Journal of Plant Physiology 176 (2015) 36–46 Contents lists available at ScienceDirect Journal of Plant Physiology journa l h om epage: www.elsevier.com/locate/jplph Functional biotechnology A nuclear-localized histone-gene binding protein from rice (OsHBP1b) functions in salinity and drought stress tolerance by maintaining chlorophyll content and improving the antioxidant machinery Nita Lakra a , Kamlesh K. Nutan a , Priyanka Das a , Khalid Anwar a , Sneh L. Singla-Pareek b , Ashwani Pareek a,∗ a Stress Physiology and Molecular Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India b Plant Molecular Biology, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Road, New Delhi 110067, India a r t i c l e i n f o Article history: Received 15 September 2014 Received in revised form 15 November 2014 Accepted 17 November 2014 Available online 6 December 2014 Keywords: Drought OsHBP1b Rice Salinity Transcription factor a b s t r a c t Plants have evolved a number of molecular strategies and regulatory mechanisms to cope with abiotic stresses. Among the various key factors/regulators, transcription factors (TFs) play critical role(s) towards regulating the gene expression patterns in response to stress conditions. Altering the expression of the key TFs can greatly influence plant stress tolerance. OsHBP1b (accession no. KM096571) is one such TF belonging to bZIP family, localized within the Saltol QTL, whose expression is induced upon salinity treat- ment in the rice seedlings. qRT-PCR based expression studies for OsHBP1b in seedlings of contrasting genotypes of rice showed its differential regulation in response to salinity stress. A GFP based in vivo study showed that the OsHBP1b protein is nuclear localized and possesses the trans-activation activity. As compared to the WT tobacco plants, the transgenic plants ectopically expressing OsHBP1b showed better survival and favourable osmotic parameters (such as germination and survival rate, membrane stability, K + /Na + ratio, lipid peroxidation, electrolyte leakage and proline contents) under salinity and drought stress. Under salinity conditions, the transgenic plants accumulated lower levels of reactive oxy- gen species as compared to the WT. It was also accompanied by higher activities of antioxidant enzymes (such as ascorbate peroxidase and superoxide dismutase), thereby demonstrating that transgenic plants are physiologically better adapted towards the oxidative damage. Taken together, our findings suggest that OsHBP1b contributes to abiotic stress tolerance through multiple physiological pathways and thus, may serve as a useful ‘candidate gene’ for improving multiple stress tolerance in crop plants. © 2014 Elsevier GmbH. All rights reserved. Introduction The basic-leucine zipper (bZIP) protein family is one of the largest families of transcription factors (TFs) that contain a highly conserved bZIP domain with two structural features: a basic domain responsible for sequence-specific DNA-binding and a leucine zipper domain (Lee et al., 2006). These proteins are present throughout the plant kingdom and are reported to be involved in a variety of physiological processes including seed-maturation and germination, flower-development, fertility (Zou et al., 2008; Alves Abbreviations: HBP, histone-gene binding protein; TF, transcription factor; ABA, abscisic acid; bZIP, basic-leucine zipper; MDA, malondialdehyde; ROS, reactive oxy- gen species; SOD, super oxide dismutase; APX, ascorbate peroxidase; CAT, catalase. ∗ Corresponding author. Tel.: +91 11 26704504; fax: +91 11 26742558. E-mail address: ashwanip@mail.jnu.ac.in (A. Pareek). et al., 2013), plant-senescence (Lee et al., 2006), responses to var- ious abiotic stresses and abscisic acid (ABA), and stress signalling (Nijhawan et al., 2008). Though, plants which are over-expressing bZIP proteins have been reported to exhibit higher tolerance to salinity and freezing stress (Liao et al., 2008), oxidative stress (Lee et al., 2006), drought, and high temperature stress (Zhang et al., 2008), their physiological and molecular basis of tolerance is yet to be worked out. The gene expression data based on microarrays and RNA blots has clearly established the fact that salinity tolerance of a toler- ant cultivar of rice may be due to constitutive high expression of various genes that take part in salinity tolerance. Based on the transcriptome analysis carried out in our lab, it has been reported that, the salt-tolerant cultivar—Pokkali maintains higher transcript levels under unstressed conditions as a possible strategy for adap- tation to salinity stress (Kumari et al., 2009). In addition, it has also been reported that a set of shortlisted genes present in Saltol QTL http://dx.doi.org/10.1016/j.jplph.2014.11.005 0176-1617/© 2014 Elsevier GmbH. All rights reserved.