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S-nitrosylation of protein cysteine thiol groups has recently emerged as a widespread and important reversible post-translational protein modification, involved in redox signalling pathways of nitric oxide and reactive nitrogen species. S-nitrosoglutathione reductase (GSNOR), member of class III alcohol dehydrogenase family (EC 1.1.1.1), is considered the key enzyme in the catabolism of major low molecular S-nitrosothiol, S-nitrosoglutathione, and hence to control the level of protein S-nitrosylation. Changes of GSNOR activity after exposure to different abiotic stress conditions, including low and high temperature, continuous dark and de-etiolation, and mechanical injury, were investigated in important agricultural plants. Significantly higher GSNOR activity was found under normal conditions in leaves of Cucumis spp. genotype sensitive to biotrophic pathogen Golovinomyces cichoracearum. GSNOR activity was generally increased in all studied plants by all types of stress conditions. Strong down-regulation of GSNOR was observed in hypocotyls of etiolated pea plants, which did not recover to values of green plants even 168 h after the transfer of etiolated plants to normal light regime. These results point to important role of GSNOR during normal plant development and in plant responses to several types of abiotic stress conditions.

Kubienová L., Sedlářová M., Wünschová A., Piterková J., Luhová L., Mieslerová B., Lebeda A., Navrátil M., Petřivalský M. Changes in Hsp70 gene expression and protein level were studied in three Solanum spp. genotypes in response to short-term high and low temperatures and to infection by powdery mildew. Development of Oidium neolycopersici was compared on plant leaves and leaf discs with regard to the influence of temperature. Heat and especially cold pretreatment of host tissues inhibited pathogenesis and decreased chlorophyll concentration. Exposure to heat increased Hsp70 (70 kDa heat shock proteins) content in all three genotypes of Solanum spp., whereas the infection induced the accumulation of Hsp70 only in susceptible S. lycopersicum. These results are in accordance with the suggested role of Hsp70 chaperons in plant responses to metabolic pathway disturbances triggered by pathogen challenge.

S-nitrosoglutathione reductase (GSNOR) is considered a key enzyme in the regulation of intracellular levels of S-nitrosoglutathione and protein S-nitrosylation. As a part of nitric oxide catabolism, GSNOR catalyzes the irreversible decomposition of GSNO to oxidized glutathione. GSNOR is involved in the regulation of plant growth and development, mediated by NO-dependent signaling mechanisms, and is known to play important roles in plant responses to various abiotic and biotic stress conditions. Here we present optimized protocols to determine GSNOR enzyme activities in plant samples by spectrophotometric measurements and by activity staining after the native polyacrylamide gel electrophoresis.

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