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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    • "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.
    Journal of Plant Physiology 01/2015; 177C:11-19. DOI:10.1016/j.jplph.2015.01.003 · 2.56 Impact Factor
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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.
    Frontiers in Plant Science 09/2014; 5:465. DOI:10.3389/fpls.2014.00465 · 3.95 Impact Factor
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    • "In plants, members of the family have been shown to be involved in the transition of vegetative to reproductive stage, in architecture elaboration or in the control of the growth and termination of meristems (Bradley et al., 1996; Kardailsky et al., 1999; Lifschitz & Eshed, 2006; Shalit et al., 2009). In Arabidopsis, in addition to FT, the CETS gene family includes five other closely related genes: TERMINAL FLOWER 1 (TFL1, a repressor of flowering), ARABIDOPSIS THALIANA CENTRORADIALIS (ATC), TWIN SISTER OF FT (TSF), MOTHER OF FT AND TFL1 (MFT) and BROTHER OF FT AND TFL1 (BFT) (Mimida et al., 2001; Yoo et al., 2004, 2010; Yamaguchi et al., 2005). "
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    ABSTRACT: Understanding the genetic basis of the timing of bud set, an important trait in conifers, is relevant for adaptation and forestry practice. In common garden experiments, both Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) show a latitudinal cline in the trait. We compared the regulation of their bud set biology by examining the expression of PsFTL2, a Pinus sylvestris homolog to PaFTL2, a FLOWERING LOCUS T/TERMINAL FLOWER 1 (FT/TFL1)-like gene, the expression levels of which have been found previously to be associated with the timing of bud set in Norway spruce. In a common garden study, we analyzed the relationship of bud phenology under natural and artificial photoperiods and the expression of PsFTL2 in a set of Scots pine populations from different latitudes. The expression of PsFTL2 increased in the needles preceding bud set and decreased during bud burst. In the northernmost population, even short night periods were efficient to trigger this expression, which also increased earlier under all photoperiodic regimes compared with the southern populations. Despite the different biology, with few limitations, the two conifers that diverged 140 million yr ago probably share an association of FTL2 with bud set, pointing to a common mechanism for the timing of growth cessation in conifers.
    New Phytologist 06/2014; 204(1). DOI:10.1111/nph.12901 · 7.67 Impact Factor
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