High impact information on NPQ4

• Here we show that the gene encoding PsbS, an intrinsic chlorophyll-binding protein of photosystem II, is necessary for nonphotochemical quenching but not for efficient light harvesting and photosynthesis [1].
• The high levels of zeaxanthin in npq2 affected the kinetics of induction and relaxation but not the extent of nonphotochemical quenching [2].
• The npq1 mutant exhibited greatly reduced nonphotochemical quenching, demonstrating that violaxanthin deepoxidation is required for the bulk of rapidly reversible nonphotochemical quenching in Arabidopsis [2].
• To dissect the role of xanthophylls in photoprotective energy dissipation in vivo, we isolated Arabidopsis xanthophyll cycle mutants by screening for altered nonphotochemical quenching of chlorophyll fluorescence [2].
• A zeaxanthin-independent nonphotochemical quenching mechanism localized in the photosystem II core complex [3].

Biological context of NPQ4

• Diploid Arabidopsis plants containing two psbS gene copies (wild-type), one psbS gene (npq4-1/NPQ4 heterozygote), and no psbS gene (npq4-1/npq4-1 homozygote) were compared [4].
• The npq4 mutant, which possesses a normal violaxanthin cycle but has a limited capacity of quenching singlet excited chlorophylls, was rather tolerant to lipid peroxidation [5].
• Molecular and global time-resolved analysis of a psbS gene dosage effect on pH- and xanthophyll cycle-dependent nonphotochemical quenching in photosystem II [4].
• The NPQ-deficient phenotype was meiotically transmissible as a semidominant trait and mapped near marker T27K12 on chromosome 1 [6].
• We describe the properties of npq4-9, a new mutant of Arabidopsis thaliana (L.) Heynh. with reduced nonphotochemical quenching (NPQ) capacity that possesses a single amino acid substitution in the PsbS gene encoding PSII-S, a ubiquitous pigment-binding protein associated with photosystem II (PSII) of higher plants [7].

Anatomical context of NPQ4

• We conclude that at least two major factors determine the quenching of chlorophyll fluorescence in Lhcb proteins, i.e., intrasubunit conformational change and intersubunit interactions within the lipid membranes, and that these processes are both important in the photoprotection mechanism of nonphotochemical quenching in vivo [8].
• Nonphotochemical quenching (NPQ) of excitation energy, which protects higher plant photosynthetic machinery from photodamage, is triggered by acidification of the thylakoid lumen as a result of light-induced proton pumping, which also drives the synthesis of ATP [9].

Associations of NPQ4 with chemical compounds

• Xanthophyll cycle-dependent nonphotochemical quenching in Photosystem II: Mechanistic insights gained from Arabidopsis thaliana L. mutants that lack violaxanthin deepoxidase activity and/or lutein [10].
• However, use of the violaxanthin de-epoxidase inhibitor dithiothreitol indicated that a zeaxanthin-dependent component of NPQ was specifically reduced in the mutant [6].

Analytical, diagnostic and therapeutic context of NPQ4

• Pulse-modulation fluorometry was employed to characterize one line (denoted Lsr1(-)) that exhibited an approximately 50% reduction in NPQ compared to the wild type (WT) [6].

References