Light intensity and spectrum affect metabolism of glutathione and amino acids at transcriptional level

Abstract

The effects of various light intensities and spectral compositions on glutathione and amino acid metabolism were compared in wheat. Increase of light intensity (low—normal—high) was accompanied by a simultaneous increase in the shoot fresh weight, photosynthetic activity and glutathione content. These parameters were also affected by the modification of the ratios of blue, red and far-red components (referred to as blue, pink and far-red lights) compared to normal white light. The photosynthetic activity and the glutathione content decreased to 50% and the percentage of glutathione disulfide (characterising the redox state of the tissues) in the total glutathione pool doubled in far-red light. The alterations in the level and redox state of the antioxidant glutathione resulted from the effect of light on its synthesis as it could be concluded from the changes in the transcription of the related genes. Modification of the light conditions also greatly affected both the amount and the ratio of free amino acids. The total free amino acid content was greatly induced by the increase of light intensity and was greatly reduced in pink light compared to the normal intensity white light. The concentrations of most amino acids were similarly affected by the light conditions as described for the total free amino acid content but Pro, Met, Thr, ornithine and cystathionine showed unique response to light. As observed for the amino acid levels, the expression of several genes involved in their metabolism also enhanced due to increased light intensity. Interestingly, the modification of the spectrum greatly inhibited the expression of most of these genes. Correlation analysis of the investigated parameters indicates that changes in the light conditions may affect growth through the adjustment of photosynthesis and the glutathione-dependent redox state of the tissues. This process modifies the metabolism of glutathione and amino acids at transcriptional level.

Comparison of Light Condition-Dependent Differences in the Accumulation and Subcellular Localization of Glutathione in Arabidopsis and Wheat

“…The increase was derived from the activation of its synthesis as shown by the parallel increase in the level of its precursors, Cys and Gly. The light intensity-dependent accumulation of the third GSH precursor, Glu, was observed in wheat seedlings [ 4 ]. The induction of GSH synthesis by high light was also shown in the flag leaves of wheat based on the accumulation of the intermediate product, γ-glutamylcysteine [ 19 ].…”

“…Temporal and spatial changes in light conditions occurring during the day, season and year or at various altitudes and latitudes [ 1 ] influence reactive oxygen species (ROS) production, and thus the antioxidant scavenging system, including the ascorbate-glutathione cycle [ 2 , 3 , 4 ]. Glutathione is a central component of the redox system participating in adjusting growth and development to changing environmental conditions including alterations in the intensity and spectrum of light.…”

“…Zechmann [ 18 ] confirmed a diurnal rhythm for glutathione content in cell compartments, with the lowest values at the end of the night, maximum values after 3 h of light and a strong decrease within the next 1–2 h. Besides light intensity, the proportion of blue, red and far-red spectral components also influenced the amount of glutathione in flag leaves of wheat [ 19 ]. Both blue light and low red/far-red ratio reduced the glutathione content [ 4 , 19 ]. In addition, shaded leaves of bean exposed to a low red/far-red ratio had a much lower glutathione reductase (GR) activity and reduced glutathione (GSH) level compared to those ones grown in full light with equal red/far-red ratios [ 20 , 21 ].…”

“…We hypothesize that changes in the light intensity and spectrum may affect the antioxidant system, and thus likewise the size and redox state of the glutathione pool in the plants. The aim of the present study was the comparison of the light condition-dependent (the conditions were selected on the basis of our previous results, [ 4 , 19 ]) differences in the accumulation and subcellular localization of glutathione in the leaves of the dicotyledonous Arabidopsis and monocotyledonous wheat. Furthermore, the wild type Arabidopsis plants (Col-0), ascorbate- and glutathione-deficient mutants ( vtc2-1 and pad2-1 ) were also included into the experiments in order to see the effect of altered ascorbate and glutathione levels on the response to the various light conditions.…”

Catalyzing Holistic Agriculture Innovation Through Industrial Biotechnology

“…292 With the ease of controlling the type of light emitted by LEDs, plant scientists and horticulturists are exploring lighting effects on plant growth, morphology, and metabolism. [295][296][297][298] This creates opportunities to intervene in plant production systems with specificity that has been impossible to accomplish in the past.…”