Overexpression of the ABA-Dependent AREB1 Transcription Factor from Arabidopsis thaliana Improves Soybean Tolerance to Water Deficit

Among current strategies for the development of drought-tolerant plants, engineering transcription factors that regulate the expression of genes related to abiotic stress is promising. Soybean plants overexpressing the transcription factor AtAREB1, which is involved in abscisic acid (ABA)-dependent stress responses, were generated using biolistics. Embryos of cultivar BR16, which is considered drought sensitive, were co-transformed with two plant expression vectors, 35S::AtAREB1 and 35S::ahas. Among the lines obtained, the drought tolerance of A24.10 and A2889.12 was assessed because these lines overexpressed the AtAREB1 gene and had a low copy number of the transgene. Another line, A2057.03, was also selected because it had a high copy number of the transgene (more than 100 copies) and low levels of transgene expression. Among the two low-copy lines, the A24.10 plants exhibited a slightly lower number of leaves and a shortening of the internode length; however, no growth retardation was observed for the line A2057.03. Water stress tolerance was particularly improved in the low-copy lines A24.10 and A2889.12. Plants of these lines were able to survive a water stress period of 5 days and exhibited no leaf damage, i.e., dried areas in the leaves 3 days after rewatering. Furthermore, these lines exhibited better growth and physiological performance under water-deficit (higher relative rate of shoot length, stomatal conductance, and photosynthesis) when compared to the wild type. Our results show the potential for improving drought tolerance by overexpressing AtAREB1 in soybean.