Response of proteome and morphological structure to short-term drought and subsequent recovery in Cucumis sativus leaves

Drought is the primary limitation to plant growth and yield in agricultural systems. Cucumber (Cucumis sativus) is one of the most important vegetables worldwide and has little tolerance for water deficit. To understand the drought stress response strategy of this plant, the responses of cucumber to short-term drought and rewatering were determined in this study by morphological structure and proteomic analyses. The leaf relative water content was significantly decreased under drought, and the cell structure was altered, while rewatering obviously alleviated the symptoms of water shortage and cell damage. A total of 320 and 246 proteins exhibiting significant abundance changes in response to drought and recovery, respectively, were identified. Our proteome analysis showed that 63 co-regulated proteins were shared between drought and rewatering, whereas most of the responsive proteins were unique. The proteome is adjusted through a sequence of regulatory processes including the biosynthesis of secondary metabolites and the glutathione metabolism pathway, which showed a high correlation between protein abundance profile and corresponding enzyme activity. Drought and recovery regulated different types of proteins, allowing plants to adapt to environmental stress or restore growth, respectively, which suggests that short-term drought and recovery are almost fully uncoupled processes. As an important component of the antioxidant system in plants, glutathione metabolism may be one of the main strategies for regulating antioxidant capacity during drought recovery. Our results provide useful information for further analyses of drought adaptability in cucumber plants.