pvSPS4 is involved in regulation of root sugar balance in common bean under salt stress

Salinity is a stress factor that decreases global agricultural yield. Crops such as rice, tomato, potato, and legumes are susceptible to salt, thus this problem requires urgent attention. Disruption of carbohydrate metabolism can have negative effects on stress tolerance. Sucrose phosphate synthase (SPS) enzymes operate in a key regulatory step in sucrose synthesis. Therefore, they have a significant role in the regulation of sugar metabolism. This study focused on the function of the SPS homolog -pvSPS4- in the roots of legume crop common bean under salinity stress. We previously showed that pvSPS4 expression is root-specific and is upregulated under salt stress in a salt-tolerant common bean genotype. This upregulation was accompanied by an accumulation of sugars in the roots. In the current study, using the same genotype, we generated composite common bean plants with wild-type shoot and pvSPS4 knock-down roots. Composite plants exhibited a more sensitive phenotype under salt stress compared to control and mock plants. pvSPS4 knock-down disturbed the root glucose/sucrose ratio and balance of Ca⁺², Mg⁺², and K⁺ in both root and leaves which resulted in a reduction in photosynthetic pigments together with osmoregulation and antioxidant capability. Our results imply that pvSPS4 is an important gene for carbohydrate balance regulation under salt-stress in the common bean root tissues and sets an example for the significance of mainly disregarded roles of SPS genes in sink tissues.