title: FLOWERING LOCUS T genes control onion bulb formation and flowering.
abstract: Onion (Allium cepa L.) is a biennial crop that in temperate regions is planted in the spring and, after a juvenile stage, forms a bulb in response to the lengthening photoperiod of late spring/summer. The bulb then overwinters and in the next season it flowers and sets seed. FLOWERING LOCUS T (FT) encodes a mobile signaling protein involved in regulating flowering, as well as other aspects of plant development. Here we show that in onions, different FT genes regulate flowering and bulb formation. Flowering is promoted by vernalization and correlates with the upregulation of AcFT2, whereas bulb formation is regulated by two antagonistic FT-like genes. AcFT1 promotes bulb formation, while AcFT4 prevents AcFT1 upregulation and inhibits bulbing in transgenic onions. Long-day photoperiods lead to the downregulation of AcFT4 and the upregulation of AcFT1, and this promotes bulbing. The observation that FT proteins can repress and promote different developmental transitions highlights the evolutionary versatility of FT.
authors.affiliation: Department of Biochemistry, University of Otago, 9016 Dunedin, PO Box 56 Dunedin, New Zealand.
authors.forename: Robyn
authors.initials: R
authors.lastname: Lee
authors.forename: Samantha
authors.initials: S
authors.lastname: Baldwin
authors.forename: Fernand
authors.initials: F
authors.lastname: Kenel
authors.forename: John
authors.initials: J
authors.lastname: McCallum
authors.forename: Richard
authors.initials: R
authors.lastname: Macknight
mesh_terms: D000595:Amino Acid Sequence; D035264:Flowers / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D019697:Onions / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010944:Plants / Q000737:chemistry / Q000145:classification / Q000235:genetics; D012621:Seasons; D016415:Sequence Alignment; D013696:Temperature
chemical_list: D010940:Plant Proteins