Abstract
About 1000 salt-responsive ESTs were identified from an extreme halophyte Salicornia brachiata. Among these, a novel salt-inducible gene SbSLSP (Salicornia brachiata SNARE-like superfamily protein), showed up-regulation upon salinity and dehydration stress. The presence of cis-regulatory motifs related to abiotic stress in the putative promoter region supports our finding that SbSLSP gene is inducible by abiotic stress. The SbSLSP protein showed a high sequence identity to hypothetical/uncharacterized proteins from Beta vulgaris, Spinacia oleracea, Eucalyptus grandis, and Prunus persica and with SNARE-like superfamily proteins from Zostera marina and Arabidopsis thaliana. Bioinformatics analysis predicted a clathrin adaptor complex small-chain domain and N-myristoylation site in the SbSLSP protein. Subcellular localization studies indicated that the SbSLSP protein is mainly localized in the plasma membrane. Using transgenic tobacco lines, we establish that overexpression of SbSLSP resulted in elevated tolerance to salt and drought stress. The improved tolerance was confirmed by alterations in a range of physiological parameters, including high germination and survival rate, higher leaf chlorophyll contents, and reduced accumulation of Na+ ion and reactive oxygen species (ROS). Furthermore, overexpressing lines also showed lower water loss, higher cell membrane stability, and increased accumulation of proline and ROS-scavenging enzymes. Overexpression of SbSLSP also enhanced the transcript levels of ROS-scavenging and signaling enzyme genes. This study is the first investigation of the function of the SbSLSP gene as a novel determinant of salinity/drought tolerance. The results suggest that SbSLSP could be a potential candidate to increase salinity and drought tolerance in crop plants for sustainable agriculture in semi-arid saline soil.
Highlights
The human population is growing rapidly and expected to be more than 9 billion by 2050 (Godfray et al, 2010)
The NCBI protein blast analysis revealed that the SbSLSP protein has a high sequence identity (78–95%) to a SNARElike superfamily protein and/or hypothetical uncharacterized proteins from different plant species
Phylogenetic analysis revealed that SbSLSP showed close neighborhood with other Amaranthaceae family members B. vulgaris and S. oleracea, which is suggesting the evolutionary conservation within the family
Summary
The human population is growing rapidly and expected to be more than 9 billion by 2050 (Godfray et al, 2010). The environmental factors affecting crop yield are mainly grouped as biotic and abiotic stresses. Drought, high temperature, waterlogging, high light intensity and the mineral deficiency are the major abiotic stresses which negatively affects plant growth, resulting in reduced yield or may leads to death of the plants at extreme conditions (Mahajan and Tuteja, 2005). These stresses are responsible for reducing yield by more than 50% of major crops across the globe (George et al, 2012). The roles of many stress responsive genes and micro RNAs and few of the cis- and trans- regulatory factors have been studied in stress tolerance (Yamaguchi-Shinozaki and Shinozaki, 2006; Agarwal and Jha, 2010; Nakashima et al, 2012; Singh and Jha, 2014)
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