The effect of exogenous melatonin on the expression profile of SNAT1 and SNAT2 genes during germination of tomato Solanum lycopersicum L. seeds

Relevance. Seed germination is a critical stage of plant development, regulated by a complex network of hormonal signals. Melatonin (N-acetyl-5-methoxytryptamine) is a highly important secondary metabolite in plant that acts as an antioxidant and phytohormone, and therefore is involved in both physiological processes and stress defense responses. The key enzymes in melatonin biosynthesis are serotonin Nacetyltransferases (SNATs). Despite the previously demonstrated effectiveness of exogenous melatonin in stimulating germination, the feedback mechanisms regulating its endogenous biosynthesis, particu­larly the expression of SNAT genes in tomato (Solanum lycopersicum L.), remain poorly understood.

Materials and Methodology. This study was aimed to analyze the effects of exogenous melatonin differ­ent concentrations on S. lycopersicum seed germination and the SlSNAT1 and SlSNAT2 gene expres­sion. The germination dynamics of control seeds and those treated with melatonin solutions (4 pM and 100 pM), as well as the expression profiles of SlSNATI and SlSNAT2 (using real-time PCR) were assessed.

Results. Melatonin was shown to stimulate seed germination. The most significant difference in the num­ber of seeds germinated per day was observed on the second and third days after treatment. The SlSNAT1 and SlSNAT2 expression levels were found to be different in both control and melatonin-treated samples. On the first and second days of control seedling development, SlSNAT2 was expressed high­er than SlSNAT1, and on the tenth day, vice versa. Treatment with different concentrations of melatonin affected the expression profile of SlSNAT genes differently: when exposed to 4 pM melatonin, a gradual increase in the expression of both genes was observed within 10 days, while for the 100 pM variant, cycli­cality (rise-fall-rise) was shown in the case of SlSNAT1, and an increase (day 2) followed by a slight decrease (days 3, 10) was shown in the case of SlSNAT2. The data obtained expand our understanding of the exogenous melatonin effects on seed germination and the expression pattern of melatonin biosyn­thesis key genes in tomato.

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