Genetic Diversity within the Vitamin E Biosynthetic Pathway of Sunflower

Sunflower (Helianthus annuus) is one of the world’s most important oil seed crops. It’s oil’s oxidative stability and shelf life is conferred, amongst other, by it’s vitamin E (tocopherol) content. The biosynthetic pathway of tocopherol however, has yet to be fully characterized in sunflower. This research aims to: (1) identify the tocopherol biosynthetic gene homologs in public bioinformatic databases in order to construct a biosynthetic pathway and (2) to identify and characterize the genetic diversity of tocopherol genes using next generation DNA sequencing technologies. The identified candidate genes were assigned to Gene Ontology (GO) terms, mapped in TAIR and remapped in KEGG Orthology (KO) database. The resultant reference pathway, “Ubiquinone and other Terpenoid Quinone biosynthesis pathway” was further analyzed and the tocopherol pathway was constructed. This pathway was used to select the genes TC, TMT, HPT and HPPD responsible for the production of tocopherol derivatives. The four specific gene sequences were retrieved from NCBI and aligned to the Helianthus annuus draft genome to determine consensus sequences for each gene. Sequencing revealed that 74,5M reads mapped for the gene TC and 64,3M for TMT to Helianthus annuus on NCBI with a 100% and 96% nucleotide similarity, respectively. The gene sequences HPPD (1900) and HPT (4,7M) mapped against Lactuva sativa, a close relative of sunflower. The gene HPPD showed 80% nucleotide similarity while HPT had 91% similarity. These genes will be further analyzed for 104 sunflower accessions to develop SNP markers for oxidative stability and shelf life for future breeding.