Constitutive expression of Arabidopsis bZIP transcription factor AREB1 activates cross-signaling responses in soybean under drought and flooding stresses.

Abiotic stress, such as drought and flooding, are responsible for considerable losses in grain production worldwide. Soybean, the main cultivated oilseed in the world, is sensitive to both stresses. Plant molecular mechanisms answer via crosstalk of several signaling pathways, in which particular genes can respond to different stresses. Previous studies confirmed that overexpression of transcription factor AtAREB1 confers drought tolerance in soybean. However, plants containing this gene have not yet been tested under flooding. Thus, the objective of this study was to characterize genetically modified (GM) soybean plants overexpressing AtAREB1 under drought and flooding conditions in comparison to its genetic background. Physiological and biochemical measurements were performed. In addition, the expression level of genes commonly activated under both stresses was evaluated. The results supported the role of the AtAREB1 gene in conferring tolerance to water deficit in soybeans. Furthermore, under flooding, the GM line was efficient in maintaining a higher photosynthetic rate, intrinsic efficiency in water use, and instantaneous carboxylation efficiency, resulting in higher grain yield under stress. The GM line also presented higher protein content, lower concentration of hydrogen peroxide, and lower expression levels of genes related to fermentative metabolism and alanine biosynthesis. These results indicate that in addition to drought stress, plants overexpressing AtAREB1 exhibited better performance under flooding when compared to the non-GM line, suggesting a cross-signaling response to both abiotic factors.