Abstract
Thioredoxins (Trxs) are multi-functional redox proteins characterized by a conserved redox-active CGPC site. In plants, Trxs are small antioxidant proteins encoded by a multigene family and regulate several processes during development and growth. Consequently, Thrxs are attractive candidates for transgenic plant improvement to overcome the abnormal plant growth and development observed during abiotic stress conditions. Here, we isolated the gene encoding the h-type Trx protein, LmTrxh2, from the halophyte plant Lobularia maritima and developed transgenic tobacco plants that overexpress LmTrxh2. Based on an in silico sequential, phylogenetic, and three-dimensional model analysis, LmTrxh2 protein shares high sequence identity and common structural characteristics with plant thioredoxins. RT-qPCR analysis revealed differential temporal and spatial regulation of LmTrxh2 in L. maritima exposed to salt (150 mM NaCl), osmotic (10% PEG 8000), and oxidative (10 mu M H2O2) stresses. Subcellular localization using confocal microscopy revealed that LmTrxh2 localized to the plasma membrane. Transgenic LmTrxh2 tobacco lines exhibited improved salt and osmotic stress tolerance compared to non-transgenic (NT) plants, and this tolerance was associated with mitigation of oxidative damage. Finally, four stress-related genes were upregulated in LmTrxh2 transgenic tobacco plants compared to those in NT plants under control and stress conditions. These findings suggest that LmTrxh2 is an attractive candidate gene for the genetic engineering of crops with enhanced salt and osmotic stress tolerance.