INVESTIGATING THE ROLE OF REACTIVE OXYGEN SPECIES IN FRUIT RIPENING AND SENESCENCE

Abstract

Reactive oxygen species (ROS) play a pivotal yet complex role in fruit ripening and senescence, functioning both as essential signaling molecules and agents of oxidative damage. This study aimed to investigate the biochemical and molecular dynamics of ROS accumulation and antioxidant responses across different ripening stages in climacteric (tomato) and non-climacteric (strawberry) fruits. A combination of spectrophotometric assays, enzymatic activity quantification, histochemical staining, and gene expression profiling via qRT-PCR and RNA sequencing was employed. Results showed a significant increase in H₂O₂ and O₂⁻ concentrations during ripening, particularly in tomatoes, accompanied by elevated activities of key antioxidant enzymes—superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). Lipid peroxidation, measured by malondialdehyde (MDA) levels, also increased progressively, confirming rising oxidative stress as fruits matured. Gene expression analysis revealed ripening-specific upregulation of ROS-related genes (SlRboh1, SlAPX2, FaCAT1) and transcriptional regulators such as FaMYB10, with expression levels correlating strongly with biochemical markers. Notably, correlation analysis identified significant associations between ROS concentrations and antioxidant enzyme activities (r > 0.85, p < 0.001), indicating a tightly regulated oxidative balance essential for controlled ripening. Differences between fruit types highlighted species-specific ROS regulatory mechanisms, with climacteric fruits showing more pronounced oxidative changes. These findings establish ROS as central components in the physiological and molecular orchestration of fruit ripening and suggest their potential as biomarkers or targets for postharvest quality management. This research contributes critical insights into oxidative signaling pathways, paving the way for advanced strategies in crop storage, shelf-life extension, and genetic improvement.