Cross-talk between calcium signalling and protein phosphorylation at the thylakoid

Abstract

The role of protein phosphorylation for adjusting chloroplast functions to changing environmental needs is well established, whereas calcium signalling in the chloroplast is only recently becoming appreciated. The work presented here explores the potential cross-talk between calcium signalling and protein phosphorylation in chloroplasts and provides the first evidence for targets of calcium-dependent protein phosphorylation at the thylakoid membrane. Thylakoid proteins were screened for calcium-dependent phosphorylation by 2D gel electrophoresis combined with phospho-specific labelling and PsaN, CAS, and VAR1, among other proteins, were identified repeatedly by mass spectrometry. Subsequently their calcium-dependent phosphorylation was confirmed in kinase assays using the purified proteins and chloroplast extracts. This is the first report on the protein targets of calcium-dependent phosphorylation of thylakoid proteins and provides ground for further studies in this direction.

Calcium-dependent regulation of cyclic photosynthetic electron transfer by a CAS, ANR1, and PGRL1 complex

“…Loss of CAS function has been reported to impair stimulus-induced changes in cytoplasmic Ca 2+ dynamics (10), and we report here that CEF activity of the ami-RNA-anr1 and RNAi-cas-205 lines can also be restored by elevated Ca 2+ concentrations, although to a different degree. In particular, we propose that the calcium-binding protein CAS (28) could be directly involved in transducing changes in Ca 2+ concentration in the cytosol into chloroplast Ca 2+ responses (29), leading to changes in CEF activity by a still unknown mechanism. Indeed, elevation of external Ca 2+ totally restores CEF in RNAi-cas lines, and CAS-and Ca 2+ -dependent regulation of CEF coincides with the regulation of LHCSR3 expression.…”

The Antarctic Psychrophile Chlamydomonas sp. UWO 241 Preferentially Phosphorylates a Photosystem I-Cytochrome b6/f Supercomplex

“…All values represent means 6 SE from nine to 13 measurements in three independent experiments. All measurements were performed at the corresponding growth temperatures for UWO 241 (5˚C) and SAG 49.72 (25˚C (Stael et al, 2012). The phosphorylation state of thylakoid membranes is the net effect of the combined rates of protein phosphorylation by thylakoid kinases such as the STT7/STT8 kinases versus the rates of dephosphorylation by thylakoid protein phosphatases such as PPH1/TAP38 (Rochaix, 2011).…”

Signaling with Ions: The Keystone for Apical Cell Growth and Morphogenesis in Pollen Tubes

“…Some GLRs are expressed in endomembranes and may participate in Ca 2+ signaling (Teardo et al, 2011. Experimental evidence also is suggestive of a role for the Arabidopsis mitochondrial channel uniporter regulator MICU, a Ca 2+ -binding protein that modulates the mitochondrial Ca 2+ accumulation (Stael et al, 2012). Interestingly, MICU is expressed in PTs (Wang et al, 2008b).…”