Martínez Fuentes, Amparo
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Martínez Fuentes
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- PublicationGibberellin reactivates and maintains ovary-wall cell division causing fruit set in parthenocarpic Citrus species(Elsevier, 2016) Mesejo Conejos, Carlos; Yuste Gallasch, Roberto; Reig Valor, Carmina; Martínez Fuentes, Amparo; Iglesias, Domingo; Muñoz Fambuena, Natalia; Bermejo del Castillo, Almudena; Germanà, Maria Antonietta; Primo Millo, Eduardo; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural[EN] Citrus is a wide genus in which most of the cultivated species and cultivars are natural parthenocarpic mutants or hybrids (i.e. orange, mandarin, tangerine, grapefruit). The autonomous increase in GA(1) ovary concentration during anthesis was suggested as being the stimulus responsible for parthenocarpy in Citrus regardless of the species. To determine the exact GA-role in parthenocarpic fruit set, the following hypothesis was tested: GA triggers and maintains cell division in ovary walls causing fruit set. Obligate and facultative parthenocarpic Citrus species were used as a model system because obligate parthenocarpic Citrus sp (i.e. Citrus unshiu) have higher GA levels and better natural parthenocarpic fruit set compared to other facultative parthenocarpic Citrus (i.e. Citrus clementina). The autonomous activation of GA synthesis in C. unshiu ovary preceded cell division and CYCA1.1 up regulation (a G2-stage cell cycle regulator) at anthesis setting a high proportion of fruits, whereas C. clementina lacked this GA-biosynthesis and CYCA1.1 up-regulation failing in fruit set. In situ hybridization experiments revealed a tissue-specific expression of GA20ox2 only in the dividing tissues of the pericarp. Furthermore, CYCA1.1 expression correlated endogenous GA(1) content with GA(3) treatment, which stimulated cell division and ovary growth, mostly in C clementina. Instead, paclobutrazol (GA biosynthesis inhibitor) negated cell division and reduced fruit set. Results suggest that in parthenocarpic citrus the specific GA synthesis in the ovary walls at anthesis triggers cell division and, thus, the necessary ovary growth rate to set fruit. (C) 2016 Elsevier Ireland Ltd. All rights reserved.
- PublicationThe flower to fruit transition in Citrus is partially sustained by autonomous carbohydrate synthesis in the ovary(Elsevier, 2019-08) Mesejo Conejos, Carlos; Martínez Fuentes, Amparo; Reig Valor, Carmina; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural[EN] Why evergreen fruit tree species accumulate starch in the ovary during flower bud differentiation in spring, as deciduous species do during flower bud dormancy, is not fully understood. This is because in evergreen species carbon supply is assured by leaves during flower development. We suggest the existence of an autonomous mechanism in the flowers which counteracts the competition for photoassimilates with new leaves, until they become source organs. Our hypothesis is that starch accumulated during Citrus ovary ontogeny originates from 1) its own photosynthetic capacity and 2) the mobilization of reserves. Through defoliation experiments, we found that ovaries accumulate starch during flower ontogeny using a dual mechanism: 1) the autotrophic route of source organs activating Rubisco (RbcS) genes expression, and 2) the heterotrophic route of sink organs that hydrolyze sucrose in the cytosol. Defoliation 40 days before anthesis did not significantly reduce ovary growth, flower abscission or starch concentration up to 20 days after anthesis (i.e. 60 days later). Control flowers activated the energy depletion signaling system (i.e. SnRK1) and RbcS gene expression around athesis. Defoliation accelerated and boosted both activities, increasing SPS gene expression (sucrose synthesis), and SUS1, SUS3 and cwINV (sucrose hydrolysis) to maintain a glucose threshold which satisfied its need to avoid abscission.
- PublicationMechanical pruning attenuates alternate bearing in 'Nadorcott' mandarin(Elsevier, 2020-02-05) Mesejo Conejos, Carlos; Martínez Fuentes, Amparo; Reig Valor, Carmina; Balasch Parisi, Sebastià; Primo-Millo, Eduardo; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Dpto. de Estadística e Investigación Operativa Aplicadas y Calidad; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural; Centro de Investigación en Acuicultura y Medio Ambiente; Ministerio de Economía y Competitividad[EN] In Citrus, certain species and/or cultivars are prone to alternate bearing, i.e., a year of heavy crop (ON year) is followed by one of low flowering and light crop (OFF year), and vice-versa. To counteract the fruit effect, we propose a guided mechanical pruning initiated in the spring of an ON year and carried out annually. Our hypothesis is that this gives rise to abundant shoots with well-developed leaves that reach the floral bud inductive period ready to receive the inductive signal and, thus, to induce the bud to bloom the following spring. The experiment was carried out during four consecutive years (2013¿16) using a commercial plantation of `Nadorcott¿ mandarin in southwest Spain. Trees were mechanically pruned: hedging (H) or topping by completely removing the upper shoots of the canopy (T) or by cutting ¿ of their length (T¿). Unpruned trees were used as controls. The experiment began in the spring of an ON-year. T and T¿ carried out in the spring restart the meristem and give rise new shoots that develop in summer and autumn. At the inductive period, the leaves on these new shoots showed a CiFT2 gene expression 4- and 3.7-fold higher than their respective old leaves. In the case of the T¿ their buds avoided the inhibitory effect of the fruit and bloomed the following spring even with the fruit in the cut-back shoot. For the two periods of ON-OFF years of our experiment, cumulative yield of the T treated trees barely increased, whereas T¿ significantly increased with respect to the unpruned trees. We conclude that cutting flowering shoots annually in half-length by means of mechanical pruning (T¿), attenuates alternate bearing behaviour in 'Nadorcott' mandarin. In this experiment, cumulative yield increased by 25% with regard to unpruned trees during the four years of the trial.
- PublicationRinging branches reduces fruitlet abscission by promoting PIN1 expression in `Orri' mandarin(Elsevier, 2022-12-15) Mesejo Conejos, Carlos; Martínez Fuentes, Amparo; Reig Valor, Carmina; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural; Universitat Politècnica de València[EN] Ringing branches is a technique which is widely used to increase the yield of Citrus cultivars with low parthenocarpic ability. When performed during the physiological fruitlet abscission stage it prevents fruitlet drop and increases the number of fruits harvested. This effect has been related with an increased carbohydrate supply, which requires an enhanced photosynthesis efficiency of leafy flowering shoots. Since ringing also reduces vegetative growth, both the number of shoots and the leaves per shoot, the mechanism by which the carbohydrate supply is increased should be revised. Our results show that ringing carried out at this stage maintains the ability of the ovary for cell division mediated by the availability of carbohydrates, as indicated by an increased CcCYCA1.1 expression. But this effect is not linked with an increase in GA(1) biosynthesis (CcGA3ox1 expression), as this occurs during fruit set; hence, hormones other than gibberellin must be controlling the physiological fruitlet abscission in response to ringing. We found that an increased expression of the auxin efflux carrier CcPIN1 gene suggests that ringing induces the auxin export out of the fruitlet and transport to the abscission zone (AZ-C), thus inhibiting its activation and allowing carbohydrates supply to the fruitlet which, thus, prevents abscission and continues growth.
- PublicationFruit-dependent epigenetic regulation of flowering in Citrus(Blackwell Publishing, 2020-01) Agustí Fonfría, Manuel; Mesejo Conejos, Carlos; Muñoz-Fambuena, Natalia; Vera Sirera, Francisco José; de Lucas, Miguel; Martínez Fuentes, Amparo; Reig Valor, Carmina; Iglesias, Domingo J.; Primo-Millo, Eduardo; Blazquez Rodriguez, Miguel Angel; Dpto. de Producción Vegetal; Instituto Universitario Mixto de Biología Molecular y Celular de Plantas; Dpto. de Biotecnología; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural; Ministerio de Economía y Competitividad; Università degli Studi di Palermo; Ministerio de Ciencia e Innovación[EN] In many perennial plants, seasonal flowering is primarily controlled by environmental conditions, but in certain polycarpic plants, environmental signals are locally gated by the presence of developing fruits initiated in the previous season through an unknown mechanism. Polycarpy is defined as the ability of plants to undergo several rounds of reproduction during their lifetime, alternating vegetative and reproductive meristems in the same individual. To understand how fruits regulate flowering in polycarpic plants, we focused on alternate bearing in Citrus trees that had been experimentally established as fully flowering or nonflowering. We found that the presence of the fruit causes epigenetic changes correlating with the induction of the CcMADS19 floral repressor, which prevents the activation of the floral promoter CiFT2 even in the presence of the floral inductive signals. By contrast, newly emerging shoots display an opposite epigenetic scenario associated with CcMADS19 repression, thereby allowing the activation of CiFT2 the following cold season.
- PublicationTree water status influences fruit splitting in Citrus(Elsevier, 2016) Mesejo Conejos, Carlos; Reig Valor, Carmina; Martínez Fuentes, Amparo; GAMBETTA, GIULIANA; Gravina Telechea, Alfredo; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural[EN] Fruit splitting or cracking is a major physiological disorder in fruit trees markedly influenced by environmental conditions, but conclusive data still are required to provide a definite explanation and preventive measures. Changes in climatic conditions critically influence fruit splitting incidence. We studied plant-soil-ambient water relations in splitting-prone citrus grown under 4 contrasting environmental conditions (climate type and soil), in Spain and Uruguay, over a six years period. Automatic trunk and fruit diameter measurements (trunk and fruit growth rate and maximum daily trunk shrinkage), which are a tree water status indicator, together with factors modifying the tree and fruit water relationship (temperature, ET, rainfall, soil texture, soil moisture, rootstock and xylem anatomy) were studied and correlated with splitting. A close fruit splitting and soil texture relationship was found, inversely correlated with clay and silt percentages, and positively with those for sand. Under 85%-sand soil conditions, slight changes in soil moisture due to fluctuations in temperature, ET, or rainfall changed trunk and fruit growth rate patterns during few hours and induced splitting. Splitting incidence was higher in trees with larger xylem vessels in the fruit peduncle due to rootstock ('Carrizo' and 'C-35' citrange being higher than 'FA-5', 'Cleopatra' and Poncirus trifoliata). Finally, reducing the frequency of irrigation by half increased midday canopy temperatures (similar to 5 degrees C) and splitting (+15%). We conclude that irregularities in the tree water status, due to interactions among soil moisture, rootstock and climatic conditions, leads to a number of substantial changes in fruit growth rate increasing the incidence of fruit splitting. (C) 2016 Elsevier B.V. All rights reserved.
- PublicationFruit load restricts the flowering promotion effect of paclobutrazol in alternate bearing Citrus spp(Elsevier, 2013-02-28) Martínez Fuentes, Amparo; Mesejo Conejos, Carlos; Muñoz Fambuena, Natalia; Reig Valor, Carmina; Gonzalez Más, Mª Carmen; Iglesias, D. J.; Primo Millo, Eduardo; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural; Ministerio de Ciencia e InnovaciónThe floral bud inductive period, PBZ promotes flowering in Citrus; however, our results indicate that this effect is fruit-load dependant. In 'Salustiana' and 'Navelina' sweet oranges, 'Hernandina' Clementine mandarin, and 'Afourer' and 'Moncada' hybrids, flowering intensity significantly increased the following spring for medium-to-low fruit-load trees treated with either 1-10g PBZ tree(-1) applied to the soil or 15 g tree(-1) sprayed on the canopy. PBZ significantly increased the percentage of sprouted buds and leafless floral shoots (both single-flowered shoots and inflorescences) and reduced the number of vegetative shoots. By contrast, heavy fruit load trees receiving the same amount of PBZ in the same season or at floral bud differentiation period scarcely flowered. Fruit nullified the effect of PBZ irrespective to treatment date (inductive period or bud burst) as well as the dose applied (1, 10 or 15 g tree(-1)) or the treatment method (soil application or canopy spraying). In conclusion, the effectiveness of PBZ in promoting flowering in Citrus depends on the fruit load since the tree showed a cultivar-dependant threshold value above which PBZ is unable to promote flowering. (C) 2012 Elsevier B.V. All rights reserved.
- PublicationGenetic inhibition of flowering differs between juvenile and adult Citrus trees(Oxford University Press, 2019-02-15) Muñoz Fambuena, Natalia; Nicolas-Almansa, M.; Martínez Fuentes, Amparo; Reig Valor, Carmina; Iglesias, D. J.; Primo-Millo, Eduardo; Mesejo Conejos, Carlos; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural; Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria[EN] Background and Aims In woody species, the juvenile period maintains the axillary meristems in a vegetative stage, unable to flower, for several years. However, in adult trees, some 1-year-old meristems flower whereas others remain vegetative to ensure a polycarpic growth habit. Both types of trees, therefore, have non-flowering meristems, and we hypothesize that the molecular mechanism regulating flower inhibition in juvenile trees is different from that in adult trees. Methods In adult Citrus trees, the main endogenous factor inhibiting flower induction is the growing fruit. Thus, we studied the expression of the main flowering time, identity and patterning genes of trees with heavy fruit load (not-flowering adult trees) compared to that of 6-month-old trees (not-flowering juvenile trees). Adult trees without fruits (flowering trees) were used as a control. Second, we studied the expression of the same genes in the meristems of 6-month, and 1-, 3-, 5-and 7-year-old juvenile trees compared to 10-year-old flowering trees. Key Results The axillary meristems of juvenile trees are unable to transcribe flowering time and patterning genes during the period of induction, although they are able to transcribe the FLOWERING LOCUS T citrus orthologue (CiFT2) in leaves. By contrast, meristems of not-flowering adult trees are able to transcribe the flowering network genes but fail to achieve the transcription threshold required to flower, due to CiFT2 repression by the fruit. Juvenile meristems progressively achieve gene expression, with age-dependent differences from 6 months to 7 years, FD-like and CsLFY being the last genes to be expressed. Conclusions During the juvenile period the mechanism inhibiting flowering is determined in the immature bud, so that it progressively acquires flowering ability at the gene expression level of the flowering time programme, whereas in the adult tree it is determined in the leaf, where repression of CiFT2 gene expression occurs.
- PublicationGibberellic acid and norflurazon affecting the time-course of flavedo pigment and abscisic acid content in Valencia sweet orange(Elsevier, 2014-12-17) Gambetta Romaso, María Giuliana; Mesejo Conejos, Carlos; Martínez Fuentes, Amparo; Reig Valor, Carmina; Gravina Telechea, Alfredo; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio NaturalIn Citrus, colour break has been positively related to ethylene, abscisic acid (ABA) and carbohydrates, and negatively related to gibberellins and nitrogen. However, the mechanisms by which these substances affect the process are not well understood. This study analyses the role of gibberellins and ABA, through gibberellic acid (GA(3)) and norflurazon (NFZ) applications, on the evolution of flavedo pigments in on-tree degreening and regreening 'Valencia' sweet orange fruit. In two experiments, 180 fruits were tagged previous to colour break, 60 were treated with NFZ, another 60 with GA(3), and the remaining 60 were used as control. In control fruit, flayed ABA concentration increased as did colour development, declining just before full colour developed. NFZ did not affect chlorophyll degradation, but provoked a partial blockage of the carotenoid biosynthesis pathway increasing phytoene and phytofluene concentrations in the flavedo. As a consequence, flavedo ABA concentration temporarily reduced as did fruit colour intensity, but it did not delay the onset of colour break. Conversely, GA(3) delayed flavedo chlorophyll degradation and reduced beta-cryptoxanthin and beta-citraurin biosynthesis, and, thus, delayed fruit colour break. GA(3)-treated fruit also accumulated higher lutein and beta-carotene concentrations, but remained greener than control fruit, and reduced flavedo ABA concentration, but not significantly. Ethylene was not detected, in any treatment. Our results confirm that ABA concentration paralleled colour development, but it did not trigger the process. (C) 2014 Elsevier B.V. All rights reserved.
- PublicationSoil-to-fruit nitrogen flux mediates the onset of fruit-nitrogen remobilization and color change in citrus(Elsevier, 2022-12) Mesejo Conejos, Carlos; Lozano-Omeñaca, Aurora; Martínez Fuentes, Amparo; Reig Valor, Carmina; Gambetta, G.; Marzal, A.; Martínez-Alcántara, B.; Gravina, A.; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural; Universitat Politècnica de València[EN] In non-climacteric fruit tree species, color change is primarily controlled by the interplay between environmental conditions, nutritional factors (nitrogen and sugars) and hormones, mainly abscisic acid and gibberellins (GA), through a complex mechanism which is not completely understood. Nitrogen has a strong impact on color change, influenced by environmental changes, either locally or at the whole tree level. We use Citrus trees, as a non-climacteric model species, to understand the long-distance nitrogen signaling mechanism delaying the chloroplast-to-chromoplast transition at the molecular level. It is unknown whether nitrogen regulates the branch point of geranylgeranyl diphosphate (GGPP), the shared precursor for gibberellin, chlorophyll and carotenoid synthesis. We used 15N to trace the root-to-fruit nitrogen flux in trees grown under soils differing in nitrogen content and temperature, and treated with NH4NO3 and GA. Key genes involved in nitrogen signaling, transport and metabolism, and those from the GGPP branch point were analyzed in the fruit. Results explain how soil temperature modifies 15N transport to play a key role in signaling citrus color change, and show that fruit -nitrogen remobilization is required for triggering degreening. Nitrogen content in the fruit modulates the onset of glutamate deamination, asparagine synthesis, nitrite assimilation and GA1 depletion. Expression of the nitrate transporter NRT1.2, glutamate dehydrogenase and asparagine synthetase genes was high right before the start of degreening, together with NH4+ concentration. Nitrogen delayed carotenoid synthesis (phytoene synthase gene expression) without modifying gibberellin synthesis (ent-kaurene synthase and oxidase) at the chloroplast level.