Lipoic acid (LA) plays an important role in primary metabolism as a cofactor for various enzyme complexes, including the E2 subunits of pyruvate dehydrogenase (PDH) and alpha-ketoglutarate dehydrogenase (kGDH). Although often overlooked, LA has gained renewed interest recently because of its strong antioxidant properties and use as a dietary supplement. Researchers have discovered how LA is synthesized in living organisms, identifying lipoyl synthase (LIP1) as the essential enzyme for this process.
In this study, the researchers used the fruit-specific polygalacturonase (PG) promoter to direct the overexpression of the Solanum lycopersicum (tomato) LIP1 (SlLIP1) gene in genetically modified tomato plants.
The modified plants showed higher levels of SlLIP1 transcripts specifically in the fruit, accumulated more bound and unbound LA, and did not exhibit significant defects in either vegetative or reproductive growth stages. Additionally, the researchers examined changes in the expression of genes related to LA synthesis and conducted a metabolomic analysis. They found distinct metabolite patterns between non-transformed and transformed plants. For example, levels of trehalose 6-phosphate, GABA, and proline were generally higher, while levels of glucose 6-phosphate and UDP-glucose were lower in the fruits of the SlLIP1 transformants.
Moreover, since overexpression of SlLIP1 resulted in lower transcript levels of E2 PDH and E2 kGDH and increased amounts of LA-bound targets, the researchers speculate that the proportion of unlipoylated E2 subunits of PDH and kGDH may have decreased. This research could help in developing crops with higher LA content, potentially offering improved health benefits.
Covarrubias, M. P., Uribe, F., Cabedo, P., & Handford, M. (2025). Fruit-specific overexpression of lipoyl synthase increases both bound and unbound lipoic acid and alters the metabolome of tomato fruits. Frontiers in Plant Science, 16, 1545011. https://doi.org/10.3389/fpls.2025.1545011
Source: Frontiers In