Abstract

Reactive oxygen species (ROS) are generated as by-products of fundamental metabolic processes such as photosynthesis and cellular respiration, and their accumulation increases under abiotic stress conditions and during leaf senescence. Lipoic acid (LA) is a multifunctional antioxidant that neutralizes ROS, regenerates other antioxidants, and acts as a cofactor of key enzymes in energy metabolism. On the other hand, ethylene is a phytohormone that regulates processes such as senescence and fruit ripening. Both molecules share S- adenosylmethionine (SAM) as a biosynthetic precursor, suggesting a potential competition for this metabolite and a cross-regulation between their metabolic pathways.

We investigated the interaction between the biosynthetic pathways of LA and ethylene through exogenous applications of LA, transgenic lines with increased LA production in fruits, and the use of inhibitors of ethylene biosynthesis (aminoethoxyvinylglycine, AVG) and perception (1-methylcyclo propene, 1-MCP) in MicroTom tomato (Solanum lycopersicum) plants.

LA application promoted the expression of antioxidant and ethylene-related genes, enhancing antioxidant capacity and ethylene production in senescent leaves and ripening fruits. Transgenic lines also exhibited transcriptional induction, although without significant increases in antioxidant capacity. On the other hand, inhibition of ethylene biosynthesis by AVG led to an increase in lipoylated proteins, an effect not observed with 1-MCP. This supports the hypothesis that ethylene biosynthesis, rather than perception, modulates this metabolic competition. These findings open new perspectives for the development of biotechnological strategies aimed at optimizing key processes such as fruit ripening and leaf senescence through the coordinated manipulation of LA and ethylene metabolism.

Funding: ANID Fondecyt 1231417 (MH), Fundación María Ghilardi Venegas (MPC) and ANID Doctoral Scholarship (21210768, FU).