Universal Stress Protein Gene (SlUSP1) Confers Drought Tolerance In Tomato

Drought is the major abiotic stress affecting plant growth and development. According to recent statistics, drought brings the losses to agricultural production is equal to the sum losses by other biotic and abiotic stress. Traditional breeding methods are time and labor-consuming with low efficiency to improve crops tolerance to drought. To get drought tolerance crops and understand their mechanisms, drought stress has been studied on the base of morphological, physiological and biochemical, and later at molecular level. For molecular study, over a hundred of genes were identified and cloned, and they were classified into two major groups:(1) genes encode structural proteins, and (2) genes encode regulatory proteins.Tomato (Solanum lycopersicum) is one of the most important economical vegetable crops in the Solanaceae family and also has been used as a model system. In our previous study, we applied microarray analysis on two drought-tolerant introgression lines containing chromosome segments of wild tomato species (S. pennellii) and identified a large set of drought-responsive genes, including a gene encoding universal stress protein (USP). In this study, the above-mentioned gene, designated S1USP1, was cloned and functionally characterized. The main results are as follows:1. SIUSP1was cloned from tomato genome and sequenced, which encoded a novel universal stress protein with134amino acids.2. Expression profile analysis using quantitative RT-PCR showed that SIUSP1transcript was abundant in leaf tissue, and it was produced maximally in the afternoon. The gene was induced by different abiotic stresses such as dehydration, cold and hormones like abacisic acid (ABA).3. Overexpression vectors of SIUSP1were transformed into tomato cultivar ZS6via Agrobacterium-mediated transformation, and total of25transgenic plants were obtained.4. Abiotic stress tolerance assays were applied on three SlUSO1-overexpressing lines. Results from both germination and seedling experiments demonstrated that overexpression of SlUSP1improved tomato drought tolerance.5. Several proteins, including an annexin (Tomato unigene database identifier:SGN-U314161) were found to interact with SlUSP1in yeast two-hybrid screenings, and the interaction was further confirmed by using bimolecular fluorescence complementation assay.