Journal of agricultural and food chemistry 2017 11 09() doi 10.1021/acs.jafc.7b03448
Tocopherols composed of four isoforms (α, β, γ and δ) and its biosynthesis comprises of three pathways; Methylerythritol 4-phosphate (MEP), shikimate (SK) and tocopherol-core pathways regulated by 25 enzymes. To understand pathway regulatory mechanism at transcriptional level, gene expression profile of tocopherol-biosynthesis genes in two soybean genotypes was carried out, the results showed significantly differential expression of 5 genes; 1-deoxy-D-xylulose-5-P-reductoisomerase (DXR), geranyl geranyl reductase (GGDR)¬ – from MEP; arogenate dehydrogenase (TyrA), tyrosine aminotransferase (TAT) – from SK and γ-tocopherol methyl transferase 3 (γ-TMT3) from tocopherol-core pathways. Expression data were further analyzed for total tocopherol (T-toc) and α-tocopherol (α-toc) content by coregulation network and gene clustering approaches, the results showed least and strong association of γ-TMT3/ tocopherol cyclase (TC) and DXR/DXS respectively with gene clusters of tocopherol biosynthesis suggested the specific role of γ-TMT3/TC in determining tocopherol accumulation and intricacy of DXR/DXS genes in coordinating precursor pathways towards tocopherol biosynthesis in soybean seeds. Thus the present study provides insight into the major role of these genes regulating the tocopherol synthesis in soybean seeds. Key words: VitaminE, tocopherols, MEP, SK, soybean, phytyl 2P, Homogentisate, α-tocopherol.