Structure And Activation Mechanism Of Receptor-like Kinase RGIs In Arabidopsis

The largest class of receptor-like protein kinases in plants is the leucine-rich repeat receptor like kinase(LRR-RLKs),which play important roles in plant development and stress response.Each LRR-RLK consists of three functional domains:a leucine-rich repeat ectodomain that senses extracellular signal stimuli,a transmembrane region that anchors the protein within a membrane and an intracellular kinase domain that transmits signals to downstream proteins through phosphorylation.The extracellular leucine-rich repeat can sense multiple ligands,such as hormones and peptides,and then recruit the co-receptor to form heterodimers that activate each other to transmit extracellular signals downstream.Root meristem growth factor 1(RGF1),a sulfated peptide hormone,controls the stability of PLETHORA 1/2,which maintains stem cell growth.RGIs(Root meristem growth factor 1 INSENSITIVE),the receptors of RGF1,participates in the RGF-PLT signaling pathway and regulates the growth and development of plant roots.Here,we purified high concentration and high purity recombinant proteins from E.coli through protein cloning,expression,purification and related experimental techniques.We obtained the crystals of RGI3-KD and the crystal structure of RGI3-KD is in an activated conformation.In addition,we found that dephosphorylated RGI3 undergoes negligible autophosphorylation in vitro,but could transphosphorylate with its co-receptor BAK1.Hence,we propose that RGIs and BAK1 are principally activated via transphosphorylation dependent on the RGF ligand induced heterodimerization,and this model is very similar to the BL-dependent BRI1-BAK1 activation.