Abscisic acid (ABA) is well-known phytohormone involved in the control of plant natural developmental processes, as well as the stress response. Although in wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) its role in mechanism of the tolerance to most common abiotic stresses, such as drought, salinity, or extreme temperatures seems to be fairly well recognized, not many authors considered that changes in ABA content may also influence the sensitivity of cereals to adverse environmental factors, e.g., by accelerating senescence, lowering pollen fertility, and inducing seed dormancy. Moreover, recently, ABA has also been regarded as an element of the biotic stress response; however, its role is still highly unclear. Many studies connect the susceptibility to various diseases with increased concentration of this phytohormone. Therefore, in contrast to the original assumptions, the role of ABA in response to biotic and abiotic stress does not always have to be associated with survival mechanisms; on the contrary, in some cases, abscisic acid can be one of the factors that increases the susceptibility of plants to adverse biotic and abiotic environmental factors.

Abscisic acid (ABA) is a phytohormone that plays a key role in regulating several developmental processes as well as in response to stressful conditions such as drought. Activation of the ABA signaling cascade allows the induction of an appropriate physiological response. The basic components of the ABA signaling pathway have been recognized and characterized in recent years. Pyrabactin resistance, pyrabactin resistance-like, and the regulatory component of ABA receptors (PYR/PYL/RCAR) are the major components responsible for the regulation of the ABA signaling pathway. Here, we review recent findings concerning the PYR/PYL/RCAR receptor structure, function, and interaction with other components of the ABA signaling pathway as well as the termination mechanism of ABA signals in plant cells. Since ABA is one of the basic elements related to abiotic stress, which is increasingly common in the era of climate changes, understanding the perception and transduction of the signal related to this phytohormone is of paramount importance in further increasing crop tolerance to various stress factors.

The present work demonstrates that the transition of wheat (Triticum aestivum L.) seedlings from dehydration tolerance to intolerance on the fifth day following imbibition is associated with a disturbance in cellular redox homeostasis. During germination the ratio of reduced (AsA) to oxidized ascorbate (DHA) was lower in the tolerant 4-day-old seedlings compared to the sensitive 6-day-old seedlings because of the lower ascorbate content in the former. The reduced glutathione (GSH) and total glutathione (GSH ? GSSG) pools were higher in tolerant seedlings and remained higher upon dehydration. The development of dehydration intolerance with a seedling age coincided with a 50 % loss of the total glutathione pool and a shift of GSH/GSSG to a more oxidized state. Activities of ascorbate peroxidase and glutathione reductase increased with water deficiency in both tolerant and sensitive seedlings but the three new activity bands appeared only in sensitive seedlings. The stable ratio of GSH/GSSG and a higher AsA/DHA ratio in sensitive seedlings did not prevent the enhanced production of H2O2 and the peroxidation of lipids with dehydration. As a result, an increase in the protein carbonyl group and a significant decrease in the thiol groups were observed in dehydrated sensitive seedlings. Water deficiency enhanced the total azocaseinolytic activity, mainly in sensitive seedlings. The highest increase in protein carbonylation and lowest azocaseinolytic activity was observed at the beginning of seedling dehydration (15-25 % WSD) being in a sensitive phase of growth. The presented results indicate that the development of dehydration intolerance during the transition of wheat seedlings from heterotrophic to autotrophic growth is associated with an alterations in protein oxidation.

Main conclusionIn maize, leaf proteome responses evoked by soil drought applied separately differ from those evoked by mite feeding or both types of stresses occurring simultaneously.This study focuses on the involvement of proteomic changes in defence responses of a conventional maize cultivar (Bosman) to the two-spotted spider mite infestation, soil drought and both stresses coexisting for 6 days. Under watering cessation or mite feeding applied separately, the protein carbonylation was not directly linked to the antioxidant enzymes’ activities. Protein carbonylation increased at higher and lower SOD, APX, GR, POX, PPO activities following soil drought and mite feeding, respectively. Combination of these stresses resulted in protein carbonylation decrease despite the increased activity of all antioxidant enzymes (except the CAT). However, maize protein network modification remains unknown upon biotic/abiotic stresses overlapping. Here, using multivariate chemometric methods, 94 leaf protein spots (out of 358 considered; 2-DE) were identified (LC–MS/MS) as differentiating the studied treatments. Only 43 of them had individual discrimination power. The soil drought increased abundance of leaf proteins related mainly to photosynthesis, carbohydrate metabolism, defence (molecular chaperons) and protection. On the contrary, mite feeding decreased the abundance of photosynthesis related proteins and enhanced the abundance of proteins protecting the mite-infested leaf against photoinhibition. The drought and mites occurring simultaneously increased abundance of proteins that may improve the efficiency of carbon fixation, as well as carbohydrate and amino acid metabolism. Furthermore, increased abundance of the Rubisco large subunit-binding protein (subunit β), fructose-bisphosphate aldolase and mitochondrial precursor of Mn-SOD and decreased abundance of the glycolysis-related enzymes in the mite-free leaf (in the vicinity of mite-infested leaf) illustrate the involvement of these proteins in systemic maize response to mite feeding.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-016-2559-6) contains supplementary material, which is available to authorized users.

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