
TY  - JOUR
A1  - Govindjee, 
A1  - Spilotro, Paul 
T1  - An <emph type="2">Arabidopsis thaliana</emph> mutant, altered in the &#947;-subunit of ATP synthase, has a different pattern of intensity-dependent changes in non-photochemical quenching and kinetics of the <emph type="2">P</emph>-to-<emph type="2">S</emph> fluorescence decay
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 2002
VL  - 29
IS  - 4
SP  - 425
EP  - 434
KW  - ATP synthase, chlorophyll a fluorescence induction, non-photochemical quenching, pH gradient, photoinhibition, 515&#8211;518-nm absorbance changes.
UR  - https://doi.org/10.1071/PP01136 
N2  - A major photoprotective mechanism that plants employ against excess light involves interplay between the xanthophyll cycle and the accumulation of protons. Using mutants in the xanthophyll cycle, the roles of violaxanthin, antheraxanthin and zeaxanthin have already been well established. In this paper, we present data on intact leaves of a mutant &#91;coupling factor quick recovery mutant (cfq); atpC1:E244K&#93; of Arabidopsis thaliana that we expected, based on 515-nm absorbance changes (Gabrys et al. 1994, Plant Physiology 104, 769&#8211;776), to have differences in light-induced &#916;pH. The significance of this paper is: (i) it is the first study of the photoprotective energy dissipation involving a mutant of the pH gradient; it establishes that protons play an important role in the pattern of non-photochemical quenching (NPQ) of chlorophyll (Chl) a fluorescence; and (ii) differences between the cfq and the wild type (wt) are observed only under subsaturating light intensities, and are strongest in the initial few minutes of the induction period. Our results on light-intensity dependent Chl* a fluorescence transients (the Kautsky effect), and on NPQ of Chl a fluorescence, at 50&#8211;250 &#956;mol photons m&#8211;2 s&#8211;1 demonstrate: (i) the &#8216;P-to-S&#8217; (or &#8216;T&#8217;) decay, known to be related to &#91;H+&#93; (Briantais et al. 1979, Biochimica et Biophysica Acta 548, 128&#8211;138), is slowed in the mutant; and (ii) the pattern of NPQ kinetics is different in the initial 100 s &#8212; in the wt leaves, there is a marked rise and decline, and in the cfq mutant, there is a slowed rise. These differences are absent at 750 &#956;mol photons m&#8211;2 s&#8211;1. Pre-illumination and nigericin (an uncoupler that dissipates the proton gradient) treatment of the cfq mutant, which has lower &#916;pH relative to wild type, confirm the conclusion that protons play an important role in the quenching of Chl a fluorescence. 
ER  -

