In Silico Study of Superoxide Dismutase Gene Family in Potato and Effects of Elevated Temperature and Salicylic Acid on Gene Expression.

Potato (Solanum tuberosum L.) is the most important vegetable crop globally and is very susceptible to high ambient temperatures. Since heat stress causes the accumulation of reactive oxygen species (ROS), investigations regarding major enzymatic components of the antioxidative system are of the essence. Superoxide dismutases (SODs) represent the first line of defense against ROS but detailed in silico analysis and characterization of the potato SOD gene family have not been performed thus far. We have analyzed eight functional SOD genes, three StCuZnSODs, one StMnSOD, and four StFeSODs, annotated in the updated version of potato genome (Spud DB DM v6.1). The StSOD genes and their respective proteins were analyzed in silico to determine the exon-intron organization, splice variants, cis-regulatory promoter elements, conserved domains, signals for subcellular targeting, 3D-structures, and phylogenetic relations. Quantitative PCR analysis revealed higher induction of StCuZnSODs (the major potato SODs) and StFeSOD3 in thermotolerant cultivar Désirée than in thermosensitive Agria and Kennebec during long-term exposure to elevated temperature. StMnSOD was constitutively expressed, while expression of StFeSODs was cultivar-dependent. The effects of salicylic acid (10-5 M) on StSODs expression were minor. Our results provide the basis for further research on StSODs and their regulation in potato, particularly in response to elevated temperatures.

Effects of Exogenous Salicylic Acid on Drought Response and Characterization of Dehydrins in Impatiens walleriana.

Impatiens walleriana is a valued ornamental plant sensitive to drought stress. We investigated whether the foliar application of 2mM salicylic acid (SA) can protect potted I. walleriana plants from drought stress. The plants were divided into: watered plants, drought-stressed plants, watered plants treated with SA and drought-stressed plants treated with SA. The number of flowers and flower buds, relative water content (RWC), contents of malondialdehyde (MDA) and proline (Pro) and the activities of superoxide dismutases, catalases and peroxidases were recorded at different time points. Three dehydrin sequences were identified in de novo assembled leaf transcriptome: IwDhn1, IwDhn2.1 and IwDhn2.2. Drought stress caused wilting, floral abortion, reduction of RWC and increased MDA-an indicator of lipid peroxidation. In response to drought, Impatiens accumulated Pro and induced chloroplastic Cu/ZnSOD and two peroxidase isoforms. The most remarkable drought response was strong induction of IwDhn2.1 and IwDhn2.2. Rehydration restored RWC, Pro level, Cu/ZnSOD activity and dehydrins expression in drought-stressed plants approximately to the values of watered plants.SA had ameliorating effects on plants exposed to drought, including prevention of wilting, preservation of RWC, increased Pro accumulation, modulation of antioxidative activities and remarkable decrease of lipid peroxidation, but without effects on flowers' preservation.

Expression of protein synthesis elongation factors in winter wheat and oat in response to heat stress.

The aim of our work was to examine the expression and accumulation of EF-Tu and eEF1A in grain filing stage of five genotypes of winter wheat and one oat genotype in conditions of heat stress. In addition, the correlation between accumulation of elongation factors eEF1A and EF-Tu, and yield components of cereals in the field was investigated. Flag leaf protein samples were analyzed by immunoblotting. Flag leaves were collected under conditions of moderate (23 °C; MT) and high air temperature (38 °C; HT) in a field experiment. After the harvest, grain yield was determined. The yield components, the weight of dry seed and grains number per spike, were assessed in the stage of full physiological maturity of investigated cultivars. Obtained results revealed a difference in the level of EF-Tu accumulation both under conditions of moderate air temperatures and conditions of heat stress among investigated cultivars. Cultivar Zvezdana was the only one that showed increase in EF-Tu accumulation under HT (25%) compared to MT. Immunoblot analysis indicated that the highest increase of eEF1A accumulation (43%) in relation to moderate temperature was detected in cultivar Talas. A significant, positive, linear correlation was found between the expression of eEF1A and small grains productivity under heat-stress conditions.

Heat-induced accumulation of protein synthesis elongation factor 1A implies an important role in heat tolerance in potato.

MAIN CONCLUSION: Potato eukaryotic elongation factor 1A comprises multiple isoforms, some of which are heat-inducible or heat-upregulated and might be important in alleviating adverse effects of heat stress on plant productivity. Heat stress substantially reduces crop productivity worldwide, and will become more severe due to global warming. Identification of proteins involved in heat stress response may help develop varieties for heat tolerance. Eukaryotic elongation factor 1A (eEF1A) is a cytosolic, multifunctional protein that plays a central role in the elongation phase of translation. Some of the non-canonical eEF1A activities might be important in developing plant heat-stress tolerance. In this study, we investigated effects of heat stress (HS) on eEF1A expression at the protein level in potato, a highly heat vulnerable crop. Our results from both the controlled environment and the field have shown that potato eEF1A is a heat-inducible protein of 49.2-kDa with multiple isoforms (5-8). Increase in eEF1A abundance under HS can be mainly attributed to 2-3 basic polypeptides/isoforms. A significant correlation between eEF1A abundance and the potato productivity in the field was observed in two extremely hot years 2011 and 2012. Genomic Southern blot analysis indicated the existence of multiple genes encoding eEF1A in potato. Identification, isolation and utilization of heat-inducible eEF1A genes might be helpful for the development of the heat-tolerant varieties.