MKK3-MPK6 module plays an important role in the jasmonate signal transduction pathway through the negative regulation of MYC2/JIN1 expression. Activates by phosphorylation the downstream MPK6, MPK7 and MPK8. MKK3-MPK7 module acts as a positive regulator of PR1 gene expression. MKK3-MPK8 module negatively regulates ROS accumulation through controlling expression of the RBOHD gene. Component of the abscisic acid (ABA) signaling pathway that may act as ABA signal transducer in the context of abiotic stresses. Activator of the C group MAP kinases. Activates MPK7 in response to ABA (PubMed:25720833). Mitogen-activated protein kinase (MAPK) that is specifically regulated by MAPKKK20 and mediates signaling that regulates cortical microtubule functions (PubMed:28848569). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Interacts with MPK1, MPK2 and MPK7 (PubMed:17933903, PubMed:19513235, PubMed:25680457). Interacts with P.syringae type III effector HopF2 (PubMed:20571112). Interacts with MPK14 (PubMed:19513235). Binds to MAPKKK17 and MAPKKK18 (PubMed:25720833, PubMed:25680457). Binds to MAPKKK20 (PubMed:28848569, PubMed:30081740). Mostly expressed in leaves, and, to a lower extent, in roots, seedlings, flower buds, flowers and siliques. By Pseudomonas syringae pv tomato strain DC3000 infection. Phosphorylation at Ser-235 and Thr-241 by MAP kinase kinase kinases positively regulates kinase activity (Probable). Phosphorylated by MAPKKK20 (PubMed:28848569). More sensitive to Pseudomonas syringae pv. tomato DC3000 infection (PubMed:17933903). Hypersensitivity to abscisic acid (ABA) in germination and root elongation (PubMed:25720833). Short roots with abnormal twisting (e.g. leftward skewing) in media containing microtubule-disrupting drugs (e.g. oryzalin) (PubMed:28848569). Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. MAP kinase kinase subfamily.