Acts as a negative regulator in the ethylene response pathway (PubMed:8431946). Phosphorylates the cytosolic C-terminal domain of EIN2, preventing the signaling in the absence of ethylene (PubMed:23132950). Interacts with C24:1-ceramide upon hypoxic conditions (e.g. submergences) to in turn regulate EIN2 endoplasmic reticulum (ER)-to-nucleus translocation and EIN3 stabilization (PubMed:25822663). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Kinase activity is inhibited by C24:1-ceramide during hypoxia (e.g. submergences). Interacts with EIN2 (via C-terminus). Expressed in both seedlings and adult plants. Mutants display ethylene-treated phenotypes, resulting in plants with small, unexpanded leaves and whose seed cotyledon growth is impaired. Belongs to the protein kinase superfamily. TKL Ser/Thr protein kinase family. RAF subfamily.