We have examined the correlation between heat tolerance and small heat shock protein (sHSP) expression under heat stress conditions in potato (Solanum tuberosum L.). The relative heat tolerance of nine potato cultivars grown under greenhouse conditions was determined using the electrolyte leakage assay (ELA), a standard quantitative assay for heat tolerance. Three cultivars differing in heat tolerance were selected and designated as heat-tolerant (‘Laura’), moderately sensitive (‘Liseta’) and heat-sensitive (‘Agria’) genotypes. The expression of cytosolic HSP18 and chloroplast HSP21 was analyzed at the protein level in the leaves of selected cultivars, both ex vitro- and in vitro-grown, after heat stress or control treatment. Immunoblot analysis revealed heat-induced HSP18 and HSP21 expression in all examined genotypes. A similar pattern of examined sHSP expression was observed ex vitro and in vitro: heat-tolerant ‘Laura’ accumulated higher levels of both HSP18 and HSP21 compared to heat-sensitive ‘Liseta’ and ‘Agria’. Our results indicate that ELA combined with immunoblot analysis of sHSP accumulation under HS conditions, might be considered as a reliable procedure in screening potato genotypes for heat tolerance. To our knowledge, this is the first study where sHSP expression between ex vitro- and in vitro-grown potato plants was compared

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.

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.

Potato (Solanum tuberosum L.) plants are highly vulnerable to heat stress. Even moderately elevated temperatures can disturb the process of tuberization in this important crop, causing a decline in tuber initiation, a reduction in tuber bulking, and tuber disorders. In the present study, we investigated the effects of heat stress on tuberization in two potato cultivars, the heat-sensitive cultivar Désirée and the heat-tolerant cultivar Festival, using an in vitro system. A temperature of 29 °C reduced tuber initiation and tuber bulking, and stimulated shoot elongation in cv. Désirée, while this temperature treatment did not significantly alter tuberization or shoot elongation in cv. Festival. In addition, high temperature interfered with the onset of microtuber dormancy and promoted growth of tuber apical buds during the tuber bulking stage in both cultivars. Stress-responsive proteins HSP17.6-CI, HSP101, and eEF1A showed heat-induced accumulation patterns in shoots and microtubers of these two cultivars, with the exception of a decline in the abundance of eEF1A in cv. Désirée microtubers under heat stress. High levels of HSP17.6-CI in microtubers of cv. Désirée did not ameliorate the effects of heat stress on tuberization of this relatively heat-sensitive cultivar. Conversely, a higher level of eEF1A under heat stress in microtubers of the heat-tolerant cv. Festival indicated a possible function of this protein in alleviating the negative effects of high temperature on potato tuberization. This study suggested that analysis of stress-responsive proteins in potato microtubers combined with assessment of tuberization parameters in vitro may represent a useful screening procedure for selection of heat-tolerant potato genotypes.

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