Characterization of a nonphotochemical quenching-deficient Arabidopsis mutant possessing an intact PsbS protein, xanthophyll cycle and lumen acidification

Abstract

Arabidopsis thaliana plants grown from ethyl methane sulfonate-treated seeds were screened for so-called que mutants, which are affected in non-photochemical energy quenching. Based on video imaging of chlorophyll fluorescence an energy dissipation mutant, que1, was identified, isolated and characterized. Similar to the npq mutants, the que1 mutant showed a drastically reduced capacity for pH-dependent energy dissipation, qE, but without affecting the Delta pH-dependent conformational changes at 535 nm (DeltaA (535)), which have been supposed to be obligatorily correlated with qE and to reflect pH-regulated binding of zeaxanthin to the PsbS protein. Western blot and DNA sequence analysis revealed that neither a reduced expression of the PsbS protein nor a mutation in the PsbS gene was responsible for the missing qE in que1. Measurements of 9-aminoacridine fluorescence quenching showed that the acidification of the thylakoid lumen was also not affected in the mutant. Furthermore, que1 was able to convert violaxanthin to zeaxanthin. However, unusual characteristics of zeaxanthin formation in the mutant pointed at an altered availability of violaxanthin for de-epoxidation. This was further accompanied by a decrease of the photochemical quenching of chlorophyll fluorescence (qP), an increase of the portion of oxidized P700 and a reduction of the electron transport rate. These characteristics indicate changes in the organization of the thylakoid membrane that affect linear electron transport (but not lumen acidification) and the formation of energy dissipation in photosystem II. Preliminary genetic analysis revealed that the phenotype of que1 is related to two different mutations, mapped to the lower arms of chromosomes 1 and 4.

The Zeaxanthin-Independent and Zeaxanthin-Dependent qE Components of Nonphotochemical Quenching Involve Common Conformational Changes within the Photosystem II Antenna in Arabidopsis

“…7A). The broken correlation between DA 535 and qE in lut2npq2 suggests that the absorption change does not directly reflect the formation of a quenching species, consistent with a recent report (Kalituho et al, 2006a). A similar conclusion can be drawn from the appearance of the large transient in DA 535 in the kolhcb6 mutant that was not associated with a similar transient in NPQ.…”

Kinetic and Spectral Resolution of Multiple Nonphotochemical Quenching Components in Arabidopsis Leaves

“…There exist a number of literature reviews on the subject (Demmig-Adams and Adams, 1992;Horton et al, 1996;Ruban, 1999, 2005;Niyogi, 1999Niyogi, , 2000Mü ller et al, 2001;Golan et al, 2004;Krause and Jahns, 2004). Chlorophyll (Chl) fluorescence, and in particular pulse amplitude-modulated (PAM) fluorometry as introduced by Schreiber et al (1986), has become by far the dominant technique to measure NPQ in leaves, chloroplasts, and intact microorganisms (Krause and Weis, 1991;Govindjee, 1995;Maxwell and Johnson, 2000;Krause and Jahns, 2003;Schreiber, 2004), more recently often combined with specific NPQ mutant studies Kalituho et al, 2006Kalituho et al, , 2007Dall'Osto et al, 2007). In this technique, periodic saturating light pulses are applied, superimposed on the continuous actinic irradiation applied to induce NPQ, in order to transiently close the PSII reaction centers (RCs).…”

The Transiently Generated Nonphotochemical Quenching of Excitation Energy in Arabidopsis Leaves Is Modulated by Zeaxanthin

“…This process is controlled by the synergistic action of the lumen pH, xanthophyll binding, and conformational changes in the antenna of PSII (Horton et al, 2000). Generation of the maximum qE essentially requires a lumen pH below 6 (Munekage et al, 2001;Jahns et al, 2002), de-epoxidized xanthophylls (Niyogi et al, 1998), the PsbS protein (Li et al, 2000), and other antenna proteins of PSII Kalituho et al, 2006). qE is strictly regulated by the pH in the thylakoid lumen and generated within 10 min of illumination at saturating light intensities.…”