In this study, we investigated the effect of night blue lighting on anthocyanin content and expression of its transcription factors and structural genes in purple paprika fruits. Purple paprika fruits (Capsicum annuum L. ‘Tequila’) were used for this experiment. Before light treatment, we used fifty plants grown under hydroponic conditions (EC 2.5, pH 6.0) in a greenhouse. At 10 days after pollination, we started irradiating the fruits at night with blue LEDs light at wavelength 460 nm and radiation intensity at 500 W-m-2. Control is non-irradiated treatment. Fruits were harvested at 15, 20, and 40 days after pollination, for fresh weight evaluation, then following analysis was performed. In the pigment analysis, anthocyanin content was determined based on cyanidin-3-glucoside. By adding 10% acetic acid to frozen ground fruit sample overnight at 4C, the absorbance was measured at 530 nm. In the gene analysis, RNA was extracted from fruit and cDNA was transcripted using kit with gDNA eraser. Then, cDNA template was mixed with PCR Master Mix for quantitative RT PCR analysis. The result was calculated as relative expression to UBI. As the results, fresh weight was not affected by light. Anthocyanin content of treated fruit increased approximately twice as much as that of control fruits at 15, 20, and 40 days after pollination. Furthermore, the expression levels of transcription factors; HY5, MYB, bHLH, and WDR, and structural genes; PAL, CHS, F3H, ANS, DFR, and UFGT increased in treated fruits. These results indicate that blue light irradiation enhanced anthocyanin synthesis in purple paprika fruits, by increasing the expression of its transcription factors and structural genes.
