Proteomics of ionic stresses in rice: An overview

Abstract Ions deficiency or excess remains one of the critical ground level environmental problems, affecting crop productivity. In this overview, we will discuss an increased application of proteomics technology in addressing this issue using rice ( Oryza sativa L.) as a model crop plant. Proteomics analyses have revealed that rice proteome unde-rgoes changes in the proteins composition and expression in response to several ionic stresses, including mineral nutrients (aluminum, nitrogen, and phosphorous) and heavy metals (arsenic, cadmium, and copper). Developed inventory of responsive proteins and their correlation with changes in physiological symptoms and parameters are a major step forward in: (i) better understanding the underlying mechan-isms of ionic stresses-triggered responses in rice; (ii) comparative proteomics studies; and (iii) designing a novel strategy to improve crop plants. Keywords Ionic stress, rice, proteomics Introduction Rice ( Oryza sativa L.) is a major edible crop contrib-uting directly to growth and development of the human civilization in Asia by providing a source of nourishment in an easily utilizable form, namely the seed. However, its growth and grain (or seed) yield are dramatically affected by adverse environmental stresses (Agrawal et al. 2006, 2009; Agrawal and Rakwal 2006, 2008b, 2011). Heavy metals and excessive use of fertilizers are one of the growing environmental problems. Heavy metals are alone responsible for soil pollution of about 235 million hectares (Giordani et al. 2005). To study the effects of such pollutants is a major area of research in plant biology. Proteomics technology has increasingly been utilized to understand the impact of environmental stresses on changes in the rice proteome, resulting in development of an inventory of responsive proteins (see a series of reviews, Agrawal et al. 2006, 2009; Agrawal and Rakwal 2003, 2006, 2008b, 2011). Such inventory has helped in constructing a working model and biology-driven hy-pothesis to overcome the environmental problems, including the ionic stresses. Ionic stress can be considered as an environmental problem that is by and large man-made. Therefore, it is ironic that we are now working hard to understand the effects of these stresses. In this regard, omics technologies including proteomics play a major role. Identified proteins are being used as potential biomarkers in dissecting the signaling and metabolic pathways responsive to ionic stresses and in crop breeding programs (see, Agrawal and Rakwal 2008a).To date, there are nine proteomics-level studies, dealing with ionic stresses-triggered responses in rice. Those studies include aluminum (Al; Yang et al. 2007), nitrogen (N; Kim et al. 2009; Kim et al. unpublished results), phosphorous (P; Torabi et al. 2009), arsenic (As; Ahsan et al. 2008), cadmium (Cd; Aina et al. 2007; Lee et al.