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Three varieties (cv. Pobeda, Katya and Sadovo) of winter wheat (Triticum aestivum), differing in their agronomic characteristics, were analysed during progressive soil water stress and recovery at early vegetation stages. Changes in abscisic acid content, SDS-PAGE and immunoblot profiles of proteins that remained soluble upon heating were monitored. Initially higher ABA content in control Pobeda and Katya corresponded to earlier expression of the studied late embryogenesis abundant (LEA) proteins. A combination of higher ABA content, early immunodetection of dehydrins, and a significant increase of WZY2 transcript levels were observed in drought-stressed leaves of the tolerant variety Katya. One-step RT-PCR analyses of some acidic dehydrin genes (WCOR410b, TADHN) documented their relatively constant high expression levels in leaves under drought stress during early vegetative development. Neutral WZY2 dehydrin, TaLEA2 and TaLEA3 transcripts accumulated gradually with increasing water deficit. Delayed expression of TaLEA2 and TaLEA3 genes was found in the least drought-tolerant wheat, Sadovo. The expression profile of WZY2 revealed two distinct and separate bands, suggesting alternative splicing, which altered as water stress increased.

The involvement of acidic proteases in soil drought response of winter wheat (Triticum aestivum L.) at seedling stage in three cultivars differing in water stress tolerance was studied. Withholding irrigation for seven days resulted in severe drought stress corresponding to 60% leaf water deficit. Stressed plants were recovered by providing optimal water supply for 3 days. Reversible changes in leaf pigment and protein content were registered, being least expressed in the drought-resistant cultivar Katya. Protein loss was inversely related to the increase in total proteolytic activity at pH 5 and in aminopeptidase activity at pH 7. Quantitative differences among the cultivars were established only for azocaseinolytic activity (pH 5). The drought-resistant cultivar (Katya) showed relatively little increase in acid protease activity whereas the highest values of this activity were detected in cultivar Pobeda. In-gel staining for cysteine-activated proteases revealed four to five separate activity bands. The upper band, specifically inhibited by E-64, was raised at severe drought. Transcript abundance of two wheat cysteine proteases -Ta.61026 putative thiol protease, and WCP2 peptidase of papain type was analyzed by RT-PCR. Gene expression of the cysteine proteases under study was suppressed in the drought-tolerant cultivar, while in the less resistant ones it remained unchanged or augmented. The results suggest that lower proteolytic activity and decreased expression of certain cysteine protease genes under water deficit during early developmental stage could be regarded as an indicator for drought resistance of winter wheat cultivars., (Copyright 2009 Elsevier Masson SAS. All rights reserved.)

The main objective of the present work was to examine leaf respiratory responses to dehydration and subsequent recovery in three varieties of winter wheat (Triticum aestivum L.) known to differ in their level of drought tolerance. Under dehydration, both total respiration and salicylhydroxamic acid (SHAM)-resistant cytochrome (Cyt) pathway respiration by leaf segments decreased significantly compared with well-watered plants. This decrease was more pronounced in the drought-sensitive Sadovo and Prelom genotypes. In contrast, the KCN-resistant SHAM-sensitive alternative (Alt) pathway became increasingly engaged, and accounted for about 80% of the total respiration. In the drought-tolerant Katya variety, increased contribution of the Alt pathway was accompanied by a slight decrease in Cyt pathway activity. Respiration of isolated leaf mitochondria also showed a variety-specific drought response. Mitochondria from drought-sensitive genotypes had low oxidative phosphorylation efficiency after dehydration and rewatering, whereas the drought-tolerant Katya mitochondria showed higher phosphorylation rates. Morphometric analysis of leaf ultrastructure revealed that mitochondria occupied approximately 7% of the cell area in control plants. Under dehydration, in the drought-sensitive varieties this area was reduced to about 2.0%, whereas in Katya it was around 6.0%. The results are discussed in terms of possible mechanisms underlying variety-specific mitochondrial responses to dehydration.

Proteases and their specific inhibitors are ubiquitously distributed and play a key regulatory role in many biological processes. Gene expression and activity of certain proteases has been shown to increase in Triticum aestivum L. leaves under drought, with a major contribution of cysteine proteases, especially in sensitive wheat varieties. However, little is known about the stress response of protease inhibitors (PIs) and their role in the regulation of intracellular proteolysis. In this study the changes in transcript abundance of some protease inhibitors (belonging to cystatin and serpin classes) were evaluated by semi-quantitative RT-PCR in leaves and roots of winter wheat seedlings from two varieties with differing tolerance. The expression of two cysteine proteases in the same samples was also assessed. The expression of the studied genes was compared in the tolerant variety "Katya" and the more susceptible to water deprivation variety "Sadovo", applying severe but recoverable soil drought. Growth inhibition and stress related parameters confirmed the relatively higher drought sensitivity of variety "Sadovo". Serpin transcript abundance in control roots was higher than in the leaves. An opposite trend was documented for cystatins – the level of their expression was stronger in the non-treated leaves compared to roots. Drought stress inhibited PI expression in roots, while varying effects on the transcript levels were detected in the leaves of water deprived plants. The levels of the two cysteine protease transcripts under drought exhibited organ-specific response – they declined in roots, and increased in leaves. Further detailed studies using more sensitive methods are necessary to evaluate the potential of protease inhibitors as biochemical markers for drought tolerance. [ABSTRACT FROM AUTHOR]

Transformed tobacco plants expressing a rice cysteine proteinase inhibitor (OC-I) and non-transformed plants were grown in a controlled environment and subjected to various stresses. Two-month-old transformed and non-transformed plants were exposed for 5 days to drought conditions by withholding watering. High temperature (40 °C) was applied additionally at day 6th for 5 h either individually or in combination with drought. All stress treatments were applied under low (150 μmol m−2 s−1 PPFD) and high light intensity (HL) of 1000 μmol m−2 s−1 PPFD to determine if OC-I expression might provide protection under combination of stresses usually existing in nature. Drought stress led to diminution in leaf relative water content, photosynthesis inhibition, decrease in chlorophyll content and accumulation of malondialdehyde and proline. Heat stress alone did not affect the plants significantly, but intensified the effect of drought stress. HL intensity further increased the proline content. OC-I transformed plants grown under low light intensity had significantly higher total superoxide dismutase and guaiacol peroxidase activities as well as their isoforms than non-transformed control plants under non-stress and stress conditions. Catalase activity was not highly affected by OC-I expression. Results indicate that OC-I expression in tobacco plants provides protection of the antioxidative enzymes superoxide dismutase and guaiacol peroxidise under both non-stress and stress conditions. [ABSTRACT FROM AUTHOR]