Mechanical stress-induced anthocyanin regulatory genes involved in anthocyanin accumulation in tomato plants

Plants have developed adaptive mechanisms to withstand mechanical stress, which can hinder their growth and productivity. Anthocyanins, water-soluble pigments found in plants, have been shown to confer tolerance to abiotic stresses in various plant species, including tomato plants (Solanum lycopersicum L.). Although the biosynthesis and regulatory factors of anthocyanins have been well-characterized in tomato plants, it remains unclear whether mechanical stress influences the expression of these genes. The aim of this study was to examine the effects of rubbing-induced mechanical stress on the activation of genes involved in anthocyanin regulation and subsequent anthocyanin accumulation in tomato plants. Our results showed that rubbing treatment triggered morphological changes such as reduced plant height and altered stem and leaf color because of anthocyanin accumulation in different tomato varieties. Transcriptional analysis revealed significant upregulation of anthocyanin regulatory and biosynthetic genes in the rubbed stems when compared with the control stems. Furthermore, a negative regulator of anthocyanin, SlMYBL2, was down-regulated in the rubbed stems. However, no significant differences in the expression of anthocyanin-related genes were observed in leaves obtained from the rubbed stems, without directly rubbing the leaves themselves, when compared with the control leaves. These findings indicate that rubbing treatment specifically and immediately activated the expression of anthocyanin-related genes in the areas subjected to mechanical stress. Moreover, we suggest that specific regulatory factors influence anthocyanin accumulation throughout the plant, even in areas not directly exposed to mechanical stress.