Effect of Exogenous Auxin Treatment on Cell Wall Polymers of Strawberry Fruit.

The role of auxin in the fruit-ripening process during the early developmental stages of commercial strawberry fruits (Fragaria x ananassa) has been previously described, with auxin production occurring in achenes and moving to the receptacle. Additionally, fruit softening is a consequence of the depolymerization and solubilization of cell wall components produced by the action of a group of proteins and enzymes. The aim of this study was to compare the effect of exogenous auxin treatment on the physiological properties of the cell wall-associated polysaccharide contents of strawberry fruits. We combined thermogravimetric (TG) analysis with analyses of the mRNA abundance, enzymatic activity, and physiological characteristics related to the cell wall. The samples did not show a change in fruit firmness at 48 h post-treatment; by contrast, we showed changes in the cell wall stability based on TG and differential thermogravimetric (DTG) analysis curves. Less degradation of the cell wall polymers was observed after auxin treatment at 48 h post-treatment. The results of our study indicate that auxin treatment delays the cell wall disassembly process in strawberries.

Structural and transcriptional characterization of pyruvate decarboxylase (PDC) gene family during strawberry fruit ripening process.

Strawberry is one of the most popular fruits in the world, because their high fruit quality, especially with respect to the combination of aroma, flavor, color, and nutritional compounds. Pyruvate decarboxylase (PDC) is the first of two enzymes specifically required for ethanolic fermentation and catalyzes the decarboxylation of pyruvate to yield acetaldehyde and CO2. The ethanol, an important alcohol which acts as a precursor for the ester and other alcohols formation in strawberry, is produced by the PDC. The objective was found all different PDCs genes present in the strawberry genome and investigate PDC gene expression and ligand-protein interactions in strawberry fruit. Volatile organic compounds were evaluated during the development of the fruit. After this, eight FaPDC were identified with four genes that increase the relative expression during fruit ripening process. Molecular dynamics simulations were performed to analyze the behavior of Pyr and TPP ligands within the catalytic and regulatory sites of the PDC proteins. Results indicated that energy-restrained simulations exhibited minor fluctuations in ligand-protein interactions, while unrestrained simulations revealed crucial insights into ligand affinity. TPP consistently displayed strong interactions with the catalytic site, emphasizing its pivotal role in enzymatic activity. However, FaPDC6 and FaPDC9 exhibited decreased pyruvate affinity initially, suggesting unique binding characteristics requiring further investigation. Finally, the present study contributes significantly to understanding PDC gene expression and the intricate molecular dynamics underlying strawberry fruit ripening, shedding light on potential targets for further research in this critical biological pathway.

Ugni molinae Fruit as a Source of Bioactive Compounds with Good Quality Traits.

Since the intake of fruits and vegetables displays important effects on the incidence of several chronic diseases in humans, consumers' attention worldwide is focused on the identification of functional foods. In this sense, Ugni molinae (murtilla or murta fruit) is an important source of molecules with a strong antioxidant capacity that is widely used as a medicinal plant in Southern Argentina-Chile. Research on murtilla berries showed that this fruit and its leaves can be an excellent source of polyphenols and bioactive compounds with antibacterial and antioxidant capacity. This review is aimed at providing valuable information and discussing the available literature focused on four principal points: (i) fruit quality and plant physiology, (ii) compound content with bioactive properties, (iii) health properties for consumers of the fruit and leaves, and (iv) challenges for future research. Based on these four points, we propose that murtilla fruit can be a potential ingredient for new functional food products.

Molecular and structural insights into FaEXPA5, an alpha-expansin protein related with cell wall disassembly during ripening of strawberry fruit.

Cell wall modification is one of the main factors that produce the tissue softening during ripening of many fruit including strawberry (Fragaria x ananassa). Expansins have been studied for over 20 years as a class of the important cell growth regulators, and in the last years these have been related with the fruit softening. In strawberry, five partial sequences of the expansins genes were described in the past, this analysis showed that FaEXP5 partial gene was present throughout fruit development, but was more strongly expressed during ripening. Now, we reported the full length of this α-expansin (FaEXPA5), whose had been related with fruit softening, and the protein structural was described by homology model. Their transcript accumulation during softening was confirmed by qRT-PCR, displaying a high accumulation rate during fruit ripening. In silico analysis of promoter sequence showed four ABA and two auxin cis-regulatory elements, potentially responsible for the expression patterns observed in response to the hormone treatments. Additionally, 3D protein model displayed two domains and one open groove characteristic of expansin structures. The protein-ligand interactions were evaluated by molecular dynamic (MD) simulation using three different long structure ligands (a cellulose fiber, a xyloglucan fiber (XXXG type), and a pectin fiber as control). Favorable interactions were observed with xyloglucan and cellulose, being cellulose the best ligand with lower RMSD value. Additionally, MD simulations showed that FaEXPA5 can interact with the ligands through residues present in the open groove along the two domains.

Molecular Insights into FaEG1, a Strawberry Endoglucanase Enzyme Expressed during Strawberry Fruit Ripening.

The endo-ß-1,4-glucanases (EGs) that belong to the glycosyl hydrolase family 9 (GH9) have roles in cell wall synthesis, remodeling and degradation. Previous studies have suggested that EGs may play a key role in the ripening of different fruits including strawberries. In this study, we used reverse-transcription quantitative polymerase chain reaction (RT-qPCR) assays to determine the transcript accumulation of an endo-ß-1,4-glucanase (FaEG1) during fruit development in two different strawberry 'Camarosa' and 'Monterey' with contrasting softening ratios. Phylogenetic analyses suggest that FaEG1 belongs to the α group of the GH9 family with other proteins previously described with roles in elongation, abscission and ripening. Comparative modeling was used to obtain the FaEG1 structure. The model displays a α-barrel-type structure that is typical of the GH9 enzyme family, and comprises 12 α-helices, 2 310 helices and 6 ß-sheets. The catalytic residues were oriented to the solvent in the middle of an open groove. Protein-ligand interactions were explored with cellulose and two xyloglucans as ligands; the results suggest that the FaEG1-cellulose and FaEG1-XXXGXXXG (the most abundant xyloglucan in strawberries) complexes were more stable complexes than XXFGXXFG. The cell wall degradation was observed by scanning electron microscopy (SEM). The data are congruent with the probable role of the FaEG1 protein in the dissembly of the cellulose-hemicellulose fraction during the ripening of strawberry fruit.

Understanding the roles of Lys33 and Arg45 in the binding-site stability of LjLTP10, an LTP related to drought stress in Lotus japonicus.

In Lotus japonicus, as in most plants, long-chain fatty acids are important components of cuticular wax, one of the principal functions of which is to act as a barrier to water loss in response to drought stress. It is thought that lipid transfer proteins (LTPs) are involved in the process of cuticle formation. We previously described LjLTP10 as an LTP involved in cuticle formation during acclimation response to drought stress in L. japonicus. The structural model of LjLTP10 had two residues (K33 and R45) in the hydrophobic cavity, although the role of these residues was unclear. In the present work, we investigated the molecular mechanism involved in the transport of lipid precursors in L. japonicus and clarified the importance of the residues K33 and R45. First, in silico site-directed mutagenesis studies were carried out on the LjLTP10 structure. Structural analysis showed that LjLTP10 mutants possess similar structures but their hydrophobic cavities are somewhat different. Unfavorable energies for the interactions of the mutant proteins with different ligands were found by molecular docking and molecular dynamics simulations. We also examined the contributions of energetic parameters to the free energy of the protein-ligand complex using the MM-GBSA method. Results showed that the different complexes present similar, favorable van der Waals interactions, whereas electrostatic interactions were not favored in the mutant structures. Our study indicates that the residues K33 and R45 play a crucial role in maintaining the binding pocket structure required for lipid transport.

Linking the platelet antiaggregation effect of different strawberries species with antioxidants: metabolomic and transcript profiling of polyphenols / Asociando el efecto de antiagregación plaquetaria de distintas especies de frutillas con antioxidantes: perfil metabolómico y transcriptómico de polifenoles

A comparative study of antioxidant properties, platelet antiaggregation activity and transcriptional analysis of flavonoid biosynthesis genes were performed in Fragaria x ananassa, F. vesca and F. chiloensis subsp chiloensis f. chiloensis and f. patagonica. Furthermore, differences in flavonoid content were found by UHPLC-MS. The highest free radical scavenging activity by DPPH assay was observed in F. chiloensis f. chiloensis, meanwhile, F. vesca presented the highest antioxidant capacity by FRAP. Biosynthetic flavonoids- related transcripts were higher abundant in F. x ananassa and lower in F. vesca. Additionally, all strawberry extracts showed antiaggregant effect (1 mg mL-1), but F. vesca and F. chiloensis subsp. chiloensis f. patagonica were still active at lower concentration. This study suggests that platelet antiaggregation effect of different strawberries could be due to isoflavones and flavonoids precursors in addition to anthocyanins. Results could usefully to take decisions in future breeding programs to improve the content of healthy compounds in strawberry fruits.

Se realizó un estudio comparativo de propiedades antioxidantes, actividad de antiagregacion plaquetaria, análisis transcripcional de genes de biosíntesis de flavonoides y contenido de estos en Fragaria x ananassa, F. vesca and F. chiloensis subsp chiloensis f. chiloensis and f. patagonica. La mayor actividad removedora de radicales libres por DPPH se observó en F. chiloensis f. chiloensis, mientras F. vesca presentó la mayor capacidad antioxidante mediante FRAP. Transcritos relacionados con biosíntesis de flavonoides fueron mas abundantes en F. x ananassa y menores en F. vesca. Adicionalmente, todos los extractos de frutillas mostraron efectos antiagregante (1 mg mL-1), pero F. vesca and F. chiloensis subsp. chiloensis f. patagonica fueron activos a concentraciones menores. Este estudio sugiere que efectos de antiagregación plaquetaria en distintas frutillas podría deberse a isoflavonas y precursores de flavonoides además de antocianinas. Los resultados podrían ser útiles en programas de mejoramiento genético para mejorar el contenido de compuestos saludables en frutilla.