Involved in innate immunity. Required for the expression of defense-related genes PR1A, LOX2 and CHS1 upon biotic stresses. Required for basal resistance to the fungal blast (M.grisea), bacterial blight (X.oryzae pv. oryzae, Xoo) and the herbivorous insect brown planthopper (N.lugens, BPH). May be involved in several defense signaling pathways. Involved in the promotion of seed germination. Required for the expression of alpha-amylase genes during seed germination (By similarity). Involved in resistance against the herbivorous insect brown planthopper (N.lugens, BPH). Member of the BPH3 (BPH resistance locus 3) cluster which contains LECRK1, LECRK2 and LECRK3 (PubMed:25485617). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.