Ribosomal S6 kinase 1/2 (S6K1/2) involved in TOR signaling pathway, in osmotic stress response. Activated by PDK1 and repressed during osmotic stress. Expressed in all tissues, especially during high metabolic activity in growing buds, root tips, leaf margins and germinating seeds. Alternative names: AtPK1/AtPK6 S6K1), AtPK2/AtPK19 (S6K2).?