RESUMEN
The influence of cell morphology on the textural characteristic of freeze-dried apple, strawberry, and mango cubes was evaluated. Corresponding restructured cube samples without intact cell morphology were prepared as controls. Results indicated that the presence of cell morphology strengthened the shrinkage and collapse of samples during freeze-drying, especially in mangoes due to the high content of sugar. Intact cell morphology was found in natural fruit cubes after freeze-drying by scanning electron microscopy (SEM) observation, making them exhibit a more regular microporous structure, further resulting in higher hardness than the restructured cubes. However, the intact cell morphology negatively affected the crispness of freeze-dried cubes since it enhanced structural collapse. The freeze-dried samples without cell morphology would destroy the cellulose structure and form a continuous open-pore structure under the concentration effect of ice crystals during freezing, which accelerates the escape of water molecules, increases the drying rate, and avoid collapse. Sensory experiments found that restructured cubes without intact cell morphology exhibited greater comprehensive acceptance, suggesting the potential application of cell morphology disruption in the future freeze-drying industry.
Asunto(s)
Fragaria , Liofilización , Malus , Mangifera , Células Vegetales , Fragaria/química , Fragaria/ultraestructura , Liofilización/métodos , Frutas/química , Frutas/ultraestructura , Malus/química , Malus/ultraestructura , Mangifera/química , Mangifera/ultraestructura , Células Vegetales/química , Células Vegetales/ultraestructura , Microscopía Electroquímica de RastreoRESUMEN
MicroRNAs (miRNAs) are a kind of short noncoding RNA (20-24 nt), playing versatile roles in plant growth and development. Strawberry generates leaves and flowers with unique features. However, few miRNAs have been functionally characterised in strawberry, especially for their developmental regulation. Here, we identified one ethyl methanesulfonate (EMS) mutant, deeply serrated (des), in the woodland strawberry Fragaria vesca that has wrinkled leaves with deeper serrations, serrated petals and deformed carpels. The causative mutation occurs in the 19th nucleotide of the FvemiR164a mature sequence. Overexpressing FveMIR164A rescued the phenotypes of des/fvemir164a except the petal serrations. Furthermore, we identified two allelic mutants of FveCUC2a, one target of FvemiR164a, which developed leaves with smooth margins and fused leaflets. Phenotypes of the double mutant fvemir164a fvecuc2a indicated that the two genes act linearly in leaf and carpel development, but synergistically in the development of other floral organs and inflorescence architecture. This work demonstrates the conserved and novel roles of the miR164-CUC2 module in leaf and flower development in different plant species, and reveals that the 19th nucleotide of FvemiR164a is important for its processing.
Asunto(s)
Secuencia Conservada/genética , Flores/anatomía & histología , Flores/genética , Fragaria/genética , MicroARNs/genética , Hojas de la Planta/anatomía & histología , Hojas de la Planta/genética , Proteínas de Plantas/metabolismo , Secuencia de Bases , Flores/crecimiento & desarrollo , Flores/ultraestructura , Fragaria/anatomía & histología , Fragaria/crecimiento & desarrollo , Fragaria/ultraestructura , Genes de Plantas , MicroARNs/metabolismo , Nucleótidos/genética , Fenotipo , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/ultraestructura , Proteínas de Plantas/genética , Mutación Puntual/genéticaRESUMEN
Due to its organoleptic and nutraceutical qualities, strawberry fruit (Fragaria x ananassa, Duch) is a worldwide important commodity. The role of ethylene in the regulation of strawberry cell wall metabolism was studied in fruit from Toyonoka cultivar harvested at white stage, when most changes associated with fruit ripening have begun. Fruit were treated with ethephon, an ethylene-releasing reagent, or with 1-methylcyclopropene (1-MCP), a competitive inhibitor of ethylene action, maintaining a set of non-treated fruit as controls for each condition. Ethephon treated-fruit showed higher contents of hemicelluloses, cellulose and neutral sugars regarding controls, while 1-MCP-treated fruit showed a lower amount of those fractions. On the other hand, ethephon-treated fruit presented a lower quantity of galacturonic acid from ionically and covalently bound pectins regarding controls, while 1-MCP-treated fruit showed higher contents of those components. We also explored the ethylene effect over the mRNA accumulation of genes related to pectins and hemicelluloses metabolism, and a relationship between gene expression patterns and cell wall polysaccharides contents was shown. Moreover, we detected that strawberry necrotrophic pathogens growth more easily on plates containing cell walls from ethephon-treated fruit regarding controls, while a lower growth rate was observed when cell walls from 1-MCP treated fruit were used as the only carbon source, suggesting an effect of ethylene on cell wall structure. Around 60% of strawberry cell wall is made up of pectins, which in turns is 70% made by homogalacturonans. Our findings support the idea of a central role for pectins on strawberry fruit softening and a participation of ethylene in the regulation of this process.
Asunto(s)
Pared Celular/metabolismo , Etilenos/farmacología , Fragaria/metabolismo , Reguladores del Crecimiento de las Plantas/farmacología , Metabolismo de los Hidratos de Carbono/efectos de los fármacos , Celulosa/metabolismo , Etilenos/metabolismo , Fragaria/microbiología , Fragaria/ultraestructura , Frutas/genética , Frutas/crecimiento & desarrollo , Frutas/ultraestructura , Interacciones Huésped-Patógeno/efectos de los fármacos , Pectinas/genética , Pectinas/metabolismo , Reguladores del Crecimiento de las Plantas/metabolismo , Polisacáridos/metabolismo , ARN Mensajero/metabolismoRESUMEN
To ascertain the role of pectin disassembly in fruit softening, chelated- (CSP) and sodium carbonate-soluble (SSP) pectins from plants with a pectate lyase, FaplC, or a polygalacturonase, FaPG1, downregulated by antisense transformation were characterized at the nanostructural level. Fruits from transgenic plants were firmer than the control, although FaPG1 suppression had a greater effect on firmness. Size exclusion chromatography showed that the average molecular masses of both transgenic pectins were higher than that of the control. Atomic force microscopy analysis of pectins confirmed the higher degree of polymerization as result of pectinase silencing. The mean length values for CSP chains increased from 84 nm in the control to 95.5 and 101 nm, in antisense FaplC and antisense FaPG1 samples, respectively. Similarly, SSP polyuronides were longer in transgenic fruits (61, 67.5 and 71 nm, in the control, antisense FaplC and antisense FaPG1 samples, respectively). Transgenic pectins showed a more complex structure, with a higher percentage of branched chains than the control, especially in the case of FaPG1 silenced fruits. Supramolecular pectin aggregates, supposedly formed by homogalacturonan and rhamnogalacturonan I, were more frequently observed in antisense FaPG1 samples. The larger modifications in the nanostructure of pectins in FaPG1 silenced fruits when compared with antisense pectate lyase plants correlate with the higher impact of polygalacturonase silencing on reducing strawberry fruit softening.
Asunto(s)
Fragaria/metabolismo , Pectinas/metabolismo , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente/metabolismo , Poligalacturonasa/metabolismo , Polisacárido Liasas/metabolismo , Fragaria/química , Fragaria/genética , Fragaria/ultraestructura , Silenciador del Gen , Pectinas/química , Pectinas/ultraestructura , Proteínas de Plantas/genética , Plantas Modificadas Genéticamente/química , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/ultraestructura , Poligalacturonasa/genética , Polisacárido Liasas/genéticaRESUMEN
The elemental composition of strawberry plants (Fragaria ananassa cv. Macarena) inoculated with the plant growth-promoting bacterium Azospirillum brasilense REC3, and non-inoculated controls, was studied using scanning electron microscopy (SEM) and energy dispersive X-ray (EDS) analysis. This allowed simultaneous semi-quantification of different elements in a small, solid sample. Plants were inoculated and grown hydroponically in 50% or 100% Hoagland solution, corresponding to limited or optimum nutrient medium, respectively. Bacteria-inoculated plants increased the growth index 45% and 80% compared to controls when grown in 100% and 50% Hoagland solution, respectively. Thus, inoculation with A. brasilense REC3 in a nutrient-limited medium had the strongest effect in terms of increasing both shoot and root biomass and growth index, as already described for Azospirillum inoculated into nutrient-poor soils. SEM-EDS spectra and maps showed the elemental composition and relative distribution of nutrients in strawberry tissues. Leaves contained C, O, N, Na, P, K, Ca and Cu, while roots also had Si and Cl. The organic fraction (C, O and N) accounted for over 96.3% of the total chemical composition; of the mineral fraction, Na had higher accumulation in both leaves and roots. Azospirillum-inoculated and control plants had similar elemental quantities; however, in bacteria-inoculated roots, P was significantly increased (34.33%), which constitutes a major benefit for plant nutrition, while Cu content decreased (35.16%).
Asunto(s)
Azospirillum brasilense/fisiología , Fragaria/química , Fragaria/microbiología , Fragaria/crecimiento & desarrollo , Fragaria/ultraestructura , Microscopía Electrónica de Rastreo , Hojas de la Planta/química , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/microbiología , Hojas de la Planta/ultraestructura , Raíces de Plantas/química , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/microbiología , Raíces de Plantas/ultraestructura , Espectrometría por Rayos XRESUMEN
Antisense-mediated down-regulation of the fruit-specific polygalacturonase (PG) gene FaPG1 in strawberries (Fragaria×ananassa Duch.) has been previously demonstrated to reduce fruit softening and to extend post-harvest shelf life, despite the low PG activity detected in this fruit. The improved fruit traits were suggested to be attributable to a reduced cell wall disassembly due to FaPG1 silencing. This research provides empirical evidence that supports this assumption at the biochemical, cellular, and tissue levels. Cell wall modifications of two independent transgenic antisense lines that demonstrated a >90% reduction in FaPG1 transcript levels were analysed. Sequential extraction of cell wall fractions from control and ripe fruits exhibited a 42% decrease in pectin solubilization in transgenic fruits. A detailed chromatographic analysis of the gel filtration pectin profiles of the different cell wall fractions revealed a diminished depolymerization of the more tightly bound pectins in transgenic fruits, which were solubilized with both a chelating agent and sodium carbonate. The cell wall extracts from antisense FaPG1 fruits also displayed less severe in vitro swelling. A histological analysis revealed more extended cell-cell adhesion areas and an enhanced tissue integrity in transgenic ripe fruits. An immunohistological analysis of fruit sections using the JIM5 antibody against low methyl-esterified pectins demonstrated a higher labelling in transgenic fruit sections, whereas minor differences were observed with JIM7, an antibody that recognizes highly methyl-esterified pectins. These results support that the increased firmness of transgenic antisense FaPG1 strawberry fruits is predominantly due to a decrease in pectin solubilization and depolymerization that correlates with more tightly attached cell wall-bound pectins. This limited disassembly in the transgenic lines indicates that these pectin fractions could play a key role in tissue integrity maintenance that results in firmer ripe fruit.
Asunto(s)
Fragaria/genética , Regulación Enzimológica de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Proteínas de Plantas/genética , Poligalacturonasa/genética , Pared Celular/genética , Pared Celular/metabolismo , Pared Celular/ultraestructura , Cromatografía en Gel , Regulación hacia Abajo , Electroforesis en Gel de Poliacrilamida , Fragaria/metabolismo , Fragaria/ultraestructura , Frutas/genética , Frutas/metabolismo , Frutas/ultraestructura , Silenciador del Gen , Microscopía Electrónica de Rastreo , Pectinas/metabolismo , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/metabolismo , Plantas Modificadas Genéticamente/ultraestructura , Poligalacturonasa/metabolismoRESUMEN
The diploid woodland strawberry, Fragaria vesca, is being recognized as a model for the more complex octoploid commercial strawberry, Fragaria × ananassa. F. vesca exhibits a short seed to seed cycle, can be easily transformed by Agrobacteria, and a draft genome sequence has been published. These features, together with its similar flower structure, potentially make F. vesca a good model for studying the flower development of other members of the Rosaceae family, which contains many economically important fruit trees and ornamental plants. To propel F. vesca's role in genetic and genomic research and to facilitate the study of its reproductive development, we have investigated in detail F. vesca flower and early fruit development using a seventh generation inbred diploid line, Yellow Wonder 5AF7. We present here standardized developmental staging and detailed descriptions of morphological changes associated with flower and early fruit development based on images of hand dissected flowers, histological sections, and scanning electron microscopy. In situ hybridization with the F. vesca AGAMOUS homolog, FvAG, showed expression in young stamen and carpel primordia. This work lays the essential groundwork and standardization for future molecular, genetic, and genomic studies of F. vesca.
Asunto(s)
Diploidia , Flores/crecimiento & desarrollo , Flores/genética , Fragaria/crecimiento & desarrollo , Fragaria/genética , Frutas/crecimiento & desarrollo , Frutas/genética , Flores/anatomía & histología , Flores/ultraestructura , Fragaria/ultraestructura , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Genes de Plantas/genética , Hibridación in Situ , Especificidad de Órganos , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Brotes de la Planta/anatomía & histología , Brotes de la Planta/crecimiento & desarrollo , Brotes de la Planta/ultraestructura , ReproducciónRESUMEN
Ultrastructural aspects of leaf epicuticular wax structures were investigated in the garden strawberry Fragariaxananassa by scanning and transmission electron microscopy. Both the adaxial and abaxial surfaces of two cultivars (Maehyang and Red Pearl) were collected and subjected to surface observations and ultrathin sections. The most prominent leaf epicuticular wax structures included membraneous platelets and angular rodlets. Most wax platelets were membraneous, and appeared to protrude from the surface at an acute angle. Angular rodlets were usually bent and had rather distinct facets in the abaxial surface of the two cultivars. Membraneous platelets were predominant on the adaxial surface of Maehyang, whereas the adaxial surface of Red Pearl was characterized by angular rodlets. However, both cultivars possessed angular rodlets on the abaxial surface, simultaneously. The combination of air-drying without vacuum and in-lens imaging of secondary electron signals with a field emission gun could impart the superb resolution at low electron dose with minimal specimen shrinkage. In vertical profiles of the leaf epidermis, epicuticular waxes were observed above the cuticle layer, and measured approximately as 50nm in thickness. The natural epicuticular waxes were seemingly mixtures of electron-dense microfibrils, and heterogeneous in shape on ultrathin sections. Distinct crystal-like strata could be hardly discernable in the wax structures. These results suggest that the garden strawberry has the nature of syntopism within one plant and polymorphism within the same species in the formation and occurrence of leaf epicuticular waxes.
Asunto(s)
Fragaria/ultraestructura , Epidermis de la Planta/ultraestructura , Hojas de la Planta/ultraestructura , Microscopía Electrónica de Rastreo/métodos , Microscopía Electrónica de Transmisión , Ceras/análisisRESUMEN
Strawberry cultivars differ in their sensitivity to NaCl; fruits of cv. Elsanta suffer from softening, whereas those of cv. Korona retain their firmness. The mean fruit fresh weight is reduced in cv. Elsanta up to 46% and in cv. Korona up to 26%. Cell walls of fruits grown under 0, 40, or 80 mmol/L NaCl were extracted and analyzed. In fruits of cv. Korona, the content of the alcohol-insoluble residue remained comparatively stable as salt levels increased but was reduced in cv. Elsanta. The water-soluble pectin fraction was not affected in cv. Korona, but the content of low methoxy pectinates increased significantly, indicative of the generation of calcium and magnesium bridges that stabilize pectin polysaccharides of cell walls. In cv. Elsanta, the content of water-soluble pectin rose, indicating pectin solubilization. For both cultivars, the significant negative correlation of fruit Cl(-) contents with the contents of NaOH-soluble pectinates, when expressed per fruit fresh mass, indicated that covalently bound pectic substances were degraded. Especially the response of cv. Elsanta is in line with the general observation that severe osmotic stress results in slower cell expansion and weaker cell walls.
Asunto(s)
Pared Celular/química , Fragaria/ultraestructura , Frutas/ultraestructura , Cloruro de Sodio/administración & dosificación , Pared Celular/efectos de los fármacos , Celulosa/análisis , Concentración Osmolar , Presión Osmótica , Pectinas/análisis , Especificidad de la EspecieRESUMEN
The effects of the cuticle and epicuticular waxes of grapefruit, strawberry and apple on the photodegradation and penetration of chlorpyrifos-methyl were studied. Photodegradation experiments were conducted by exposing the insecticide to the light of a xenon lamp in the presence of a film of wax extracted from the fruit surface. The half-life of chlorpyrifos-methyl irradiated in absence of waxes was 9.6 min. The half-lives of pesticide irradiated in the presence of wax extracts of apple, grapefruit and strawberry were 83, 34 and 26 min, respectively. In penetration studies, fruit with and without wax layers were treated with an aqueous suspension of pesticide. The penetration of the pesticide from the cuticle to the pulp was measured after 24 h. Samples without wax contained a higher total amount of insecticide than those with wax. No pesticide was detected in samples of apple and grapefruit pulp. Residues were detected in all fractions of strawberry. The waxes and cuticle appear to have some effect on the photodegradation and penetration of chlorpyrifos-methyl in fruit samples.
Asunto(s)
Cloropirifos/análogos & derivados , Contaminación de Alimentos/análisis , Frutas/química , Residuos de Plaguicidas/análisis , Ceras , Cloropirifos/análisis , Citrus/química , Citrus/ultraestructura , Análisis de los Alimentos/métodos , Alimentos Orgánicos/análisis , Fragaria/química , Fragaria/ultraestructura , Semivida , Humanos , Luz , Malus/química , Malus/ultraestructura , Microscopía Electrónica de Rastreo , Propiedades de SuperficieRESUMEN
Phospholipase D alpha (PLD, EC 3.1.4.4)) is a key enzyme involved in membrane deterioration that occurs during fruit ripening and senescence. The biochemical and molecular characteristics of PLD was studied in strawberry (Fragaria ananassa Duch) fruits, which are non-climacteric fruits. PLD activity was primarily associated with the mitochondrial and microsomal fractions and showed increased activity during development. Optimal pH levels of activity were observed at 5.5 and 6.5 for mitochondrial PLD and at 5 and 7 for microsomal PLD. Calcium enhanced microsomal PLD activity at 1-40 microM levels. PLD activity followed Michaelis-Menten kinetics. Lineweaver-Burk analysis gave Km values in the range of 114 and 277 microM using dipalmitoylphosphatidylcholine (DPPC) as substrate for mitochondrial and microsomal PLD, respectively. The Vmax value for the microsomal PLD was nearly 12-fold higher than that of mitochondrial PLD. A 2874 bp full-length cDNA for PLD alpha was amplified from strawberry fruit mRNA using RT-PCR and 5'- and 3'-RACE encoding an 810 amino acid-polypeptide. The predicted strawberry PLD sequence showed the characteristic C2 domain and the phospholipase domains conferring calcium sensitivity and the enzyme activity, respectively. The strawberry PLD alpha showed a high degree of similarity to other PLD alphas from plants. The implications of PLD regulation during ripening of fruits are discussed.