The interplay between sugar and ROS: sugar nature and its concentrations as determinants of the redox state in Arabidopsis thaliana

PAROLA R; LANDO A; MARTÍNEZ NOËL G; RODRIGUEZ M

Congreso; SAIB 2022; 2022

Sugars, in addition to being energy resources in plants, are important signaling molecules that regulate development and responses to environmental stresses. Sucrose (Suc) is the main sugar for systemic transport and a specific signaling pathway for this disaccharide has been described. Furthermore, glucose (Glc) has been shown to have sensing and signaling pathways that could be hexokinase dependent or independent. Noticeably, high sugar concentrations, resembling some stress conditions, could act as reactive oxygen species (ROS) scavengers or ROS producers. In this regard, we studied different types and concentrations of sugars on ROS homeostasis and growth in the model plant Arabidopsis thaliana. We performed the sugar treatments under dark conditions to avoid light effects. The results showed that sugars differentially affected the ROS state and antioxidant system at high concentrations (3 and 5%). Although seedlings treated with both Glc and Suc showed high levels of superoxide ion, they presented opposite responses mainly at the reduction power measured through FRAP assay and cell damage estimated by malondialdehyde content (MDA). The treatments with exogenous Suc at 5% showed a higher content of MDA and a lower reducing power than those with Glc at the same concentration. Regarding the enzymes of the antioxidant system, we observed increases in catalase (CAT) activity at high concentrations of both sugars. The total activity of the superoxide dismutase (SOD) enzyme increased slightly in seedlings treated with Glc and Suc at 5% compared to the control without sugar. However, the distinct SOD isoforms (CuZn, Mn and Fe) exhibited differential behavior. In particular, we observed a significant increase in activity of the isoforms Fe-SOD and CuZn-SOD in seedlings grown in Suc 3-5% and Glc 5%, respectively. These results demonstrate that there is an interplay between sugar nature and concentration with the generation of different types of ROS, their levels and subcellular localization. Associated with this, root growth was negatively affected at Glc 5% while seedlings treated with the same concentration of Suc continued growing. Altogether, Suc maintains ROS homeostasis and promotes growth, even when present at high concentrations, whereas elevated levels of Glc seem to produce oxidative damage despite inducing antioxidant systems. More research is needed to unveil the roles of ROS in the molecular mechanism behind the sugar responses.Palabras clave: Sugars, ROS homeostasis, Redox state