Abstract
Acclimation to changing light intensities poses major challenges to plant metabolism and has been shown to involve regulatory adjustments in chloroplast gene expression. However, this regulation has not been examined at a plastid genome-wide level and for many genes, it is unknown whether their expression responds to altered light intensities. Here, we applied comparative ribosome profiling and transcriptomic experiments to analyze changes in chloroplast transcript accumulation and translation in leaves of tobacco (Nicotiana tabacum) seedlings after transfer from moderate light to physiological high light. Our time-course data revealed almost unaltered chloroplast transcript levels and only mild changes in ribosome occupancy during 2 d of high light exposure. Ribosome occupancy on the psbA mRNA (encoding the D1 reaction center protein of PSII) increased and that on the petG transcript decreased slightly after high light treatment. Transfer from moderate light to high light did not induce substantial alterations in ribosome pausing. Transfer experiments from low light to high light conditions resulted in strong PSII photoinhibition and revealed the distinct light-induced activation of psbA translation, which was further confirmed by reciprocal shift experiments. In low-light-to-high-light shift experiments, as well as reciprocal treatments, the expression of all other chloroplast genes remained virtually unaltered. Altogether, our data suggest that low light-acclimated plants upregulate the translation of a single chloroplast gene, psbA, during acclimation to high light. Our results indicate that psbA translation activation occurs already at moderate light intensities. Possible reasons for the otherwise mild effects of light intensity changes on gene expression in differentiated chloroplasts are discussed.
Highlights
Plants are sessile organisms that must cope in situ with ever-changing environmental conditions
Our results revealed only small contributions of translational regulation during short, medium, and long-term high-light acclimation
To study acclimation to high light in the model dicotyledonous C3 plant tobacco, plants were grown at 350 μmol m-2 s-1 for 11 days before they were shifted to 1000 μmol m-2 s-1 (Fig. 1)
Summary
Plants are sessile organisms that must cope in situ with ever-changing environmental conditions. Due to the phototrophic lifestyle of plants, light dramatically influences plant metabolism. Light serves as both an energy source and a signal that controls diverse cellular processes. Plants perceive light through different photoreceptors which regulate nuclear gene expression (e.g., Gyula et al 2003, Kami et al 2010, Jenkins 2014). The photosynthetic reactions within chloroplasts are directly affected by alterations in light conditions and serve as a “metabolic light sensor”. Changes in light quantity and quality cause imbalances in the activities of photosystems I and II (PSI and PSII), and between the light reactions of photosynthesis and the carbon fixation reactions of the Calvin-Benson-Bassham cycle (CBC)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
