Ectopic Expression of an FT Homolog from Citrus Confers an Early Flowering Phenotype on Trifoliate Orange (Poncirus trifoliata L. Raf.)
Citrus FT (CiFT) cDNA, which promoted the transition from the vegetative to the reproductive phase in Arabidopsis thaliana, when constitutively expressed was introduced into trifoliate orange (Poncirus trifoliata L. Raf.). The transgenic plants in which CiFT was expressed constitutively showed early flowering, fruiting, and characteristic morphological changes. They started to flower as early as 12 weeks after transfer to a greenhouse, whereas wild-type plants usually have a long juvenile period of several years. Most of the transgenic flowers developed on leafy inflorescences, apparently in place of thorns; however, wild-type adult trifoliate orange usually develops solitary flowers in the axils of leaves. All of the transgenic lines accumulated CiFT mRNA in their shoots, but there were variations in the accumulation level. The transgenic lines showed variation in phenotypes, such as time to first flowering and tree shape. In F1 progeny obtained by crossing ‘Kiyomi’ tangor (C. unshiu × sinensis) with the pollen of one transgenic line, extremely early flowering immediately after germination was observed. The transgene segregated in F1 progeny in a Mendelian fashion, with complete co-segregation of the transgene and the early flowering phenotype. These results showed that constitutive expression of CiFT can reduce the generation time in trifoliate orange.
KeywordsCitrus early flowering FT trifoliate orange
Araki, T 2001Transition from vegetative to reproductive phaseCurr Opin Plant Biol46368CrossRefPubMedGoogle Scholar Banfield, MJ, Brady, RL 2000The structure of Antirrhinum centroradialis protein (CEN) suggests a role as a kinase regulatorJ Mol Biol29711591170CrossRefPubMedGoogle Scholar Cerdán, PD, Chory, J 2003Regulation of flowering time by light qualityNature423881885CrossRefPubMedGoogle Scholar Halliday, KJ, Salter, MG, Thingnaes, E, Whitelam, GC 2003Phytochrome control of flowering is temperature sensitive and correlates with expression of the floral integrator FTPlant J33875885CrossRefPubMedGoogle Scholar Hayama, R, Yokoi, S, Tamaki, S, Yano, M, Shimamoto, K 2003Adaptation of photoperiodic control pathways produces short-day flowering in riceNature422719722CrossRefPubMedGoogle Scholar Hisada, S, Akihama, T, Endo, T, Moriguchi, T, Omura, M 1997Expressed sequence tags of Citrus fruit during rapid cell development phaseJ Am Soc Hortic Sci122808812Google Scholar Ikoma, Y, Yano, M, Ogawa, K, Yoshioka, T, Xu, ZC, Hisada, S, Omura, M, Moriguchi, T 1996Isolation and evaluation of RNA from polysaccharide-rich tissues in fruit for quality by cDNA library construction and RT-PCRJ Jpn Soc Hortic Sci64809814Google Scholar Izawa, T, Oikawa, T, Sugiyama, N, Tanisaka, T, Yano, M, Shimamoto, K 2002Phytochrome mediates the external light signal to repress FT orthologs in photoperiodic flowering of riceGenes Dev1620062020CrossRefPubMedGoogle Scholar Kaneyoshi (Hiramatsu), J, Kobayashi, S, Nakamura, Y, Shigemoto, N, Doi, Y 1994A simple and efficient gene transfer system of trifoliate orange (Poncirus trifoliata Raf.)Plant Cell Rep13541545CrossRefGoogle Scholar Kardailsky, I, Shukla, VK, Ahn, JH, Dagenais, N, Christensen, SK, Nguyen, JT, Chory, J, Harrison, MJ, Weigel, D 1999Activation tagging of the floral inducer FTScience28619621965CrossRefPubMedGoogle Scholar Kobayashi, Y, Kaya, H, Goto, K, Iwabuchi, M, Araki, T 1999A pair of related genes with antagonistic roles in mediating flowering signalsScience28619601962CrossRefPubMedGoogle Scholar Kojima, S, Takahashi, Y, Kobayashi, Y, Monna, L, Sasaki, T, Araki, T, Yano, M 2002Hd3a, a rice ortholog of the Arabidopsis FT gene, promotes transition to flowering downstream of Hd1 under short-day conditionsPlant Cell Physiol4310961105CrossRefPubMedGoogle Scholar Martín-Trillo, M, Martínez-Zapater, JM 2002Growing up fast: Manipulating the generation time of treesCurr Opin Biotechnol13151155CrossRefPubMedGoogle Scholar Mouradov, A, Glassick, T, Hamdorf, B, Murphy, L, Fowler, B, Marla, S, Teasdale, RD 1998NEEDLY, a Pinus radiata ortholog of FLORICAULA/LEAFY genes, expressed in both reproductive and vegetative meristemsProc Natl Acad Sci USA9565376542CrossRefPubMedGoogle Scholar Murashige, T, Skoog, F 1962A revised medium for rapid growth and bioassays with tobacco tissue culturesPhysiol Plant15473497Google Scholar Nilsson, O, Weigel, D 1997Modulating the timing of floweringCurr Opin Biotechnol8195199CrossRefPubMedGoogle Scholar Peña, L, Martín-Trillo, M, Juárez, J, Pina, JA, Navarro, L, Martínez-Zapater, JM 2001Constitutive expression of Arabidopsis LEAFY or APETALA1 genes in citrus reduces their generation timeNat Biotechnol19263267CrossRefPubMedGoogle Scholar Pillitteri, LJ, Lovatt, CJ, Walling, LL 2004Isolation and characterization of a TERMINAL FLOWER homolog and its correlation with juvenility in citrusPlant Physiol13515401551CrossRefPubMedGoogle Scholar Rottman, WH, Meilan, R, Sheppard, LA, Brunner, AM, Skinner, JS, Ma, C, Cheng, S, Jouanin, L, Pilate, G, Strauss, SH 2000Diverse effects of overexpression of LEAFY and PTLF, a poplar (Populus) homolog of LEAFY/FLORICAULA, in transgenic poplar and ArabidopsisPlant J22235245CrossRefPubMedGoogle Scholar Samach, A, Onouchi, H, Gold, SE, Ditta, GS, Schwartz-Sommer, Z, Yanofsky, MF, Coupland, G 2000Distinct roles of CONSTANS target genes in reproductive development of ArabidopsisScience28816131616CrossRefPubMedGoogle Scholar Simpson, GG, Dean, C 2002Arabidopsis, the Rosetta stone of flowering time?Science296285289CrossRefPubMedGoogle Scholar Spiegel-Roy, P, Goldschmidt, EE 1996Biology of CitrusCambridge University PressNew YorkGoogle Scholar Suárez-López, P, Wheatley, K, Robson, F, Onouchi, H, Valverde, F, Coupland, G 2001CONSTANS mediates between the circadian clock and the control of flowering in ArabidopsisNature41011161120CrossRefPubMedGoogle Scholar Weigel, D, Nilsson, O 1995A developmental switch sufficient for flower initiation in diverse plantsNature377495500CrossRefPubMedGoogle Scholar Yanovsky, MJ, Kay, SA 2002Molecular basis of seasonal time measurement in ArabidopsisNature419308312CrossRefPubMedGoogle Scholar Yamada, Y, Ito, Y, Ueno, I, Yoshida, T 1991Precocious flowering in citrus and kumquat seedlingsBull Fruit Tree Res Stn201323Google Scholar