Abstract
Among the environmental alterations accompanying oncoming climate changes, drought is the most important factor influencing crop plant productivity. In plants, water deficit ultimately results in the development of oxidative stress and accumulation of osmolytes (e.g. amino acids and carbohydrates) in all tissues. Up-regulation of sugar biosynthesis in parallel to the increasing overproduction of reactive oxygen species (ROS) might enhance protein glycation, i.e. interaction of carbonyl compounds, reducing sugars and α-dicarbonyls with lysyl and arginyl side-chains yielding early (Amadori and Heyns compounds) and advanced glycation end-products (AGEs). Although the constitutive plant protein glycation patterns were characterized recently, the effects of environmental stress on AGE formation are unknown so far. To fill this gap, we present here a comprehensive in-depth study of the changes in Arabidopsis thaliana advanced glycated proteome related to osmotic stress. A 3 d application of osmotic stress revealed 31 stress-specifically and 12 differentially AGE-modified proteins, representing altogether 56 advanced glycation sites. Based on proteomic and metabolomic results, in combination with biochemical, enzymatic and gene expression analysis, we propose monosaccharide autoxidation as the main stress-related glycation mechanism, and glyoxal as the major glycation agent in plants subjected to drought.
Highlights
Environmental stress is one of the major factors reduc- Carvalho, 2008)
Clear loss of turgor was observed with the plants transferred to pots infused with polyethylene glycol (PEG) (Fig. 2A, B), the water potential did not change in comparison with the controls (Fig. 2C)
The observed plant dehydration was accompanied by a 14.3-fold increase of abscisic acid (ABA) content (t-test, P=0.001, Fig. 3A), stomata closure (Fig. 3B, t-test, P=1.1 × 10–5), and a reduction of photosystem II (PSII) efficiency (t-test, P=7.1 × 10–4, Fig. 3C), whereas the leaf relative water content (LRWC) and chlorophyll contents were unchanged (Supplementary Fig. S1A, B)
Summary
Environmental stress is one of the major factors reduc- Carvalho, 2008). The oncoming climate changes are making ing crop plant productivity all over the world, and drought drought, usually defined as a period of lower than normal represents its most important manifestation (Cruz de precipitation that limits a plant’s productivity in a natural6284 | Paudel et al.or agricultural system (Brunner et al, 2015), an important economic factor directly influencing the yield and quality of crops. Water deficiency triggers reduction of stomatal aperture, decrease of CO2 assimilation rate and growth inhibition (Chaves et al, 2009) This leads to an imbalance between the generation of reduction equivalents by the light reactions and their consumption in the Calvin cycle. This increases the rates of single electron reduction of molecular oxygen by the redox proteins of the chloroplasts and mitochondrial electron transport chains and enhances production of reactive oxygen species (ROS): first, singlet oxygen (1O2) and superoxide anion radical (O2−), and further, hydrogen peroxide (H2O2), nitric oxide (NO) and the hydroxyl radical (OH) (Kar, 2011). The generated products of lipid and sugar oxidative degradation, hydroxycarbonyls and α-oxocarbonyls, are potent protein modification agents and can trigger essential changes in the structure and function of polypeptides (Lennicke et al, 2016)
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