title: Provitamin A accumulation in cassava (Manihot esculenta) roots driven by a single nucleotide polymorphism in a phytoene synthase gene.
abstract: Cassava (Manihot esculenta) is an important staple crop, especially in the arid tropics. Because roots of commercial cassava cultivars contain a limited amount of provitamin A carotenoids, both conventional breeding and genetic modification are being applied to increase their production and accumulation to fight vitamin A deficiency disorders. We show here that an allelic polymorphism in one of the two expressed phytoene synthase (PSY) genes is capable of enhancing the flux of carbon through carotenogenesis, thus leading to the accumulation of colored provitamin A carotenoids in storage roots. A single nucleotide polymorphism present only in yellow-rooted cultivars cosegregates with colored roots in a breeding pedigree. The resulting amino acid exchange in a highly conserved region of PSY provides increased catalytic activity in vitro and is able to increase carotenoid production in recombinant yeast and Escherichia coli cells. Consequently, cassava plants overexpressing a PSY transgene produce yellow-fleshed, high-carotenoid roots. This newly characterized PSY allele provides means to improve cassava provitamin A content in cassava roots through both breeding and genetic modification.
authors.affiliation: University of Freiburg, Faculty of Biology, Freiburg, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Welsch
authors.forename: Jacobo
authors.initials: J
authors.lastname: Arango
authors.forename: Cornelia
authors.initials: C
authors.lastname: Bär
authors.forename: Bertha
authors.initials: B
authors.lastname: Salazar
authors.forename: Salim
authors.initials: S
authors.lastname: Al-Babili
authors.forename: Jesús
authors.initials: J
authors.lastname: Beltrán
authors.forename: Paul
authors.initials: P
authors.lastname: Chavarriaga
authors.forename: Hernan
authors.initials: H
authors.lastname: Ceballos
authors.forename: Joe
authors.initials: J
authors.lastname: Tohme
authors.forename: Peter
authors.initials: P
authors.lastname: Beyer
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism*; D000483:Alleles; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase; D002365:Manihot / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D010858:Pigmentation; D018517:Plant Roots / Q000201:enzymology* / Q000235:genetics; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D016415:Sequence Alignment; D014801:Vitamin A / Q000096:biosynthesis*
chemical_list: D018744:DNA, Plant; D014801:Vitamin A; D019883:Alkyl and Aryl Transferases; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase