Short communication Proteomics reveals elevated levels of PR 10 proteins in saline-tolerant peanut (Arachis hypogaea) calli Shalu Jain a,1 , Sanjeeva Srivastava b,1 , Neera Bhalla Sarin a , Nat N.V. Kav b, * a School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067, India b Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada Received 8 November 2005 Available online 15 May 2006 Abstract The proteome of a salinity-tolerant Arachis hypogaea L. callus cell line was compared with its sensitive counterpart. Several low molecular weight proteins were detected by two-dimensional electrophoresis as being unique or significantly elevated in the tolerant line. The identities of several of these proteins were established as PR 10 proteins using tandem Mass Spectrometry and are shown to be phosphorylated on the basis of staining with the phosphorylation-specific stain, Pro-Q Diamond. Our results suggest that these differentially phosphorylated PR 10 proteins may play an important role in mediating salinity stress responses. © 2006 Elsevier SAS. All rights reserved. Keywords: Arachis hypogaea; Callus; Electrospray ionization; Pathogenesis related (PR) proteins; Phosphorylation; Salinity; Tandem mass spectrometry 1. Introduction Environmental stresses such as drought and salinity severely limit agricultural productivity by reducing average crop yield by more than 50% [1]. Salinity is particularly a global concern due to the widespread salinization of soils, which is estimated to reach a staggering 50% of all arable land by the year 2050 [2]. Salinity-induced damage to plants include membrane dis- organization, increase in levels of toxic metabolites, inhibited nutrient uptake and photosynthesis, generation of reactive oxy- gen species (ROS) and ultimately cell and plant death [3]. Due to this intricate and complex nature of plant responses to sali- nity, the quest for salinity-tolerant plants that are generated via conventional breeding has remained largely unsuccessful [4] whereas, biotechnological approaches have had some success [5,6]. The relatively homogenous population of cells provided by in vitro cultures of plant cells offers an excellent system to investigate the effects of salinity stress. Furthermore, the growth of plant cells in culture under prolonged salinity stress often results in tolerance and therefore may offer clues as to the molecular mechanisms that may be crucial to the development of tolerance [7–9]. In today’s post-genomic era, techniques that investigate changes in the protein component of the genome, i.e. the proteome, are being increasingly used in various disci- plines in order to investigate molecular changes that occur in response to stresses [10–12]. In this report we describe the characterization of proteome-level differences between a sali- nity-tolerant (ST) and –sensitive (SS) callus cell lines of Ara- chis hypogaea with a view of further understanding the mole- cular differences between the two lines that may be responsible for the higher tolerance to NaCl. 2. Results and discussion A salinity-tolerant cell line of Arachis hypogaea cv. JL 24 has been obtained by exposing the callus cells to NaCl as pre- viously described [9] and the tolerant cell line (ST) appears to grow better on NaCl than the sensitive lines (SS). Appearance of the SS and ST lines cultured on semi-solid media are shown in Fig. 1A and the effects of NaCl on fresh weight of both lines are shown in Fig. 1B. It is evident that the ST line appears to be healthier than the SS line at high concentrations of NaCl and is supported by the increased gain in fresh weight of the www.elsevier.com/locate/plaphy Plant Physiology and Biochemistry 44 (2006) 253–259 * Corresponding author. Tel.: +780 492 7584; fax: +780 492 4265. E-mail address: nat@ualberta.ca (N.N.V. Kav). 1 These authors contributed equally to this work. 0981-9428/$ - see front matter © 2006 Elsevier SAS. All rights reserved. doi:10.1016/j.plaphy.2006.04.006