OsLEA3-2 , an Abiotic Stress Induced Gene of Rice Plays a Key Role in Salt and Drought Tolerance Jianli Duan1,2, Weiming Cai1* 1 Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People’s Republic of China, 2 Graduate University of the Chinese Academy of Sciences, Beijing, People’s Republic of China Abstract Late embryogenesis abundant (LEA) proteins are involved in tolerance to drought, cold and high salinity in many different organisms. In this report, a LEA protein producing full-length gene OsLEA3-2 was identified in rice (Oryza sativa) using the Rapid Amplification of cDNA Ends (RACE) method. OsLEA3-2 was found to be only expressed in the embryo and can be induced by abiotic stresses. The coding protein localizes to the nucleus and overexpression of OsLEA3-2 in yeast improved growth performance compared with control under salt- and osmotic-stress conditions. OsLEA3-2 was also inserted into pHB vector and overexpressed in Arabidopsis and rice. The transgenic Arabidopsis seedlings showed better growth on MS media supplemented with 150 mM mannitol or 100 mM NaCl as compared with wild type plants. The transgenic rice also showed significantly stronger growth performance than control under salinity or osmotic stress conditions and were able to recover after 20 days of drought stress. In vitro analysis showed that OsLEA3-2 was able to protect LDH from aggregation on freezing and inactivation on desiccation. These results indicated that OsLEA3-2 plays an important role in tolerance to abiotic stresses. Citation: Duan J, Cai W (2012) OsLEA3-2, an Abiotic Stress Induced Gene of Rice Plays a Key Role in Salt and Drought Tolerance. PLoS ONE 7(9): e45117. doi:10.1371/journal.pone.0045117 Editor: Sunghun Park, Kansas State University, United States of America Received April 11, 2012; Accepted August 13, 2012; Published September 14, 2012 Copyright: 2012 Duan, Cai. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by the National Basic Research Program of China (grant 2011CB710902), the National Scientific Program (grant 2012AA101103-03), the National Natural Science Foundation of China (grant 90917009, 31070237), the Knowledge Innovation Program of the Chinese Academy of Sciences (grant KJCX2-YW-L08), the China Manned Space Flight Technology Project and the National Transgenic Program (grant 2009ZX08004-008B). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: wmcai@sibs.ac.cn Introduction Late embryogenesis abundant (LEA) genes code for a diverse group of proteins that accumulate to high levels in seed development [1]. LEA proteins play an important role in the maturation process of embryos and the accumulation of LEA proteins in embryos is correlated with the ability to tolerate desiccation [2]. The expression of LEA genes can be induced by the application of abscisic acid and by various abiotic stresses such as dehydration, osmotic stress, or cold in both reproductive and vegetative tissues [3,4,5,6,7,8]. LEA proteins of 5–9 different homology classes have been categorized based on similarities in their amino acid sequences and expression patterns [5,9,10,11]. The group of 3 LEA proteins are principally composed of tandem repeats of an 11-mer amino acid motif (TAQAAKEKAGE), forming an amphiphilic helical struc- ture [12]. Based on their structure characteristics, the group 3 LEA proteins have been suggested to function in binding or the replacement of water, in the sequestration of ions, and in the preservation of protein and membrane structure during de- hydration [5]. Group 3 LEA proteins, which are mostly cytosolic proteins [13], have been intensely analyzed in barley (Hordeum vulgare) [14], wheat (Triticum sp.) [15], cotton (Gossypium sp.) [12], rice (Oryza sativa) [7], maize (Zea mays) [16], and so on. The accumulation of the group 3 LEA transcript has been associated with genotypic differences in the acclimation to cold in rice varieties [17]. The expression of a group 3 LEA protein gene (HVA1) from barley has been shown to confer tolerance to water- and salt-stress in transgenic rice [18] and in transgenic mulberry [19]. Overexpression of a soybean group 3 LEA gene (PM2) confers the tolerance of in E. coli and stabilizes enzyme activity under diverse stresses [20]. Here, we report the isolation and functional characterization of the OsLEA3-2 gene (accession no. JQ043381), which encodes a group 3 LEA proteins in rice. A semi quantitative RT-PCR analysis revealed that the OsLEA3-2 gene does not express in vegetative tissues under normal conditions; however, it can be induced by abiotic stresses. To better understand the function of the OsLEA3-2 protein exposed to stresses conditions, S. cerevisiae cells that expressed OsLEA3-2 were produced and the growth was compared with S. cerevisiae cells harboring a pYES2 vector under salt and osmotic conditions. The OsLEA3-2 cells displayed improved growth as compared to the control strain under salt- and osmotic-stress. OsLEA3-2 overexpressing trans- genic Arabidopsis and rice showed significantly stronger growth performance than control under abiotic stresses. OsLEA3-2 was also able to protect lactate dehydrogenase (LDH) from aggregation on freezing and inactivation on desiccation in vitro. All this results indicate that OsLEA3-2 is conservative in resistance to abiotic stresses. PLOS ONE | www.plosone.org 1 September 2012 | Volume 7 | Issue 9 | e45117