BIOLOGIA PLANTARUM 53 (1): 145-150, 2009 145 BRIEF COMMUNICATION Differential expression of LEA proteins in two genotypes of mulberry under salinity G. JYOTHSNAKUMARI*, M. THIPPESWAMY**, G. VEERANAGAMALLAIAH** and C. SUDHAKAR*** 1 Department of Botany, Acharya Nagarjuna University, Nagarjuma Nagar-522510, India* Department of Botany** and Biotechnology***, Sri Krishnadevaraya University, Anantapur-515003, India Abstract The relative water content (RWC), cell membrane integrity, protein pattern and the expression of late embryogenesis abundant proteins (LEA; group 1, 2, 3 and 4) under different levels of salt stress (0, 1.0, 1.5 and 2.0 % NaCl) were investigated in mulberry (Morus alba L.) cultivars (S1 and ATP) with contrasting salt tolerance. RWC and membrane integrity decreased with increase in NaCl concentration more in cv. ATP than in cv. S1. SDS-PAGE protein profile of mulberry leaves after the NaCl treatments showed a significant increase in 35, 41, 45 and 70 kDa proteins and significant decrease in 14.3, 18, 23, 28, 30, 42, 47 and 65 kDa proteins. Exposure of plants to NaCl resulted in higher accumulation of LEA proteins in S1 than ATP. The maximum content of LEA (group 3 and 4) was detected in S1 at 2.0 % NaCl, which correlates with its salt tolerance. Additional key words: cell membrane stability, Morus alba, NaCl stress, RWC. ⎯⎯⎯⎯ Plants have developed different mechanisms to withstand salt stress (Niknam et al. 2006, Sotiropoulos et al. 2007, Melgar et al. 2008). These include alterations in the content of numerous proteins and mRNAs. Exposure of plants to high salinity increases the gene expression for protective proteins such as osmotin, late embryogenesis abundant (LEA) proteins, pathogenesis related (PR) proteins, ion transporters and SALT proteins (Moons et al. 1997a,b, De Souza et al. 2003, Jyothsnakumari 2005, Rorat 2006). LEA proteins were firstly observed in cotton and wheat during embryogenesis and germination (Dure et al. 1981). LEA proteins have been identified in many plant species, and at least six different groups of LEA proteins have been defined on the basis of expression pattern and amino acid sequence, among these the major categories are group 1, group 2 and group 3. Group 1 LEA proteins have been sub-divided into two super families and are found only in plants (Wise 2003). Group 2 LEA are an abundant and diverse family of proteins that are synthesized in response to salinity, drought and dehydra- tion stress including low/freezing temperatures and are mainly found in plants (Svensson et al. 2002, Allagulova et al. 2003, Cherian et al. 2006, Wahid and Close 2006). Group 2 LEA (dehydrins, DHN, or responsive to abscisic acid, RAB proteins) have also been predicted to function as chaperones useful for maintaining protein structure and function. The group 3 LEA proteins, comprising of two super families are characterized by repeated 11-mer amino acid motif. LEA 3 is known to counteract the irreversible damaging effects of increased ionic strength in cytosol during desiccation by sequestration of ions (Dure 1993). The group 4 LEA proteins are suggested to bind water molecules and may also act as chaperones, whereby these would stabilize the surface of membranes and possibly proteins by binding water and functioning as solvation film. It has been reported that genes encoding group 4 LEA are expressed in vegetative tissues in ⎯⎯⎯⎯ Received 24 April 2007, accepted 24 November 2007. Abbreviations: ABA - abscisic acid; DHN - dehydrin; LEA - late embryogenesis abundant; PR - pathogen related; RAB - responsive to ABA; SDS-PAGE - sodium dodecyl sulfate polyacrylamide gel electrophoresis. Acknowledgements: GJK is grateful to Council of Scientific and Industrial Research, New Delhi for the SRF award (CSIR No. 9/383(38)2K3-EMR-I). Part of this study was supported by a research grant (F. 31-161/2005) to CS by the UGC, New Delhi. We thank Prof. M. Udaykumar for the gift of group 1, 2, 3 and 4 LEA antisera. Authors are thankful to the authorities of RSRS, Anantapur for providing mulberry germplasm cuttings. We deeply condole the sudden demise of Dr. G. Jyothsnakumari. We know that her passing will not only leave a void in our research, but in the hearts of all those who knew her. Dr. Kumari will always remain within our hearts and we dedicate this article to Dr. G. J. Kumari. 1 Corresponding author; fax: (+91) 08544 255054, e-mail: chintasudhakar@yahoo.com