Wheat development depending on light induced redox changes

We want to study the light quantity- and quality-dependent metabolism and signalling pathways in wheat. For this purpose, the effect of light intensity and quality on the redox-mediated changes in photosynthesis, transcript and metabolite levels, growth and development will be investigated at both optimal and at low temperature, which influences strongly the photosynthetic electron transport, as well as the redox mediated processes. The concentration and redox state of the two major antioxidants, ascorbate and glutathione as well as the activity of antioxidant enzymes and the concentration of free amino acids and polyamines will be compared in various organs and in cell compartments. In addition, the study the redox-responsive genes will clarify whether the changes in metabolite levels derives from transcriptional regulation. Based on the proposed relationships between the studied parameters the project will enable the creation of models with light quantity and quality-dependent metabolic and signalling pathways. The Hungarian partner has possibility for the modification light quality and quantity using led illumination which allows the study the effect of light on the redox environment and the various molecular, biochemical and physiological parameters. The Austrian partner has great experience in the subcellular investigation of ascorbate, glutathione and glutathione precursors. The combination of knowledge and infrastructure in the two laboratories enables a more complex approach of the scientific problems to be studied and will reveal deeper relationships.

The aim of this joint project was to monitor the effects of light intensity and spectrum composition of the metabolism and its regulation for growth and development in wheat and to address some of these parameters likewise in the model plant Arabidopsis thaliana. We examined effects of light intensity and spectrum composition on redox-mediated changes in photosynthesis, expression of glutathione associated genes and metabolite levels under optimal and in wheat additionally under low temperature conditions, because low temperature is known to strongly affect photosynthesis related electron transport and redox-mediated processes. Increased light intensity enhanced the positive correlation of cold mediated changes in the redox state of the glutathione pool and freezing tolerance. The concentration and redox-state of one of the major antioxidants, glutathione and concentration of aminoacids and polyamines was monitored in different plant organs and cell compartments. We found for instance, that increased light intensity and low red/far-red light induced subcellular glutathione concentration in a glutathione deficient Arabidopsis mutant (pad2-1) and in wheat similarly, but not in the Arabidopsis wildtype (Col-0). Our findings confirm that monitoring glutathione content at the cell compartment level is of great importance in understanding the regulatory fine-tuning of redox processes. Expression analysis of redox-associated genes (mRNAs and miRNAs) has shown that the light mediated changes of metabolite levels in wheat were regulated at the transcriptional level, whereas other regulatory mechanisms are at work in Arabidopsis. Our results have given valuable insights into the interaction of the parameters examined in this joint project and thus contribute to the development of a model which may explain light dependent metabolite and signal transduction pathways of antioxidants in plants. The Hungarian partners conducted the manipulation of light intensity and spectrum composition experiments using LEDs, which allowed for monitoring effects of light on the redox environment as well as on the molecular, biochemical and physiological parameters. The Austrian partners have a long-standing expertise in the localization of ascorbate, glutathione and glutathione precursors within plant cell organelles. The combination of know-how and facilities of the two labs allowed for complex experimental set-ups and in that way contributes to a better understanding of certain aspects of open research questions.