana harbors at least 20 MAPKs, named AtMPK1-20 while Oryza sativa contains at least 17 MAPKs. Arabidopsis thaliana contains more TEY-type MAPKs than TDY-type, whereas the reverse is true for Oryza sativa. The TDY MAPK subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.