Overexpression of thioredoxin m in tobacco chloroplasts inhibits the protein kinase STN7 and alters photosynthetic performance

Date

2019

Director

Publisher

Oxford University Press
Acceso abierto / Sarbide irekia
Artículo / Artikulua
Versión publicada / Argitaratu den bertsioa

Project identifier

ES/1PE/AGL2016-79868
Impacto

Abstract

The activity of the protein kinase STN7, involved in phosphorylation of the light-harvesting complex II (LHCII) proteins, has been reported as being co-operatively regulated by the redox state of the plastoquinone pool and the ferredoxin–thioredoxin (Trx) system. The present study aims to investigate the role of plastid Trxs in STN7 regulation and their impact on photosynthesis. For this purpose, tobacco plants overexpressing Trx f or m from the plastid genome were characterized, demonstrating that only Trx m overexpression was associated with a complete loss of LHCII phosphorylation that did not correlate with decreased STN7 levels. The absence of phosphorylation in Trx m-overexpressing plants impeded migration of LHCII from PSII to PSI, with the concomitant loss of PSI–LHCII complex formation. Consequently, the thylakoid ultrastructure was altered, showing reduced grana stacking. Moreover, the electron transport rate was negatively affected, showing an impact on energy-demanding processes such as the Rubisco maximum carboxylation capacity and ribulose 1,5-bisphosphate regeneration rate values, which caused a strong depletion in net photosynthetic rates. Finally, tobacco plants overexpressing a Trx m mutant lacking the reactive redox site showed equivalent physiological performance to the wild type, indicating that the overexpressed Trx m deactivates STN7 in a redox-dependent way.

Description

Keywords

LHCII phosphorylation, Nicotiana tabacum, Photosynthesis, Protein complex, Thioredoxin, Thylakoid membrane

Department

IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua

Faculty/School

Degree

Doctorate program

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© The Author(s) 2018. This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

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