STN7 (serine/threonine protein kinase) (EC=2.7.11.1) in Arabidopsis thaliana, and its Stt7 homologue in Chlamydomonas reinhardtii, is required for LHCII phosphorylation and for state transitions. The loss of this thylakoid-associated kinase blocked stn7 (stt7)-deficient mutants in state 1. Alternative names: Protein STATE TRANSITION 7, Stt7 homolog.