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Serine and threonine residues of plant STN 7 kinase are differentially phosphorylated upon changing light conditions and specifically influence the activity and stability of the kinase
Author(s) -
Trotta Andrea,
Suorsa Marjaana,
Rantala Marjaana,
Lundin Björn,
Aro EvaMari
Publication year - 2016
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.13213
Subject(s) - phosphorylation , protein phosphorylation , serine , threonine , kinase , biochemistry , phosphorylation cascade , protein kinase a , biology , microbiology and biotechnology , light intensity , chemistry , physics , optics
Summary STN 7 kinase catalyzes the phosphorylation of the globally most common membrane proteins, the light‐harvesting complex II ( LHCII ) in plant chloroplasts. STN 7 itself possesses one serine (Ser) and two threonine (Thr) phosphosites. We show that phosphorylation of the Thr residues protects STN 7 against degradation in darkness, low light and red light, whereas increasing light intensity and far red illumination decrease phosphorylation and induce STN 7 degradation. Ser phosphorylation, in turn, occurs under red and low intensity white light, coinciding with the client protein ( LHCII ) phosphorylation. Through analysis of the counteracting LHCII phosphatase mutant tap38 / pph1 , we show that Ser phosphorylation and activation of the STN 7 kinase for subsequent LHCII phosphorylation are heavily affected by pre‐illumination conditions. Transitions between the three activity states of the STN 7 kinase (deactivated in darkness and far red light, activated in low and red light, inhibited in high light) are shown to modulate the phosphorylation of the STN 7 Ser and Thr residues independently of each other. Such dynamic regulation of STN 7 kinase phosphorylation is crucial for plant growth and environmental acclimation.