Galactinol synthase confers salt-stress tolerance by regulating the synthesis of galactinol and raffinose family oligosaccharides in poplar

Plants respond to abiotic stress through a series of transcriptional profile and metabolic process modifications through signaling events. Raffinose family oligosaccharides (RFOs) play a role in the regulatory mechanisms of abiotic stress tolerance and are catalyzed by the key enzyme, galactinol synthase (GolS), in plants. The amino acids sequences of GolS of Populus trichocarpa contained the common features of GolS proteins in other plant species, namely, a hydrophobic pentapeptide (APSAA). The PtrGolS3 promoter region contains several cis-elements for stress responses, including abscisic acid responsive element (ABRE), the dehydration and cold responsive elements (DRE/CRT), the low-temperature responsive element (LTRE), and the transcription factor MYB binding sites. Overexpression of AtGolS2 and PtrGolS3 enhanced abiotic stress tolerance along with the expression of stress-related genes in transgenic poplar. In addition, overexpression of AtGolS2 and PtrGolS3 resulted in higher contents of soluble sugars and other stress-associated metabolites (proline, salicylic acid, phenylalanine, and so forth) in two GolS overexpressing poplar lines compared with wild-type poplar under salt stress. Based on these results, a promising PtrGolS candidate gene for metabolic engineering of sugars to improve abiotic stress tolerance in poplar was identified and it may increase the understanding of RFO metabolism in woody plants under short-term salt treatment.

Automated summary

Plants respond to abiotic stress through transcriptional and metabolic adjustments, with Raffinose family oligosaccharides (RFOs) and the key enzyme galactinol synthase (GolS) playing crucial roles. The GolS of Populus trichocarpa shares common features with GolS proteins in other plants and contains stress-responsive elements in its promoter region. Overexpressing AtGolS2 and PtrGolS3 in poplar enhances stress tolerance and increases the accumulation of stress-related metabolites, suggesting these genes as potential candidates for improving abiotic stress tolerance in woody plants.