Light spectrum modifies the drought-induced changes of glutathione and free amino acid levels in wheat

Abstract

The proposed spectral control of the adaptive metabolic responses to drought was tested by the comparison of two wheat genotypes with different stress tolerance. White light was used as the reference to see the effects of the three altered ratios of blue, red, and far-red spectral components, which conditions are referred to as blue, pink, and far-red lights. Under all spectral conditions, drought greatly reduced the growth of both genotypes. However, the glutathione content decreased and the proline level increased, independently of the spectrum, only in the sensitive genotype. Far-red light greatly decreased the amount of cystine and glutathione disulphide during the stress which resulted in their lower ratios compared to the reduced forms only in the tolerant genotype. The maintained more reducing redox environment contributes to its better stress tolerance. In far-red light, drought induced a greater accumulation of several free amino acids (mHis, Val, Ile, Leu, Asn, His, Tyr, Lys, Arg) in the tolerant genotype, while a smaller one in the sensitive genotype compared to the other spectral conditions. The transcript level of the genes related to amino acid and glutathione metabolism was also different between the two genotypes under this condition. The present results indicate the adaptive adjustment of glutathione and amino acid levels by far-red light during drought which observation can serve as a basis for the spectrum-dependent modification of the protective metabolites (glutathione, proline) of crops to reduce the stress-induced damages.