Identification of extracellular matrix proteins of rice (Oryza sativa L.) involved in dehydration-responsive network: a proteomic approach.

Water-deficit or dehydration impairs almost all physiological processes and greatly influences the geographical distribution of many crop species. It has been postulated that higher plants rely mostly on induction mechanisms to maintain cellular integrity during stress conditions. Plant cell wall or extracellular matrix (ECM) forms an important conduit for signal transduction between the apoplast and symplast and acts as front-line defense, thereby playing a key role in cell fate decision under various stress conditions. To better understand the molecular mechanism of dehydration response in plants, four-week-old rice seedlings were subjected to progressive dehydration by withdrawing water and the changes in the ECM proteome were examined using two-dimensional gel electrophoresis. Dehydration-responsive temporal changes revealed 192 proteins that change their intensities by more than 2.5-fold, at one or more time points during dehydration. The proteomic analysis led to the identification of about 100 differentially regulated proteins presumably involved in a variety of functions, including carbohydrate metabolism, cell defense and rescue, cell wall modification, cell signaling and molecular chaperones, among others. The differential rice proteome was compared with the dehydration-responsive proteome data of chickpea and maize. The results revealed an evolutionary divergence in the dehydration response as well as organ specificity, with few conserved proteins. The differential expression of the candidate proteins, in conjunction with previously reported results, may provide new insight into the underlying mechanisms of the dehydration response in plants. This may also facilitate the targeted alteration of metabolic routes in the cell wall for agricultural and industrial exploitation.