pvSPS4 is Crucial for the Root Sugar Balance and Proper Tolerance Response in Salt-Tolerant Common Bean Genotype Under Salt Stress

Abstract

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. Stress-related carbohydrate metabolism is a dynamic network of genetic and metabolic pathways. Disruption in the regulation of soluble sugar content can have negative effects on source-sink partitioning. As source-sink partitioning is connected to the supply, and distribution of energy in the plant, it is critical for stress tolerance. Sucrose phosphate synthase (SPS) enzymes operate in a key regulatory step in sucrose synthesis. Therefore, they have a significant role in sugar metabolism including the regulation of source-sink sucrose transportation. 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 increased sensitivity to salt stress compared to control and mock plants. pvSPS4 knock-down disturbed the root glucose/sucrose ratio and ionic balance 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 as a salt-stress response in the common bean root tissues.