Identification of Membrane Proteins in Maize Leaves, Altered in Expression Under Drought Stress Through Polyethylene Glycol Treatment (Report‪)‬

Introduction Drought is a major environmental stress factor that affects the growth and development of plants and causes yields loss in cultivated crops worldwide (Waraich et al., 2011). The physiological and molecular basis for plant responses to drought has been the subject of intensive researches (Bartels and Sunkar 2005). To counter the effects of drought, plants undergo a process of stress acclimation. This process may require changes in gene (e.g. Gorantla et al. 2007, Guo et al. 2009, Harb et al. 2010) and protein expression profiles (e.g. Plomion et al. 2006, Bhushan et al. 2007, Aranjuelo et al. 2010). Membrane proteins in plants play a key role in various important cellular mechanisms, such as metabolite, ion transport and responses to biotic and abiotic stresses, etc, according to their location at the interface between cells or between cell compartments (Marmagne et al. 2004). Therefore, the analysis of membrane proteins is highly relevant to our understanding various phenomenon of life, including the mechanisms of stress tolerance. However, despite decades of extensive research, the large-scale analysis of membrane proteins remains a difficult task. This is due to the fact that membrane proteins require a carefully balanced hydrophilic and lipophilic environment, while most protein chemistry methods work mainly, if not only, in water-based media (Rabilloud et al., 2009). Although these limitations, a set of data is now available for membrane proteins using other tools, such as SDS-PAGE, 2D blue native/SDS-PAGE and chromatography etc. (Bell et al., 2001; Zhang et al., 2006; Klepsch et al., 2008). However, SDS-PAGE and 2D blue native/SDS-PAGE can only analyze a limited number of proteins compared with classical 2-DE. Conventional 2-DE remains a method of choice for analysis membrane proteins, at least, those more hydrophilic peripheral membrane proteins. Maize (Zea mays) is one of the most important food crops in the world. During the growing season, maize plants often encounter drought and high temperature stresses. In recently years, the physiological and molecular basis for plant responses to dehydration tolerance has been the subject of intense research (Flexas et al., 2002; 2009; Bhushan et al., 2007). At present, we focused to study the response to drought stress of maize (Hu et al., 2010; 2011). Although the effect of drought stress on protein expression in plants has been extensively studied, little is known about the changes of membrane proteome in plants under drought conditions. In plants, membrane proteomics was focused on plasma, chloroplast, mitochondria, etc. in Arabidopsis and rice (Komatsu 2008). The objectives of this study were to determine membrane protein changes of maize plants under drought stress and to provide new insights into maize drought response and resistance. Therefore, we carried out a differential proteome analysis to investigate the alterations of membrane protein expression in maize leaves in response to drought.