Cysteine proteinases also referred to as thiol proteases play an essential role in plant growth and development but also in senescence and programmed cell death, in accumulation of storage proteins such as in seeds, but also in storage protein mobilization. Thus, they participate in both anabolic and catabolic processes. In addition, they are involved in signalling pathways and in the response to biotic and abiotic stresses. In this review an attempt was undertaken to illustrate these multiple roles of cysteine proteinases and the mechanisms underlying their action.

The physiological responses of potato (Solanum tuberosum L) cultivars to soil drought at the tuberization phase and their impact on agronomically important traits were investigated in potted plants under semi-controlled conditions. Genotypedependent responses of potato to water deficiency were evaluated on two pairs (tolerant/sensitive) of Polish cultivars. Each pair of cultivars had a similar genetic background but was extremely different in terms of drought tolerance evaluated on

SummaryPotato is one of the four most important food crop plants worldwide and is strongly affected by drought. The following two pairs of potato cultivars, which are related in ancestry but show different drought tolerances, were chosen for comparative gene expression studies: Gwiazda/Oberon and Tajfun/Owacja. Comparative RNA‐seq analyses of gene expression differences in the transcriptomes obtained from drought‐tolerant versus drought‐sensitive plants during water shortage conditions were performed. The 23 top‐ranking genes were selected, 22 of which are described here as novel potato drought‐responsive genes. Moreover, all but one of the potato genes selected have homologues in the Arabidopsis genome. Of the seven tested A. thaliana mutants with altered expression of the selected homologous genes, compared to the wild‐type Arabidopsis plants, six showed an improved tolerance to drought. These genes encode carbohydrate transporter, mitogen‐activated protein kinase kinase kinase 15 (MAPKKK15), serine carboxypeptidase‐like 19 protein (SCPL19), armadillo/beta‐catenin‐like repeat‐containing protein, high‐affinity nitrate transporter 2.7 and nonspecific lipid transfer protein type 2 (nsLPT). The evolutionary conservation of the functions of the selected genes in the plant response to drought confirms the importance of these identified potato genes in the ability of plants to cope with water shortage conditions. Knowledge regarding these gene functions can be used to generate potato cultivars that are resistant to unfavourable conditions. The approach used in this work and the obtained results allowed for the identification of new players in the plant response to drought.

Potato (Solanum tuberosum L.) is highly sensitive to soil drought and extracts less of the available water from the soil than other crops. Even a very short period of water shortage has a negative effect on consumptive and technological properties of potato tubers. The cause of the poorer properties of potato tubers might not only be water shortage itself but could also be the enhanced production of reactive oxygen species (ROS) accompanying practically every kind of stress, both biotic and abiotic. However, antioxidative enzymes seem to counteract the ROS accumulation and, thus, might protect plants against the deleterious effects of environmental stresses. Our research shows that increased activity of peroxidase, superoxide dismutase and catalase protects plants from oxidative stress, and, consequently, against yield losses.

Changes in proteolytic activities in response to water deficiency have been investigated in ten genotypes of spring wheat (Triticum aestivum L.) differing in response to water deficit stress and ability to acclimate. To determine subcellular localization and the type of proteases, mesophyll protoplasts isolated from wheat leaves were purified. Proteolytic activities were assayed using azocasein in the case of vacuolar proteinases at pH 5.0 and 125I-lysozyme in the case of extravacuolar ATP-dependent proteinases at pH 8.2. ATP-dependent proteolytic activity was found to be confined to the extravacuolar fraction while the azocaseinolytic activity to vacuoles. Dehydration increased vacuolar azocaseinolytic activity at both stages of plant development (shooting and heading), but the increase was significantly lower in more tolerant genotypes. The extravacuolar energy-dependent 125I-lysozyme degradation was low at the shooting stage but it was higher in the genotypes with a greater critical water saturation deficit. At the heading phase in the non-acclimated flag leaves ATP-dependent 125I-lysozyme degradation decreased in a genotype-dependent manner, but was enhanced upon acclimation to the same extent irrespective to the genotype ability to acquire dehydration tolerance during acclimation. The results presented indicate that both pathways of protein degradation are interlinked upon dehydration and are genotype dependent.