Disease relevance of NPQ1

• The corresponding increases in non-photochemical quenching and greater rates of non-stomatal water loss from these regions, as well as the partial reversal of low PhiPSII by increasing the ambient CO2 concentration, suggests that localized water stress and reduced stomatal conductance contributed to the inhibition of photosynthesis [1].

High impact information on NPQ1

• The npq1 mutants are unable to convert violaxanthin to zeaxanthin in excessive light, whereas the npq2 mutants accumulate zeaxanthin constitutively [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].
• Genetic mapping, DNA sequencing, and complementation of npq1 demonstrated that this mutation affects the structural gene encoding violaxanthin deepoxidase [2].
• Lipid peroxidation was more pronounced in npq1 compared with the wild type, as measured by chlorophyll thermoluminescence, ethane production, and the total hydroperoxy fatty acids content [3].
• Prolonged exposure of whole plants to bright light resulted in a limited photoinhibition of photosystem II in both npq1 and wild-type leaves, although CO(2) fixation and the linear electron transport in npq1 plants were reduced substantially [3].

Biological context of NPQ1

• LHC II protein phosphorylation in leaves of Arabidopsis thaliana mutants deficient in non-photochemical quenching [4].
• Lipid peroxidation was amplified markedly under chilling stress, and photooxidative damage ultimately resulted in leaf bleaching and tissue necrosis in npq1 [3].
• At low light intensity, chlorophyll fluorescence induction kinetics is close to those found in wild type, but non-photochemical quenching strongly increases with increasing actinic light intensity resulting in steady state fluorescence levels of about 60% of the minimal dark fluorescence [5].
• This was in contrast to the npq1 single mutant that showed only slight deviations from the wild-type phenotype under the conditions used [6].
• Thermoluminescence measurements indicated that high photon flux densities (>500 micromol m(-2) s(-1)) promoted oxidative stress in the chloroplasts of npq1 ML, which was associated with a loss of chlorophyll and an inhibition of the photochemical activity [7].

Anatomical context of NPQ1

• In the photoinhibition-sensitive Arabidopsis thaliana mutant NPQ1, a large but transient emission of (E)-2-hexenal was also observed a few minutes after the high-light treatment, indicating extensive damage to the membranes [8].
• De-epoxidation from the opposite, stroma side of the membrane has been investigated in the npq1 mutant from Arabidopsis thaliana (L.) Heynh. - which lacks VxDE - by adding partially purified VxDE from spinach thylakoids [9].
• In accordance with the function of two types of photoreceptors in photoinhibition, NPQ was found to offer only partial protection against photoinhibition at visible wavelengths [10].

Associations of NPQ1 with chemical compounds

• The npq1 exhibited low antheraxanthin and zeaxanthin and high violaxanthin levels and the uncoupler-sensitive amplitudes of short (< 1 ns) PS II Chl a fluorescence distribution modes were strongly inhibited compared to the WT [11].
• An npq1 lut2 double mutant was constructed, which lacks both zeaxanthin and lutein due to defects in the violaxanthin de-epoxidase and lycopene in-cyclase genes [12].
• Despite the defects in xanthophyll composition and NPQ, the npq1 lut2 mutant exhibited a remarkable ability to tolerate high light [12].
• Crosses between vtc2-2 and Arabidopsis ecotype Columbia established that the ascorbate deficiency cosegregated with the NPQ phenotype [13].
• No such effects were seen in young leaves (YL) of npq1, which were quite tolerant to strong light and eosin-induced singlet oxygen [7].

Other interactions of NPQ1

• We isolated an Arabidopsis mutant, pgr1 (proton gradient regulation), entirely lacking thermal dissipation, which was observed as little non-photochemical quenching of chlorophyll fluorescence [14].
• Plants with reduced amounts of PSI-D became light-stressed even in low light although they exhibited high non-photochemical quenching (NPQ) [15].

Analytical, diagnostic and therapeutic context of NPQ1

• Blue light-specific opening, probed by adding blue light (10 micromol m-2 s-1) to a 100 micromol m-2 s-1 red background, was found in WT, but not in npq1 or phot1 phot2 double mutant stomata [16].

References