Rubisco Activase -- a Typical AAA+ Protein With Unique Features, And, PIFI -- a Novel Chloroplast Protein Functioning in Chlororespiration
A novel Arabidopsis chloroplast protein, named PIFI, with a similar C-extension as activase was identified as functioning in chlororespiration and possibly cyclic electron transport by reverse genetics. In a pifi mutant, which possesses an intact NDH complex, NDH-mediated dark reduction of plastoquinone was disrupted as indicated by its post-illumination fluorescence kinetics. The pifi mutant exhibited low capacity for thermal dissipation and a low oxidation level of the PSI reaction center, but similar electron transport efficiency of PSII as that of wild type, suggesting an impaired cyclic electron flow around PSI in the mutant. The PIFI protein is dispensable under standard growth conditions but important in protecting plants from photoinhibition and mild heat stress.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign