Introduction
Plants are immobile organisms that have to adapt to the ever-changing environmental conditions in their surroundings. They have a phototrophic lifestyle and need light for energy production and in the regulation of cellular processes. Fluctuations in the quantity and quality of light are likely to cause polarity in the PSII and PSI activity and the photosynthetic reaction and the carbon-fixation reactions of the Calvin cycle. The variations lower the efficiency of photosynthesis. Tobacco ( Nicotiana tabacum ) adjusts its photosynthetic response when the light intensity increases. This research has used ribosome profiling to examine the mechanisms underlying both the long-term and short-term photosynthetic responses to high light in tobacco seedlings. The results revealed the minimal contribution of chloroplast translational regulation during different light acclimations. The data also indicates that psbA translation is induced at moderate light intensities.
Results
The data revealed that changes from average light to high light caused insignificant changes in photosynthesis variables in tobacco Seedlings. An analysis of chloroplast translational regulation indicated that tobacco translation is altered very slightly after a transfer of light intensities. Ribosomes for seedlings grown at different light intensities were observed to have been recruited clearly to the psba RNA following a change from low light to high light.
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Discussion
The results indicate that ribosome occupancy, transcript accumulation, and ribosome distribution remain mostly unchanged for the predominant part of chloroplast genes. The data derived from this experiment suggests that the acclimation in different translation rates among chloroplast genes play a slight role in the familiarization to high light. The data analysis in this research indicates rapid posttranslational processes and differentiated chloroplasts dominate light acclimation but play an insignificant role in regulating gene dissemination.
Materials and Methods
The plant used was Wild-type Tobacco grown under fully controlled conditions for eight days and the seedlings later transplanted. The control conditions were 16 hours of light and 8 hours of darkness at 50,350 and 1000 umolm-2s-1; 24/20 degrees Celsius and 60% /55% humidity.
Summary
Light intensity is one of the factors that highly affect plant metabolism. However, molecular mechanisms occur at different times to ensure that complex photosynthetic stoichiometry is adjusted depending on the available light and the metabolic requirements. This research focuses on the profiling of ribosomes to examine the effects of change in light intensities on tobacco. The study on the acclimation to high light of the tobacco plant was done by growing it at 350umol m -2 s -1 for 11 days and then transferred it to 1000umol m -2 s -1 . The high light intensity only caused a minimal increase in the soil surface temperature and no consequence on the leaf’s temperature and its visual appearance. In this experiment, the physiology of the photosynthetic high light responses, chlorophyll content, a/b ratio, and fluorescence derived variables were assessed at specified time points. There were minor differences in chlorophyll content of the control plants and plants exposed to high light intensity. The a/b ratio was higher in plants with a high light intensity suggesting high light acclimation. Transcriptome-wide analysis of chloroplast translational regulation during high light acclimation was conducted by harvesting real leaves from control and treated plants at seven different time points. The results indicated translation efficiencies for all the chloroplast genes. Only minor changes were observed in translational output at a high light intensity. The differences at the RNA level at high light exposure were mild compared to those of ribosome footprints. Seedlings were grown at light intensities of 50umolm -2 s -1 and 1000umolm -2 s -1 to determine photosynthetic parameters. The increase in light intensity by 20 fold culminated to strong responses of most synthetic parameters. There was a decrease in the maximum quantum efficiency of ps11 after being exposed to high light. The translational output increased by 5-fold while all other RFs exhibited minor changes. However, the general observation is that there was minimal chance of the tobacco chloroplast gene. It can be concluded that other control mechanisms are dominant during light acclimation in the examined time frame and conditions.
References
Schuster, M., Gao, Y., Schöttler, M. A., Bock, R., & Zoschke, R. (2020). Limited responsiveness of chloroplast gene expression during acclimation to high light in tobacco. Plant Physiology , 182 (1), 424-435.
