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Galactone-γ-lactone-dependent ascorbate biosynthesis alters wheat kernel maturation

Kernel development and maturation involve several well-characterised events, such as changes in ascorbate (ASC) metabolism, protein synthesis and storage, programmed cell death (PCD) of starchy endosperm and tissue dehydration. Despite many studies focusing on these events, whether and how they are metabolically related to each other, remains to be elucidated. In the present investigation, the changes in ASC-related metabolism, PCD occurrence, kernel filling and dehydration have been analysed during kernel maturation, over a 3-year period in plants grown under normal conditions and in plants displaying modified ASC synthesis. The obtained results suggest that ASC plays a pivotal role in the network of events characterising kernel maturation. During this process, a decrease in ASC content occurs. When ASC biosynthesis is improved in the kernel, by feeding the plants with its immediate precursor, L-galactone-γ-lactone (GL), the decrease in ASC, observed during kernel maturation, is delayed. As a consequence, ascorbate peroxidase (APX) activity is also enhanced. Moreover, a delay in the ASC decrease permits a delay in PCD occurring in kernel storage tissues and in kernel dehydration. Interestingly, the data emerging from the present investigation suggest that the delay in the decrease in ASC content and APX activity also improves kernel filling. The relevance of the ascorbate-dependent redox regulation for kernel productivity is discussed.

Over-expression of Trxo1 increases the viability of tobacco BY-2 cells under H2O2 treatment

BACKGROUND AND AIMSnReactive oxygen species (ROS), especially hydrogen peroxide, play a critical role in the regulation of plant development and in the induction of plant defence responses during stress adaptation, as well as in plant cell death. The antioxidant system is responsible for controlling ROS levels in these processes but redox homeostasis is also a key factor in plant cell metabolism under normal and stress situations. Thioredoxins (Trxs) are ubiquitous small proteins found in different cell compartments, including mitochondria and nuclei (Trxo1), and are involved in the regulation of target proteins through reduction of disulphide bonds, although their role under oxidative stress has been less well studied. This study describes over-expression of a Trxo1 for the first time, using a cell-culture model subjected to an oxidative treatment provoked by H2O2.nnnMETHODSnControl and over-expressing PsTrxo1 tobacco (Nicotiana tabacum) BY-2 cells were treated with 35u2009mm H2O2 and the effects were analysed by studying the growth dynamics of the cultures together with oxidative stress parameters, as well as several components of the antioxidant systems involved in the metabolism of H2O2. Analysis of different hallmarks of programmed cell death was also carried out.nnnKEY RESULTSnOver-expression of PsTrxo1 caused significant differences in the response of TBY-2 cells to high concentrations of H2O2, namely higher and maintained viability in over-expressing cells, whilst the control line presented a severe decrease in viability and marked indications of oxidative stress, with generalized cell death after 3u2009d of treatment. In over-expressing cells, an increase in catalase activity, decreases in H2O2 and nitric oxide contents and maintenance of the glutathione redox state were observed.nnnCONCLUSIONSnA decreased content of endogenous H2O2 may be responsible in part for the delayed cell death found in over-expressing cells, in which changes in oxidative parameters and antioxidants were less extended after the oxidative treatment. It is concluded that PsTrxo1 transformation protects TBY-2 cells from exogenous H2O2, thus increasing their viability via a process in which not only antioxidants but also Trxo1 seem to be involved.

Plant Cell Cultures as Model Systems to Study Programmed Cell Death

The study of programmed cell death (PCD) activated in a certain group of cells is complex when analyzed in the whole plant. Plant cell suspension cultures are useful when investigating PCD triggered by environmental and developmental stimuli. Due to their homogeneity and the possibility to synchronize their responses induced by external stimuli, these cultures are used for studying the signaling pathways leading to PCD. The first problem in the analysis of PCD in cell cultures is the quantification of cell viability/death over time. Cultured cells from different plant species may have specific mitotic patterns leading to calli or cell chains mixed to single cell suspensions. For this reason, not all cell cultures allow morphological parameters to be investigated using microscopy analysis, and adapted or ad hoc methods are needed to test cell viability.Here we report on some accurate methods to establish and propagate cell cultures from different plant species, including crops, as well as to determine cell viability and PCD morphological and genetic markers. In particular, we describe a protocol for extracting nucleic acids required for real-time PCR analysis which has been optimized for those cell cultures that do not allow the use of commercial kits.

Effects of ionizing radiation on bio-active plant extracts useful for preventing oxidative damages

Abstract Humans are exposed to ionizing radiations in medical radiodiagnosis and radiotherapy that cause oxidative damages and degenerative diseases. Airplane pilots, and even more astronauts, are exposed to a variety of potentially harmful factors, including cosmic radiations. Among the phytochemicals, phenols are particularly efficient in countering the oxidative stress. In the present study, different extracts obtained from plant food, plant by-products and dietary supplements, have been compared for their antioxidant properties before and after irradiation of 140 cGy, a dose absorbed during a hypothetical stay of three years in the space. All the dry extracts, characterized in terms of vitamin C and phenolic content, remained chemically unaltered and maintained their antioxidant capability after irradiation. Our results suggest the potential use of these extracts as nutraceuticals to protect humans from oxidative damages, even when these extracts must be stored in an environment exposed to cosmic radiations as in a space station.

Plant Programmed Cell Death

Programmed cell death (PCD) is a controlled mechanism that eliminates specific cells under developmental or environmental stimuli. All organisms—from bacteria to multicellular eukaryotes—have the ability to induce PCD in selected cells. Although this process was first identified in plants, the interest in deciphering the signaling pathways leading to PCD strongly increased when evidence came to light that PCD may be involved in several human diseases. In plants, PCD activation ensures the correct occurrence of growth and developmental processes, among which embryogenesis and differentiation of tracheary elements. PCD is also part of the defense responses activated by plants against environmental stresses, both abiotic and biotic. This chapter gives an overview of the roles of PCD in plants as well as the problems arising in classifying different kinds of PCD according to defined biochemical and cellular markers, and in comparison with the various types of PCD occurring in mammal cells. The importance of understanding PCD signaling pathways, with their elicitors and effectors, in order to improve plant productivity and resistance to environmental stresses is also taken into consideration.

Glutathione as a Key Player in Plant Abiotic Stress Responses and Tolerance

Adverse environmental conditions, such as drought, salinity, high temperature, and toxic metal accumulation, affect plant growth and fitness. Plants have evolved a number of interconnected molecular pathways to defend themselves against different abiotic stresses. In these metabolic networks, redox signaling plays a pivotal role in determining plant tolerance to stress and survival. Glutathione/glutathione disulfide is one of the most versatile redox couples in metabolism. It directly or indirectly buffers the cellular redox state, by acting as enzyme cofactor, controlling the oxido-reduction of other thiols and participating in post-translational protein modifications under both physiological and stress conditions. Glutathione also plays a key role as a conjugating agent in detoxification against xenobiotics or metabolites which need to be sequestered within the vacuole. Glutathione also acts as a signal controlling gene expression and cell cycle progression. These features highlight the importance of glutathione in regulating plant growth and development as well as in conferring tolerance to plants subjected to stress. This chapter describes the involvement of this multifaceted molecule in plant abiotic stress responses.

Multidimensional Approach to Solanaceae’s Nutritional and Gustative Aspects

An innovative approach based on a potentiometric sensor has been employed for peppers characterization. Despite a great number of hot pepper varieties are cultivated worldwide and are consumed, a simple method to discriminate them does not exist yet. A multidimensional system centered on a liquid sensor was used to successfully characterize five different pepper species by means of an easy and rapid procedure. The information deriving from cyclic voltammetry analyses was acquired by the electronic system and further evaluated through a multivariate data analysis approach. The calculated models showed an efficiency of 100 % in the classification of the hot peppers and were able to predict with good accuracy the antioxidant content of the pepper exemplars.

P.06.22 ANTIOXIDANT ACTIVITY OF INULIN AND ITS ABILITY TO PREVENT HUMAN COLONIC MUSCLE CELL IMPAIRMENT INDUCED BY LIPOPOLYSACCHARIDE MUCOSAL EXPOSURE

s of the 19th National Congress of Digestive Diseases / Digestive and Liver Disease 45S (2013) S55–S218 S133 1.13–2.25, p<0.025), whereas ERD had a slight relationship with IBS (ERD: OR=1.22, 95% CI: 0.80–1.87, p=ns). Conclusions: These results show an overlapping of GERD in a 45% of IBS pts (n=144/321). A common functional starting problem could explain this association, as well as the improvement of IBS-like symptoms in patients with reflux disease receiving anti-reflux treatment, as confirmed by studies. Further studies looking at all the putative variables involved in symptom perception and response to therapy are needed in these subgroups of patients.