Refereed journal article or data article (A1)
Crosstalk between chloroplast thioredoxin systems in regulation of photosynthesis
List of Authors: Nikkanen L, Toivola J, Rintamaki E
Publisher: WILEY-BLACKWELL
Publication year: 2016
Journal: Plant, Cell and Environment
Journal name in source: PLANT CELL AND ENVIRONMENT
Journal acronym: PLANT CELL ENVIRON
Volume number: 39
Issue number: 8
Start page: 1691
End page: 1705
Number of pages: 15
ISSN: 0140-7791
eISSN: 1365-3040
DOI: http://dx.doi.org/10.1111/pce.12718
Abstract
Thioredoxins (TRXs) mediate light-dependent activation of primary photosynthetic reactions in plant chloroplasts by reducing disulphide bridges in redox-regulated enzymes. Of the two plastid TRX systems, the ferredoxin-TRX system consists of ferredoxin-thioredoxin reductase (FTR) and multiple TRXs, while the NADPH-dependent thioredoxin reductase (NTRC) contains a complete TRX system in a single polypeptide. Using Arabidopsis plants overexpressing or lacking a functional NTRC, we have investigated the redundancy and interaction between the NTRC and Fd-TRX systems in regulation of photosynthesis in vivo. Overexpression of NTRC raised the CO2 fixation rate and lowered non-photochemical quenching and acceptor side limitation of PSI in low light conditions by enhancing the activation of chloroplast ATP synthase and TRX-regulated enzymes in Calvin-Benson cycle (CBC). Overexpression of NTRC with an inactivated NTR or TRX domain partly recovered the phenotype of knockout plants, suggesting crosstalk between the plastid TRX systems. NTRC interacted in planta with fructose-1,6-bisphosphatase, phosphoribulokinase and CF1 gamma subunit of the ATP synthase and with several chloroplast TRXs. These findings indicate that NTRC-mediated regulation of the CBC and ATP synthesis occurs both directly and through interaction with the ferredoxin-TRX system and is crucial when availability of light is limiting photosynthesis.
Thioredoxins (TRXs) mediate light-dependent activation of primary photosynthetic reactions in plant chloroplasts by reducing disulphide bridges in redox-regulated enzymes. Of the two plastid TRX systems, the ferredoxin-TRX system consists of ferredoxin-thioredoxin reductase (FTR) and multiple TRXs, while the NADPH-dependent thioredoxin reductase (NTRC) contains a complete TRX system in a single polypeptide. Using Arabidopsis plants overexpressing or lacking a functional NTRC, we have investigated the redundancy and interaction between the NTRC and Fd-TRX systems in regulation of photosynthesis in vivo. Overexpression of NTRC raised the CO2 fixation rate and lowered non-photochemical quenching and acceptor side limitation of PSI in low light conditions by enhancing the activation of chloroplast ATP synthase and TRX-regulated enzymes in Calvin-Benson cycle (CBC). Overexpression of NTRC with an inactivated NTR or TRX domain partly recovered the phenotype of knockout plants, suggesting crosstalk between the plastid TRX systems. NTRC interacted in planta with fructose-1,6-bisphosphatase, phosphoribulokinase and CF1 gamma subunit of the ATP synthase and with several chloroplast TRXs. These findings indicate that NTRC-mediated regulation of the CBC and ATP synthesis occurs both directly and through interaction with the ferredoxin-TRX system and is crucial when availability of light is limiting photosynthesis.
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