Cell wall modifications during fruit ripening: when a fruit is not the fruit

Textural changes that lead to softening of fruits are accompanied by loss of neutral sugars, solubilisation and depolymerisation of the polysaccharides of the cell wall, and rearrangements of their associations, as the result of the combined action of several cell wall-modifying enzymes, acting in both pectic and hemicellulosic fractions. Recent studies on the structure of the plant cell wall have disclosed a large number and type of biochemical linkages between the components. Such linkages are potential targets for enzymatic action and draw attention to the putative involvement of several members of enzymes able to act and modify its structure in a developmental and coordinated way. Extensive work on fruit ripening has been done using tomato (Solanum lycopersicum [Lycopersicon esculentum Mill.]) as a plant model and the information concerning fruits other than model species is fragmented and incomplete. However, recent data from the literature had disclosed that differences exist between fruits, and even between cultivars of the same fruit species. These differences exist in the type and extent of the modification of the polysaccharides of the cell wall and in the expression and regulation of cell wall-modifying enzymes. In addition, genetic manipulation of cell wall-modifying genes re-opened the discussion about the real effect of these enzymes in the cell wall and their role in fruit softening. Moreover, the function of each enzyme has been proposed based on its homology with other annotated sequences, but, in most cases, confirmation of activity in planta and substrate specificity remains to be investigated. This aspect and recognized limitations of the in vitro enzymatic activity assays also need to be considered when discussing their role. This paper provides a critical review on the current knowledge concerning these differences and emphasises the need of using other species and more accurate methodologies to investigate general mechanisms and fruit specificities of softening among different fleshy fruits

How to survive earthquakes: the example of Norcia

Trabalho apresentado em International Conference on Earthquake Engineering and Structural Dynamics, 12-14 June 2017, Reykyjavik, IcelandN/

Cloning, characterisation and expression analysis of cDNA clones encoding cell wall-modifying enzymes isolated from ripe apples

Fruit softening is accompanied by modifications of the cell wall pectic and hemicellulosic fractions, as the result of the combined action of several cell wall-modifying enzymes. The objective of this work was to clone specific cDNAs that encode isoforms of cell wall-modifying enzymes, which are expressed during the final stages of apple softening, and to establish a temporal sequence of their accumulation. A cDNA library enriched with mRNA isolated from over-ripe fruit was constructed and screened. A pectin methylesterase (MdPME1), a pectate lyase (MdPL1), an -l-arabinofuranosidase (MdAF1) an endo-1,4- -glucanase (MdEG1), two xyloglucan endotransglucosylase/hydrolases (Md-XTH1 and Md-XTH2), and an alpha-expansin (MdEXPA3) specific cDNAs were identified by homology-based cloning, and their mRNA accumulation was examined during fruit growth and ripening. The expression of an apple -galactosidase ( -Gal; pABG1) and a polygalacturonase (PG; pGDPG-1) mRNA previously reported was also investigated using the same biological material. Transcripts of all enzymes, except MdPME1, could be unambiguously detected by semi-quantitative RT-PCR in fruit during ripening. However, transcripts of MdEG1 were more abundant at fruit set and MdPL1 exhibited higher expression before commercial maturity. The strongest RT-PCR signals in over-ripe fruit were observed for PG, -Gal and Md-XTH1 clones. Two XTHs were detected in over-ripe fruit. While Md-XTH1 acts constitutively during fruit development, Md-XTH2 showed a ripening-related pattern. The Md-XTH2-encoded protein was heterologously expressed in Saccharomyces cerevisiae and showed both transglycosylase and hydrolase activities. Expression analyses conducted in flowers, peduncles, young and expanded leaves, and petioles of senescent leaves revealed that none of the cloned cDNAs is fruit specifi

Evidence for deuterium astration in the planetary nebula Sh2-216?

We present FUSE observations of the line of sight to WD0439+466 (LS V +46 21), the central star of the old planetary nebula Sh2-216. The FUSE data shows absorption by many interstellar and stellar lines, in particular D I, H2 (J = 0 - 9), HD (J = 0 - 1), and CO. Many other stellar and ISM lines are detected in the STIS E140M HST spectra of this sightline, which we use to determine N(HI). We derive, for the neutral gas, D/H=(0.76 +0.12 -0.11)E-5, O/H = (0.89 +0.15 -0.11)E-4 and N/H = (3.24 +0.61-0.55)E-5. We argue that most of the gas along this sightline is associated with the planetary nebula. The low D/H ratio is likely the result of this gas being processed through the star (astrated) but not mixed with the ISM. This would be the first time that the D/H ratio has been measured in predominantly astrated gas. The O/H and N/H ratios derived here are lower than typical values measured in other planetary nebulae likely due to unaccounted for ionization corrections.Comment: Accepted for publication is ApJ

Sequestração geológica de dióxido de carbono: notas sobre o estado-da-arte

Após uma breve introdução sobre os conceitos de (i) Alterações climáticas vs Alterações globais e de (ii) Gases de efeito de estufa, os autores apresentam o estado-da-arte sobre os principais problemas relacionados com a redução do dióxido de carbono e sua sequestração geológica. Por fim, fazem referência aos projectos existentes neste domínio no “Grupo de Investigação em Energia” do Centro de Investigação em Alterações Globais, Energia, Ambiente e Bioengenharia - CIAGEB da Universidade Fernando Pessoa. After a short introduction regarding concepts such as (i) Climate change vs Global changes, and (ii) Greenhouse gases effect, the authors present the state-of-the-art regarding problems related with Carbon dioxide abatement and geological sequestration. Finally, the authors refer to the current projects on this particular issue being developed by the “Energy Research Group” of the Global Change, Energy, Environment and Bioengineering RDID&D Unit – CIAGEB of Universidade Fernando Pessoa

Electrochemical evaluation of total antioxidant capacity of beverages using a purine-biosensor

In this paper, it was evaluated the total antioxidant capacity (TAC) of beverages using an electrochemical biosensor. The biosensor consisted on the purine base (guanine or adenine) electro-immobilization on a glassy carbon electrode surface (GCE). Purine base damage was induced by the hydroxyl radical generated by Fenton-type reaction. Five antioxidants were applied to counteract the deleterious effects of the hydroxyl radical. The antioxidants used were ascorbic acid, gallic acid, caffeic acid, coumaric acid and resveratrol. These antioxidants have the ability to scavenger the hydroxyl radical and protect the guanine and adenine immobilized on the GCE surface. The interaction carried out between the purinebase immobilized and the free radical in the absence and presence of antioxidants was evaluated by means of changes in the guanine and adenine anodic peak obtained by square wave voltammetry (SWV). The results demonstrated that the purine-biosensors are suitable for rapid assessment of TAC in beverages

Electrochemical DNA-sensor for evaluation of total antioxidant capacity of flavours and flavoured waters using superoxide radical damage

In this paper, a biosensor based on a glassy carbon electrode (GCE) was used for the evaluation of the total antioxidant capacity (TAC) of flavours and flavoured waters. This biosensor was constructed by immobilising purine bases, guanine and adenine, on a GCE. Square wave voltammetry (SWV) was selected for the development of this methodology. Damage caused by the reactive oxygen species (ROS), superoxide radical (O2·−), generated by the xanthine/xanthine oxidase (XOD) system on the DNA-biosensor was evaluated. DNA-biosensor encountered with oxidative lesion when it was in contact with the O2·−. There was less oxidative damage when reactive antioxidants were added. The antioxidants used in this work were ascorbic acid, gallic acid, caffeic acid, coumaric acid and resveratrol. These antioxidants are capable of scavenging the superoxide radical and therefore protect the purine bases immobilized on the GCE surface. The results demonstrated that the DNA-based biosensor is suitable for the rapid assess of TAC in beverages