Regulates flowering time by modulating the photoperiod pathway. Possesses kinase activity in vitro. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Expressed with a circadian rhythm showing a peak before dawn. Autophosphorylated. Plants display early flowering and altered expression of genes involved in the photoperiod flowering pathway, such as ELF4, TOC1, CO and FT. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. WNK subfamily. Was named WNK/'with no lysine(K)' because key residues for catalysis, including the lysine involved in ATP binding, are either not conserved or differ compared to the residues described in other kinase family proteins.