Martínez Fuentes, Amparo
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Martínez Fuentes
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Amparo
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- PublicationHormonal and carbohydrate control of fruit set in avocado 'Lamb Hass'. A question of the type of inflorescence?(Elsevier, 2021-05-10) D'Asaro, Antonio; Reig Valor, Carmina; Martínez Fuentes, Amparo; Mesejo Conejos, Carlos; Farina, Vittorio; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural; Università degli Studi di Palermo[EN] The avocado tree (Persea americana Mill.) has two types of shoots, indeterminate, which maintain vegetative development from an apical bud, and determinate, which do not have vegetative growth. Indeterminate shoots set fewer fruits than determinate ones, and significantly hasten physiological fruitlet abscission. The competition between vegetative and flower development is accepted as the most reasonable hypothesis to explain the differences. However, our results show that from anthesis until fruit set flowers of indeterminate inflorescences, both those remaining on the tree and those abscised, had a higher sucrose and C6 carbohydrate content than flowers of determinate ones and no differences between them were found for C7 carbohydrates, which disagrees with this hypothesis, and indicates that factors other than carbohydrate content are responsible for fruit set in avocado. At anthesis and fruit set stage, gibberellin and cytokinin concentrations (mainly GA1 and tZ, respectively) were significantly higher in flowers of determinate inflorescences than in those of indeterminate ones, indicating their higher ability to set. We conclude that fruit set is hormonally regulated in avocado, irrespective of vegetative growth. The lower fruit set of the indeterminate inflorescences does not depend on the competition for photosynthates due to the apical vegetative growth, since C6 and C7 carbohydrate availability is enough to ensure fruit set, but on their lower content of GA1 and tZ.
- PublicationWarm temperature during floral bud transition turns off EjTFL1 gene expression and promotes flowering in Loquat (Eriobotrya japonica Lindl)(Elsevier, 2023-10) García-Lorca, Ana; Reig Valor, Carmina; Martínez Fuentes, Amparo; Agustí Fonfría, Manuel; Mesejo Conejos, Carlos; Dpto. de Producción Vegetal; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural; Universitat Politècnica de València[EN] The Rosaceae family includes several deciduous woody species whose flower development extends over two consecutive growing seasons with a winter dormant period in between. Loquat (Eriobotrya japonica Lindl.) belongs to this family, but it is an evergreen species whose flower bud initiation and flowering occur within the same growing year. Vegetative growth dominates from spring to late summer when terminal buds bloom as panicles. Thus, its floral buds do not undergo winter dormancy until flowering, but a summer heat period of dormancy is required for floral bud differentiation, and that is why we used loquat to study the mechanism by which this summer rest period contributes to floral differentiation of Rosaceae species. As for the deciduous species, the bud transition to the generative stage is initiated by the floral integrator genes. There is evidence that combinations of environmental signals and internal cues (plant hormones) control the expression of TFL1, but the mechanism by which this gene regulates its expression in loquat needs to be clarified for a better understanding of its floral initiation and seasonal growth cycles. Under high temperatures (>25 & DEG;C) after floral bud inductive period, EjTFL1 expression decreases during meristem transition to the reproductive stage, and the promoters of flowering (EjAP1 and EjLFY) increase, indicating that the floral bud differentiation is affected by high temperatures. Monitoring the apical meristem of loquat in June-August of two consecutive years under ambient and thermal controlled conditions showed that under lower temperatures (<25 & DEG;C) during the same period, shoot apex did not stop growing and a higher EjTFL1 expression was recorded, preventing the bud to flower. Likewise, temperature directly affects ABA content in the meristem paralleling EjTFL1 expression, suggesting signaling cascades could converge to refine the expression of EjTFL1 under specific conditions (T<25 & DEG;C) during the floral transition stage.
- PublicationOn how auxin, ethylene and IDA-peptide relate during mature Citrus fruit abscission(Elsevier, 2021-02-27) Mesejo Conejos, Carlos; Marzal, A.; 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] While the ethylene-auxin interactions are well documented in model dicots such as tomato (climacteric fruit) during mature fruit abscission, the process is not clearly understood in citrus (non-climacteric fruit). The mature fruit produces very little ethylene but is sensitive to ethylene treatments to induce abscission. By contrast, auxin treatments delay fruit abscission, but the particular role of auxin in the process is unknown. Since the IDA-HAE/HSL2 ethylene-independent pathway seem to regulate organ abscission in both model and crop species, we proposed that auxin treatment delays citrus fruit abscission by reactivating the basipetal auxin flux and reducing CitIDA3 expression, without modifying ethylene synthesis. Comparing orange (C. sinensis) genotypes which differ in their abscission rate, 'Navelate' vs. 'Valencia Late', we found that the force needed to detach the fruit from the tree (FDF) declines in parallel with 1) an increase of ethylene synthesis and CitIDA3 gene expression, and 2) a reduction of PIN1-like (auxin transporter) gene expresion. Further, auxin (2,4-D) treatment maintains a higher force in the abscission zone upregulating PIN1-like and AUX1-like (auxin transporter) gene expression, and downregulating CitIDA3 gene expression, but without modifying ethylene production. We conclude that the 2,4-D treatment delays citrus mature fruit abscission through an ethylene-independent pathway.
- 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.
- 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.
- PublicationReversion of fruit-dependent inhibition of flowering in Citrus requires sprouting of buds with epigenetically silenced CcMADS19(Blackwell Publishing, 2022-01) Mesejo Conejos, Carlos; Marzal Blay, Andrés; Martínez Fuentes, Amparo; Reig Valor, Carmina; de Lucas, Miguel; Iglesias, Domingo J.; Primo-Millo, Eduardo; Blazquez Rodriguez, Miguel Angel; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Instituto Universitario Mixto de Biología Molecular y Celular de Plantas; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural; Generalitat Valenciana; AGENCIA ESTATAL DE INVESTIGACION[EN] In Citrus, the response to environmental floral inductive signals is inhibited by the presence of developing fruits. The mechanism involves epigenetic activation of the CcMADS19 locus (FLC orthologue), encoding a floral repressor. To understand how this epigenetic regulation is reverted to allow flowering in the following season, we have forced precocious sprouting of axillary buds in fruit-bearing shoots, and examined the competence to floral inductive signals of old and new leaves derived from them. We have found that CcMADS19 is enriched in repressive H3K27me3 marks in young, but not old leaves, revealing that axillary buds retain a silenced version of the floral repressor that is mitotically transmitted to the newly emerging leaves, which are able to induce flowering. Therefore, we propose that flowering in Citrus is necessarily preceded by vegetative sprouting, so that the competence to respond to floral inductive signals is reset in the new leaves.
- PublicationInhibiting the inhibitor to allow flowering in Citrus: the seasonal epigenetic resetting of CcMADS19(International Society for Horticultural Science (ISHS), 2022) Mesejo Conejos, Carlos; Marzal, A.; Martínez Fuentes, Amparo; Reig Valor, Carmina; de Lucas, M.; Blazquez Rodriguez, Miguel Angel; Agustí Fonfría, Manuel; Dpto. de Producción Vegetal; Instituto Universitario Mixto de Biología Molecular y Celular de Plantas; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural; Generalitat Valenciana; Agencia Estatal de Investigación[EN] Citrus trees are polycarpic species that only produce single flowers or determinate inflorescences, so that vegetative growth is required at the axillary buds to renew the polycarpic habit. In addition, in some species/cultivars the presence of fruits inhibits sprouting and flower induction from nearby axillary buds in the current season. This results in low flowering intensity the following spring, thus giving rise to alternate bearing. Our previous results show that the presence of the fruit correlates with epigenetic changes in CcMADS19 (Citrus clementina FLC ortholog), which prevent the activation of the floral promoter CiFT3 (Citrus clementina FT ortholog) in the leaf, even in the presence of the floral inductive signals (i.e., cold temperatures). To reestablish the flowering ability, the axillary bud maintains a silenced version of CcMADS19 which is mitotically transmitted to the new vegetative shoots, thereby allowing the activation of CiFT3 during the following cold season. This mechanism operates through changes in H3K27me3 and methyltransferase activity. On the other hand, gibberellin (GAs) have always been considered the main flowering inhibitor in Citrus. But, how are GAs related to the CcMADS19 transcription factor? Our results show no relationship between GAs and CcMADS19 gene expression, and suggest that GAs act downstream of CcMADS19. In this paper, we converge the hormonal hypothesis with the genetic and epigenetic evidences in the control of Citrus flowering. In summary, we propose the view of flowering as a repressive process: new buds are competent to flower, but this default state is reversed -or transiently repressed- by inhibitory signals (due to fruit). And the promotion of flowering would involve the upstream repression of this inhibition. In other words, the so-called ¿promoters of flowering¿ might be ¿inhibitors of flowering inhibitors¿.
- PublicationAdvances in Citrus Flowering: A Review(Frontiers Media SA, 2022-04-08) Agustí Fonfría, Manuel; Reig Valor, Carmina; Martínez Fuentes, Amparo; Mesejo Conejos, Carlos; Dpto. de Producción Vegetal; Instituto Agroforestal Mediterráneo; Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural[EN] Citrus are polycarpic and evergreen species that flower once in spring or several times a year depending on the genotype and the climatic conditions. Floral induction is triggered by low temperature and water-deficit stress and occurs 2-3 months before bud sprouting, whereas differentiation takes place at the same time as sprouting. The induced buds develop single flowers or determinate inflorescences, so that vegetative growth is required at the axillary buds to renew the polycarpic habit. The presence of fruits inhibits sprouting and flower induction from nearby axillary buds in the current season. In some species and cultivars, this results in low flowering intensity the following spring, thus giving rise to alternate bearing. A number of key flowering genes act in the leaf (CiFT3, CcMADS19, etc.) or in the bud (CsLFY, CsTFL1, etc.) to promote or inhibit both flowering time and reproductive meristem identity in response to these climatic factors, the fruit dominance, or the age of the plant (juvenility). The expression of some of these genes can be modified by gibberellin treatments, which reduce bud sprouting and flowering in adult trees, and constitute the main horticultural technique to control flowering in citrus. This review presents a comprehensive view of all aspects of the flowering process in citrus, converging the research published during the past half century, which focused on plant growth regulators and the nutritional source-sink relationships and guided research toward the study of gene transcription and plant transformation, and the advances made with the development of the tools of molecular biology published during the current century.