Calcium-dependent changes in physicochemical properties and the proteome dynamics influence dehydration responses in rice

Abstract

The cytosolic Ca2+ ([Ca2+]cyt), in plants serves as secondary messenger during development and stress adaptive responses. While several of the components of Ca2+-signalling, especially involved in water-deficit stress or dehydration are known, the underlying mechanism of such regulations remain poorly understood. In this study, we investigated the Ca2+-mediated alleviation of dehydration stress in rice. The physicochemical indices of the rice seedlings pretreated with CaCl2, followed by dehydration treatment displayed better maintenance of relative water content (RWC) and cell membrane integrity, besides peroxide levels. CaCl2-pretreated seedling showed stimulation of antioxidants contributing to long-term survival under dehydration stress. Contrastingly, blocking of Ca2+-channels aggravated the dehydration-induced damage, suggesting a crucial role of Ca2+-signalling in stress adaptation. The cytosolic proteome profiling of CaCl2-pretreated seedlings revealed 100 distinct proteins that include 56 dehydration-responsive proteins (DRPs), presumably involved in adaptive responses. A critical screening of the proteome led to the identification of a MADS-box transcription factor family protein, designated OsMADS23. The predicted structure and nuclear localization indicated that OsMADS23 might bind to nucleic acids, suggesting its possible role in transcriptional regulation. The stimulation of stress-responsive expression of OsMADS23 by Ca2+ demonstrated its participation in Ca2+-dependent signalling. Altogether, these results indicate the Ca2+-dependent dehydration response in plants and substantiate the function of a MADS-box protein in the cross-talk of developmental and stress-responsive pathways.