Reactive oxygen species and transcript analysis upon excess light treatment in wild-type <it>Arabidopsis thaliana </it>vs a photosensitive mutant lacking zeaxanthin and lutein

• Main Authors: Roncaglia Enrica, Carillo Petronia, Aprile Alessio, Dall'Osto Luca, Alboresi Alessandro, Cattivelli Luigi, Bassi Roberto
• Format: Article
• Language: English
• Published: BMC 2011-04-01
• Series: BMC Plant Biology
• Online Access: http://www.biomedcentral.com/1471-2229/11/62

<p>Abstract</p> <p>Background</p> <p>Reactive oxygen species (ROS) are unavoidable by-products of oxygenic photosynthesis, causing progressive oxidative damage and ultimately cell death. Despite their destructive activity they are also signalling molecules, priming the acclimatory response to stress stimuli.</p> <p>Results</p> <p>To investigate this role further, we exposed wild type <it>Arabidopsis thaliana </it>plants and the double mutant <it>npq1lut2 </it>to excess light. The mutant does not produce the xanthophylls lutein and zeaxanthin, whose key roles include ROS scavenging and prevention of ROS synthesis. Biochemical analysis revealed that singlet oxygen (¹O₂) accumulated to higher levels in the mutant while other ROS were unaffected, allowing to define the transcriptomic signature of the acclimatory response mediated by ¹O₂which is enhanced by the lack of these xanthophylls species. The group of genes differentially regulated in <it>npq1lut2 </it>is enriched in sequences encoding chloroplast proteins involved in cell protection against the damaging effect of ROS. Among the early fine-tuned components, are proteins involved in tetrapyrrole biosynthesis, chlorophyll catabolism, protein import, folding and turnover, synthesis and membrane insertion of photosynthetic subunits. Up to now, the <it>flu </it>mutant was the only biological system adopted to define the regulation of gene expression by ¹O₂. In this work, we propose the use of mutants accumulating ¹O₂by mechanisms different from those activated in <it>flu </it>to better identify ROS signalling.</p> <p>Conclusions</p> <p>We propose that the lack of zeaxanthin and lutein leads to ¹O₂accumulation and this represents a signalling pathway in the early stages of stress acclimation, beside the response to ADP/ATP ratio and to the redox state of both plastoquinone pool. Chloroplasts respond to ¹O₂accumulation by undergoing a significant change in composition and function towards a fast acclimatory response. The physiological implications of this signalling specificity are discussed.</p>