Abstract
Main conclusion The interaction between enzymatic and non-enzymatic antioxidants, endogenous levels of ABA and ABA-GE, the rapid recuperation of photosynthetic proteins under re-watering as well the high level of antioxidant proteins in previously drought-stressed plants under re-watering conditions, will contribute to drought resistance in plants subjected to a long-term drought stress under Mediterranean field conditions. This work provides an overview of the mechanisms of Cistus albidus acclimation to long-term summer drought followed by re-watering in Mediterranean field conditions. To better understand the molecular mechanisms of drought resistance in these plants, a proteomic study using 2-DE and MALDI-TOF/TOF MS/MS was performed on leaves from these shrubs. The analysis identified 57 differentially expressed proteins in water-stressed plants when contrasted to well watered. Water-stressed plants showed an increase, both qualitatively and quantitatively, in HSPs, and downregulation of photosynthesis and carbon metabolism enzymes. Under drought conditions, there was considerable upregulation of enzymes related to redox homeostasis, DHA reductase, Glyoxalase, SOD and isoflavone reductase. However, upregulation of catalase was not observed until after re-watering was carried out. Drought treatment caused an enhancement in antioxidant defense responses that can be modulated by ABA, and its catabolites, ABA-GE, as well as JA. Furthermore, quantification of protein carbonylation was shown to be a useful marker of the relationship between water and oxidative stress, and showed that there was only moderate oxidative stress in C. albidus plants subjected to water stress. After re-watering plants recovered although the levels of ABA-GE and antioxidant enzymes still remain higher than in well-watered plants. We expect that our results will provide new data on summer acclimation to drought stress in Mediterranean shrubs.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-014-2221-0) contains supplementary material, which is available to authorized users.
Highlights
Cistus albidus (Rockrose) is a semi-deciduous shrub that is highly acclimated to summer Mediterranean drought conditions
At least 10 individuals were used in each sampling point beginning of water stress (August 9), relative water content (RWC) decreased to 49 % and kept on decreasing progressively, reaching the lowest value (33 %) at the beginning of September
We examined the dynamics of the leaf proteome by simultaneously measuring the following parameters: gas exchange and stress markers such as maximum efficiency of photosystem II (PSII) photochemistry (Fv/Fm) and protein carbonylation; antioxidants such as ascorbate and glutathione; and hormones such as abscisic acid (ABA) and its metabolites, ABA-GE, PA, DPA and jasmonic acid
Summary
Cistus albidus (Rockrose) is a semi-deciduous shrub that is highly acclimated to summer Mediterranean drought conditions. Cell redox homeostasis and hormonal regulation responses to drought have been previously studied in this shrubs (Munne-Bosch et al 2001; Jubany-Marı et al 2009; Galle et al 2011); currently, large gaps still remain in the understanding of the different regulatory networks that control complex plant responses to the dynamic environment in which it grows (Luhua et al 2013). To the best of our knowledge, this is the first report to study simultaneously the dynamics of the leaf proteome alongside photosynthesis, antioxidants and plant hormones in C. albidus shrubs growing in their natural habitat and subjected to long-term summer drought stress. In spite of the fact that these methods only focus on one type of protein modification without taking into consideration all redox protein networks, the assessment of protein carbonylation can be used as an oxidative stress marker in plant cells (Johansson et al 2004)
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