Universal florigenic triggered by FT homologues regulate growth and flowering cycles in perennial day-neutral tomato

Department of Biology, Technion I.I.T. Haifa, 32000, Israel.
Journal of Experimental Botany (Impact Factor: 5.53). 02/2006; 57(13):3405-14. DOI: 10.1093/jxb/erl106
Source: PubMed


The transition from vegetative to floral meristems in higher plants is programmed by the coincidence of internal and environmental
signals. Classic grafting experiments have shown that leaves, in response to changing photoperiods, emit systemic signals,
dubbed ‘florigen’, which induce flowering at the shoot apex. The florigen paradigm was conceived in photoperiod-sensitive
plants: nevertheless it implies that although activated by different stimuli in different flowering systems, the signal is
common to all plants. Tomato is a day-neutral, perennial plant, with sympodial and modular organization of its shoots and
thus with reiterative regular vegetative/reproductive transitions. SINGLE FLOWER TRUSS a regulator of flowering-time and shoot architecture encodes the tomato orthologue of FT, a major flowering integrator gene in Arabidopsis. SFT generates graft-transmissible signals which complement the morphogenetic defects in sft plants, substitute for light dose stimulus in tomato and for contrasting day-length requirements in Arabidopsis and MARYLAND MAMMOTH tobacco. It is discussed how systemic signals initiated by SFT interact with the SELF PRUNING gene to regulate vegetative to reproductive (V/R) transitions in the context of two flowering systems, one for primary apices
and the other for sympodial shoots.

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    • "The mutation in FD results in late flowering and suppresses the early flowering phenotype of FT overexpression lines, suggesting that FD mediates the function of FT in regulating flowering (Wigge et al., 2005). In addition to the extensive studies in Arabidopsis, FT and FD have also been identified in other plants such as tomato (Pnueli et al., 2001;Lifschitz and Eshed, 2006), pea (Sussmilch et al., 2015), kiwifruit (VarkonyiGasic et al., 2013), rose (Randoux et al., 2014), strawberry (Mouhu et al., 2009), poplar (Bohlenius et al., 2006;Hsu et al., 2006;Tylewicz et al., 2015), Satsuma mandarin (Endo et al., 2005;Nishikawa et al., 2007), and apple (Kotoda et al., 2010;Guitton et al., 2012). Functional characterization of these genes has revealed that they have a conserved role in regulating flowering. "
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    ABSTRACT: In angiosperms, regulation of flowering is a vital process for successful reproduction. To date, the molecular mechanism of flowering is well-studied in the model plant, Arabidopsis, in which key genes such as FLOWERING LOCUST (FT) or FD have been identified to regulate flowering. However, the flowering mechanisms are still largely unknown in fruit trees like loquat. To this end, we first cloned one FT- and two FD-like genes from the loquat (Eriobotrya deflexa Nakai f. koshunensis) and referred to as EdFT, EdFD1, and EdFD2, respectively. Phylogenetic analysis has shown that EdFT, EdFD1, and EdFD2 are conserved during the evolution process. EdFT is mainly expressed in reproductive tissues (e.g., flower buds, flowers, and fruits), while EdFD1 and EdFD2 are mainly expressed in apical buds including leaf buds and flower buds. EdFT is localized in the whole cell, while EdFD1 or EdFD2 is localized in the nucleus. Ectopic expression of EdFT, EdFD1, and EdFD2 in Arabidopsis results in early flowering. In addition, we have also revealed that the EdFT interacts with both EdFD1 and EdFD2. Overall, these data suggest that the EdFT, EdFD1, and EdFD2 are the functional homologs of FT and FD, respectively, which might act together to regulate loquat flowering through a similar mechanism found in Arabidopsis.
    Preview · Article · Jan 2016 · Frontiers in Plant Science
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    • "Determinate tomato plants (sp/sp) heterozygous for the loss-of-function allele of SFT (sft mutation) produce a greater number of leaves, inflorescences, and flowers per inflorescence, which, coupled to a higher individual fruit weight, lead to up to 60% increase in yield, when compared to isogenic sp/sp plants (Krieger et al., 2010; Jiang et al., 2013). If homozygous in a sp/sp background, the sft mutation leads to the production of an indeterminate vegetative inflorescence, resulting in a plant with reduced fruit production (Molinero-Rosales et al., 2004; Lifschitz et al., 2006; Shalit et al., 2009). Determinate growth in sp/sp tomatoes causes almost simultaneous fruit ripening, which, in addition to the compact growth habit, allows large-scale mechanical harvesting (Stevens and Rick, 1986). "
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    ABSTRACT: Tomato (Solanum lycopersicum) shows three growth habits: determinate, indeterminate and semi-determinate. These are controlled mainly by allelic variation in the SELF-PRUNING (SP) gene family, which also includes the "florigen" gene SINGLE FLOWER TRUSS (SFT). Determinate cultivars have synchronized flower and fruit production, which allows mechanical harvesting in the tomato processing industry, whereas indeterminate ones have more vegetative growth with continuous flower and fruit formation, being thus preferred for fresh market tomato production. The semi-determinate growth habit is poorly understood, although there are indications that it combines advantages of determinate and indeterminate growth. Here, we used near-isogenic lines (NILs) in the cultivar Micro-Tom (MT) with different growth habit to characterize semi-determinate growth and to determine its impact on developmental and productivity traits. We show that semi-determinate genotypes are equivalent to determinate ones with extended vegetative growth, which in turn impacts shoot height, number of leaves and either stem diameter or internode length. Semi-determinate plants also tend to increase the highly relevant agronomic parameter Brix×ripe yield (BRY). Water-use efficiency (WUE), evaluated either directly as dry mass produced per amount of water transpired or indirectly through C isotope discrimination, was higher in semi-determinate genotypes. We also provide evidence that the increases in BRY in semi-determinate genotypes are a consequence of an improved balance between vegetative and reproductive growth, a mechanism analogous to the conversion of the overly vegetative tall cereal varieties into well-balanced semi-dwarf ones used in the Green Revolution. Copyright © 2015 Elsevier GmbH. All rights reserved.
    Full-text · Article · Jan 2015 · Journal of Plant Physiology
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    • "The sympodial shoot system of tomato is a conglomerate of three branching habits: (A) Axillary meristems of the primary shoot, which are first arrested by apical cues but are gradually released from dormancy after floral termination of the apical meristems above them (Figure 1). (B) Sympodial branching, involving an axillary meristem, hosted by the third leaf of each SU that is not subjected to apical dominance and grows out in response to signals generated by the terminating SAM, with no intervening dormancy to form the next SU (Lifschitz and Eshed, 2006). When the termination of the sympodial apex is delayed or accelerated, the formation of the next SU will be affected in a similar manner. "
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    ABSTRACT: Genetic studies in Arabidopsis established FLOWERING LOCUS T (FT) as a key flower-promoting gene in photoperiodic systems. Grafting experiments established unequivocal one-to-one relations between SINGLE FLOWER TRUSS (SFT), a tomato homolog of FT, and the hypothetical florigen, in all flowering plants. Additional studies of SFT and SELF PRUNING (SP, homolog of TFL1), two antagonistic genes regulating the architecture of the sympodial shoot system, have suggested that transition to flowering in the day-neutral and perennial tomato is synonymous with "termination." Dosage manipulation of its endogenous and mobile, graft-transmissible levels demonstrated that florigen regulates termination and transition to flowering in an SP-dependent manner and, by the same token, that high florigen levels induce growth arrest and termination in meristems across the tomato shoot system. It was thus proposed that growth balances, and consequently the patterning of the shoot systems in all plants, are mediated by endogenous, meristem-specific dynamic SFT/SP ratios and that shifts to termination by changing SFT/SP ratios are triggered by the imported florigen, the mobile form of SFT. Florigen is a universal plant growth hormone inherently checked by a complementary antagonistic systemic system. Thus, an examination of the endogenous functions of FT-like genes, or of the systemic roles of the mobile florigen in any plant species, that fails to pay careful attention to the balancing antagonistic systems, or to consider its functions in day-neutral or perennial plants, would be incomplete.
    Full-text · Article · Sep 2014 · Frontiers in Plant Science
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