The major thylakoid protein kinases STN7 and STN8 revisited: effects of altered STN8 levels and regulatory specificities of the STN kinases
Thylakoid phosphorylation is predominantly mediated by the protein kinases STN7 and STN8. While STN7 primarily catalyzes LHCII phosphorylation, which enables LHCII to migrate from photosystem (PS) II to PSI, STN8 mainly phosphorylates PSII core proteins. The reversible phosphorylation of PSII core p...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2013-10-01
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| Series: | Frontiers in Plant Science |
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| Online Access: | http://journal.frontiersin.org/Journal/10.3389/fpls.2013.00417/full |
| _version_ | 1811263196138307584 |
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| author | Tobias eWunder Wenteng eXu Qiuping eLiu Gerhard eWanner Dario eLeister Dario eLeister Mathias ePribil Mathias ePribil |
| author_facet | Tobias eWunder Wenteng eXu Qiuping eLiu Gerhard eWanner Dario eLeister Dario eLeister Mathias ePribil Mathias ePribil |
| author_sort | Tobias eWunder |
| collection | DOAJ |
| description | Thylakoid phosphorylation is predominantly mediated by the protein kinases STN7 and STN8. While STN7 primarily catalyzes LHCII phosphorylation, which enables LHCII to migrate from photosystem (PS) II to PSI, STN8 mainly phosphorylates PSII core proteins. The reversible phosphorylation of PSII core proteins is thought to regulate the PSII repair cycle and PSII supercomplex stability, and play a role in modulating the folding of thylakoid membranes. Earlier studies clearly demonstrated a considerable substrate overlap between the two STN kinases, raising the possibility of a balanced interdependence between them at either the protein or activity level. Here, we show that such an interdependence of the STN kinases on protein level does not seem to exist as neither knock-out nor overexpression of STN7 or STN8 affects accumulation of the other. STN7 and STN8 are both shown to be integral thylakoid proteins that form part of molecular supercomplexes, but exhibit different spatial distributions and are subject to different modes of regulation. Evidence is presented for the existence of a second redox-sensitive motif in STN7, which seems to be targeted by thioredoxin f. Effects of altered STN8 levels on PSII core phosphorylation, supercomplex formation, photosynthetic performance and thylakoid ultrastructure were analyzed in Arabidopsis thaliana using STN8-overexpressing plants (oeSTN8). In general, oeSTN8 plants were less sensitive to intense light and exhibited changes in thylakoid ultrastructure, with grana stacks containing more layers and reduced amounts of PSII supercomplexes. Hence, we conclude that STN8 acts in an amount-dependent manner similar to what was shown for STN7 in previous studies. However, the modes of regulation of the STN kinases appear to differ significantly. |
| first_indexed | 2024-04-12T19:40:19Z |
| format | Article |
| id | doaj.art-fc821da088e54386878cd30984005348 |
| institution | Directory Open Access Journal |
| issn | 1664-462X |
| language | English |
| last_indexed | 2024-04-12T19:40:19Z |
| publishDate | 2013-10-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Plant Science |
| spelling | doaj.art-fc821da088e54386878cd309840053482022-12-22T03:19:06ZengFrontiers Media S.A.Frontiers in Plant Science1664-462X2013-10-01410.3389/fpls.2013.0041765791The major thylakoid protein kinases STN7 and STN8 revisited: effects of altered STN8 levels and regulatory specificities of the STN kinasesTobias eWunder0Wenteng eXu1Qiuping eLiu2Gerhard eWanner3Dario eLeister4Dario eLeister5Mathias ePribil6Mathias ePribil7LMU MunichLMU MunichLMU MunichLMU MunichLMU MunichPhotoLab Trentino - a joint initiative of the University of Trento (Centre for Integrative Biology) & the Edmund Mach Foundation (Research and Innovation Centre)LMU MunichLMU MunichThylakoid phosphorylation is predominantly mediated by the protein kinases STN7 and STN8. While STN7 primarily catalyzes LHCII phosphorylation, which enables LHCII to migrate from photosystem (PS) II to PSI, STN8 mainly phosphorylates PSII core proteins. The reversible phosphorylation of PSII core proteins is thought to regulate the PSII repair cycle and PSII supercomplex stability, and play a role in modulating the folding of thylakoid membranes. Earlier studies clearly demonstrated a considerable substrate overlap between the two STN kinases, raising the possibility of a balanced interdependence between them at either the protein or activity level. Here, we show that such an interdependence of the STN kinases on protein level does not seem to exist as neither knock-out nor overexpression of STN7 or STN8 affects accumulation of the other. STN7 and STN8 are both shown to be integral thylakoid proteins that form part of molecular supercomplexes, but exhibit different spatial distributions and are subject to different modes of regulation. Evidence is presented for the existence of a second redox-sensitive motif in STN7, which seems to be targeted by thioredoxin f. Effects of altered STN8 levels on PSII core phosphorylation, supercomplex formation, photosynthetic performance and thylakoid ultrastructure were analyzed in Arabidopsis thaliana using STN8-overexpressing plants (oeSTN8). In general, oeSTN8 plants were less sensitive to intense light and exhibited changes in thylakoid ultrastructure, with grana stacks containing more layers and reduced amounts of PSII supercomplexes. Hence, we conclude that STN8 acts in an amount-dependent manner similar to what was shown for STN7 in previous studies. However, the modes of regulation of the STN kinases appear to differ significantly.http://journal.frontiersin.org/Journal/10.3389/fpls.2013.00417/fullProtein phosphorylationchloroplastredoxPSII supercomplexesSTN kinasesthylakoid ultrastructure |
| spellingShingle | Tobias eWunder Wenteng eXu Qiuping eLiu Gerhard eWanner Dario eLeister Dario eLeister Mathias ePribil Mathias ePribil The major thylakoid protein kinases STN7 and STN8 revisited: effects of altered STN8 levels and regulatory specificities of the STN kinases Frontiers in Plant Science Protein phosphorylation chloroplast redox PSII supercomplexes STN kinases thylakoid ultrastructure |
| title | The major thylakoid protein kinases STN7 and STN8 revisited: effects of altered STN8 levels and regulatory specificities of the STN kinases |
| title_full | The major thylakoid protein kinases STN7 and STN8 revisited: effects of altered STN8 levels and regulatory specificities of the STN kinases |
| title_fullStr | The major thylakoid protein kinases STN7 and STN8 revisited: effects of altered STN8 levels and regulatory specificities of the STN kinases |
| title_full_unstemmed | The major thylakoid protein kinases STN7 and STN8 revisited: effects of altered STN8 levels and regulatory specificities of the STN kinases |
| title_short | The major thylakoid protein kinases STN7 and STN8 revisited: effects of altered STN8 levels and regulatory specificities of the STN kinases |
| title_sort | major thylakoid protein kinases stn7 and stn8 revisited effects of altered stn8 levels and regulatory specificities of the stn kinases |
| topic | Protein phosphorylation chloroplast redox PSII supercomplexes STN kinases thylakoid ultrastructure |
| url | http://journal.frontiersin.org/Journal/10.3389/fpls.2013.00417/full |
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