Working day and night: plastid casein kinase 2 catalyses phosphorylation of target proteins with diverse functions in light and dark-adapted plastids

ABSTRACT: Casein kinase 2 is a ubiquitous protein kinase that has puzzled researchers for several decades because of its pleiotropic activity. Here we set out to identify the _in vivo_ targets of plastid casein kinase 2 (pCK2) in _Arabidopsis thaliana_. Survey phosphoproteome analyses were combined with targeted analyses with wildtype and _pck2_ knockdown mutants to identify potential pCK2 targets by their decreased phosphorylation state in the mutant. To validate potential substrates, we complemented the _pck2_ knockdown line with TAP-tagged pCK2 and found it to restore growth parameters as well as many -but not all- of the putative pCK2-dependent phosphorylation events. We further performed a targeted analysis at the end-of-night to increase the specificity of target protein identification. This analysis confirmed light-independent phosphorylation of some pCK2 target proteins. Based on the aforementioned data, we define a set of _in vivo_ pCK2-targets that span different chloroplast functions such as metabolism, transcription, translation and photosynthesis. The pleiotropy of CK2 functions is also manifested by altered state transition kinetics during short-term-acclimation and significant alterations in the mutant metabolism supporting its crosstalk with photosynthetic regulation. Thus, our data expand our understanding on chloroplast phosphorylation networks and provide novel insights into kinase crosstalk in the biogenic regulation of chloroplast functions.

INSTRUMENT(S): LTQ Orbitrap Velos

ORGANISM(S): Arabidopsis Thaliana (mouse-ear Cress)

TISSUE(S): Plant Cell, Leaf

SUBMITTER: Sacha Baginsky  

LAB HEAD: Prof. Dr. Sacha Baginsky

PROVIDER: PXD014930 | Pride | 2021-07-19

REPOSITORIES: Pride