title: Identification and characterization of an Arabidopsis homogentisate phytyltransferase paralog.
abstract: Tocochromanols (tocopherols and tocotrienols) are micronutrients with antioxidant properties synthesized by photosynthetic bacteria and plants that play important roles in animal and human nutrition. There is considerable interest in identifying the genes involved in tocochromanol biosynthesis to allow transgenic modification of both tocochromanol levels and tocochromanol composition in agricultural crops. The first committed reaction in tocopherol biosynthesis is the condensation of homogentisic acid (HGA) with phytyldiphosphate or geranylgeranyldiphosphate, catalyzed by the homogentisate phytyltransferase (VTE2) or by the homogentisate geranylgeranyl transferase (HGGT). In this study, we describe the identification of conserved amino acid sequences within VTE2 and HGGT and the application of these conserved sequences for a motif analysis resulting in the discovery of a VTE2-paralog in the Arabidopsis genome. We designated this new gene VTE2-2 and renamed the old VTE2 to VTE2-1. Seed-specific expression of VTE2-2 in Arabidopsis resulted in increased seed-tocopherol levels, similar to the transgenic expression of VTE2-1. Bioinformatics analysis revealed that VTE2-2 is conserved in both monocotyledonous and dicotyledonous plants and is distinct from VTE2-1 and HGGT.
authors.affiliation: Monsanto Company, 800 N. Lindbergh Boulevard, St. Louis, MO 63167, USA.
authors.forename: Tyamagondlu V
authors.initials: TV
authors.lastname: Venkatesh
authors.forename: Balasulojini
authors.initials: B
authors.lastname: Karunanandaa
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Free
authors.forename: Jeannie M
authors.initials: JM
authors.lastname: Rottnek
authors.forename: Susan R
authors.initials: SR
authors.lastname: Baszis
authors.forename: Henry E
authors.initials: HE
authors.lastname: Valentin
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D016375:Antisense Elements (Genetics); D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D019295:Computational Biology; D017124:Conserved Sequence; D008969:Molecular Sequence Data; D010802:Phylogeny; D030821:Plants, Genetically Modified / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D024505:Tocopherols / Q000378:metabolism*
chemical_list: D016375:Antisense Elements (Genetics); D029681:Arabidopsis Proteins; D019883:Alkyl and Aryl Transferases; C446531:HPT1 protein, Arabidopsis; D024505:Tocopherols