Expression of gene encoded homogentisate geranylgeranyl transferase involved in tocotrienol biosynthesis in Indonesian local rice (Oryza sativa Linnaeus)

Banyuwangi has various kinds of local rice varieties, including Hitam Melik, Merah Harum, and Genjah Harum. These rice predicted to contain an antioxidant, such as vitamin E or tocochromanol (tocotrienol and tocopherol). Tocotrienol biosynthesis catalyzed by homogentisate geranylgeranyl transferase (HGGT) enzyme. The objective of this study was to determine the expression of gene encoded HGGT. Homogentisate geranylgeranyl transferase (HGGT) gene expression was studied by Quantitative Polymerase Chain Reaction (qPCR) and analyzed using comparative C(T) method or 2^(ΔΔCt) method. HGGT gene expression results in Hitam Melik is higher than in Genjah Harum and Merah Harum. Total tocotrienol contents analyzed using High Performance Liquid Chromatography (HPLC) methods. There are three types of tocotrienol isoforms: α-tocotrienol; γ-tocotrienol; and δ-tocotrienol. Each of the rice varieties showed the different value of tocotrienol, specifically: Hitam Melik (823.54 µg · mL⁻¹); Genjah Harum (692.28 µg · mL⁻¹); and Merah Harum (586.84 µg · mL⁻¹). Total tocotrienol measured by HPLC is in accordance with the gene expression results.