Ripening of grape (
Vitis vinifera L.) berry immediately precedes harvesting and the evolution of the skin tissue is important as it contains the key compounds for wine quality. Grape softening is ...thought to result from extensive cell wall modifications that occur during ripening. These modifications result from the activity of different cell wall-modifying enzymes. Two of the most significant pectin-degrading enzymes are pectin methylesterase (EC 3.1.1.11) and polygalacturonase (EC 3.2.1.15). In this work, the activities of both enzymes were monitored in skin tissue throughout berry development. Pectin methylesterase activity was present before the onset of veraison and increased during skin maturation. No polygalacturonase activity could be detected. The accumulation of mRNA encoding a pectin methylesterase and two polygalacturonase isoforms was examined using RT–PCR. Transcripts for pectin methylesterase were present in all stages analyzed with a maximal accumulation at the end of color change. Accumulation of
VvPG1 transcript was closely correlated with berry softening, and expression of this gene was markedly increased during the color change.
VvPG2 mRNA accumulation began before veraison and was low during skin ripening. A phylogenic analysis showed that this gene is classified in a different group than
VvPG1. These findings suggest that both genes are associated with different mechanisms during skin development.
VvPG1, in particular, is most likely to play a role in skin softening and
VvPG2 in triggering the ripening process.
This work investigated the structural and biochemical changes during grape berry development which account potentially for the onset and increase in susceptibility to Botrytis cinerea. Using the cv. ...Sauvignon blanc, we quantified at seven developmental growth stages from herbaceous to over-mature berries: (1) fruit ontogenic resistance using three strains (II-transposa), (2) the morphological and maturity fruit characteristics and (3) preformed biochemical compounds located in the berry skin. From the mid-colour change stage onwards, susceptibility of unwounded fruit increased sigmoidally in both rot and sporulation severities at the berry surface. A principal component analysis identified a very close connection between fruit susceptibility and the level of fruit maturity. Berry susceptibility was significantly and positively correlated with the phenolic compounds in the skin cell walls and negatively correlated with the total tannin content in the skin and with water activity (Aw) at the fruit surface. On the berry, Aw decreased from 0.94 at bunch closure to 0.89 at berry maturity, with a relatively low value (0.90) at the stage of mid-colour change. Using artificial media, different Aw levels led to significant differences in mycelial growth (Aw ≤0.95 resulted in the lowest growth rate ≤0.34 mm day⁻¹). Thus, besides the level of fruit maturity, both water activity on the fruit and the total tannin content in the skin may affect fungal growth and berry colonisation. The potential of these variables for use as indicators of grape berry susceptibility as well as associated mechanisms for the development of disease are discussed.
Aims: The objective was to better understand the mechanisms involved in grape ripening that brings about important changes in the physiology and chemistry of the fruit. So we focused on the ...involvement of two growth regulators: abscisic acid (ABA) and indol-acetic acid (IAA) in controlling grape berry ripening process. Methods and results: We described the evolution of the two plant growth regulators during the development of cv. Merlot grapes (Vitis vinifera L.). In order to better understand the role of ABA and IAA in the ripening control, these two growth regulators were applied on the grapes at the onset of veraison. The hormonal profile was established on treated berries and different physiological parameters were assayed to evaluate the effects of both applications. The partitioning of both plant growth regulators in nontreated berries showed that ABA and IAA accumulated at the onset of ripening. Moreover, it appeared that endogenous ABA decreased progressively in the flesh while accumulated in the skin from the beginning of the colour change to maturity. The hormonal treatments modified the hormonal profile and several physiological parameters: sugar, acidity, colour, and Botrytis sensibility. Conclusion: These findings suggest that both treatments have modified the ripening process. Exogenous ABA has induced advancement in grape ripening, while IAA application has delayed this process. These observations support the view that the grape ripening process may be influenced by the hormonal status. Significance and impact of study: This study gives new information about the ripening control of the non-climacteric fruits. In grape berries, it provides evidence of a possible co-involvement of ABA and IAA in controlling ripening process.
Proteome analysis of grape skins during ripening Deytieux, Christelle; Geny, Laurence; Lapaillerie, Delphine ...
Journal of experimental botany,
01/2007, Letnik:
58, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The characterization of proteins isolated from skin tissue is apparently an essential parameter for understanding grape ripening as this tissue contains the key compounds for wine quality. It has ...been particularly difficult to extract proteins from skins for analysis by two-dimensional electrophoresis gels and, therefore, a protocol for this purpose has been adapted. The focus was on the evolution of the proteome profile of grape skin during maturation. Proteome maps obtained at three stages of ripening were compared to assess the extent to which protein distribution differs in grape skin during ripening. The comparative analysis shows that numerous soluble skin proteins evolve during ripening and reveal specific distributions at different stages. Proteins involved in photosynthesis, carbohydrate metabolisms, and stress response are identified as being over-expressed at the beginning of colour-change. The end of colour-change is characterized by the over-expression of proteins involved in anthocyanin synthesis and, at harvest, the dominant proteins are involved in defence mechanisms. In particular, increases in the abundance of different chitinase and β-1,3-glucanase isoforms were found as the berry ripens. This observation can be correlated with the increase of the activities of both of these enzymes during skin ripening. The differences observed in proteome maps clearly show that significant metabolic changes occur in grape skin during this crucial phase of ripening. This comparative analysis provides more detailed characterization of the fruit ripening process.
The phytopathogenic fungus
Botrytis cinerea produces a set of polygalacturonases (PGs) which are involved in the enzymatic degradation of pectin during plant tissue infection. Two polygalacturonases ...secreted by
B. cinerea in seven-day-old liquid culture were purified to apparent homogeneity by chromatography. PG I was an exopolygalacturonase of molecular weight 65 kDa and pI 8.0 and PG II was an endopolygalacturonase of 52 kDa and pI 7.8. Enzymatic activity of PG I and PG II was partially inhibited by 1 mM CaCl
2, probably by calcium chelation of polygalacturonic acid, the substrate of the enzyme.
Aim: To better understand the protein composition of grape skin cell walls, we have developed a method to analyse the strongly bound cell wall proteins. Methods and results: The protocol was ...developed with grape skins at full maturity. The critical steps of this protocol were : (i) the elimination of cellular aggregates, (ii) the elimination of soluble proteins, and (iii) the localization of the identified proteins within the cell wall. To verify whether these three conditions were met, the decrease in the quantity of cellular aggregates was followed by optical microscopy, the removal of soluble proteins was measured by chemical assay, and the presence of proteins located in cell walls was demonstrated by extensive bioinformatic analysis. The process made it possible to obtain a four-fold reduction in the amount of cellular aggregates, a reduction in the concentration of soluble proteins below the method detection limit, and a high proportion of proteins predicted to be secreted (79 %). Conclusion: The protocol described in this paper constitutes the first method to analyse proteins strongly bound to cell walls in grape skins. However, this method excludes the identification of labile proteins or proteins weakly bound to the cell wall. Significance and impact of the study: This protocol can be used for studying the role that strongly bound cell wall proteins play in development and defense processes in grape skins.
Esca is one of the major diseases affecting vineyards with direct impact on product yield; nevertheless, scientific studies concerning its impact on grape quality are scarce. As an attempt to better ...understand the mechanisms behind “Esca proper” development in grapes, this work focused on the identification of proteins whose expression is altered by the disease. 2‐DEs were performed on protein extracts from grape skins at different stages of maturity for two consecutive vintages. Grapes were collected in 2009 and in 2010 from plants that did not present signs of infection by Esca proper since the 2004 vintage and from plants that presented cast leaf symptoms at least once since 2004. For the first time, 13 proteins were shown to be influenced by Esca proper during the ripening process. Extensive bioinformatics analysis allowed the grouping of proteins involved in (i) stress tolerance and defense response, (ii) oxidative phosphorylation, (iii) oxidation–reduction processes in mitochondria, and (iv) oxidation–reduction processes in chloroplasts. Of these 13 proteins, cysteine synthase is the only one implicated in a metabolic pathway of oenological interest. This study shows how foliar symptoms of Esca proper may impact stress‐related pathways in grapes, which are characterized by modifications in the chain of oxidative phosphorylation and redox scavenging.
Aims: β-1,3-glucanase is one of the main pathogenesis related proteins of plants, involved in plant-pathogen interactions. Its effect on fungal pathogens is not entirely known. The hyphae of Botrytis ...cinerea are covered by an extra cellular matrix, mainly composed of a β-1,3-D-glucan. This matrix also contains a variety of enzymes, lipids and melanin which may play a role in fungal virulence. Methods and results: Cultures of Botrytis cinerea are made in presence of β-1,3-glucanase. The structure of the mycelium of Botrytis cinerea after exposure to β-1,3-glucanase during growth was examined by staining with Schiff's reagent and using the electron microscope. Without glucanase, hyphae have a normal diameter and were surrounded by a glucan matrix. Cytoplasm is dense and contains little vacuoles. The glucanase treatment removed most of the glucan sheath, but did not kill the fungus. The structure of the hyphae was changed by the treatment and their diameter increased. Membrane structure showed marked changes, the cytoplasm of the cells was less dense, but more inclusions were observed, including an increase in what appeared to be lipids. Conclusion: The appearance of the mycelium, whose glucan sheath has been removed, was that of cells under stress. The possible implications of the function of the glucan sheath during the interaction of Botrytis cinerea with its host during pathogenesis are discussed. Significance and impact of study: These changes following glucanase treatment would lead to a fungal mycelium which will be more sensitive to antifungal agents and might suggest ways of combating Botrytis infections by preventing the formation of the extra-cellular matrix.
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