Comparative proteomic analysis on fruit ripening processes in two varieties of tropical mango (Mangifera indica)

Mango (Mangifera indica L.) is an economically important fruit. However, the marketability of mango is affected by the perishable nature and short shelf-life of the fruit. Therefore, a better understanding of the mango ripening process is of great importance towards extending its postharvest shelf life. Proteomics is a powerful tool that can be used to elucidate the complex ripening process at the cellular and molecular levels. This study utilized 2-dimensional gel electrophoresis (2D-GE) coupled with MALDI-TOF/TOF to identify differentially abundant proteins during the ripening process of the two varieties of tropical mango, Mangifera indica cv. ‘Chokanan’ and Mangifera indica cv ‘Golden Phoenix’. The comparative analysis between the ripe and unripe stages of mango fruit mesocarp revealed that the differentially abundant proteins identified could be grouped into the three categories namely, ethylene synthesis and aromatic volatiles, cell wall degradation and stress-response proteins. There was an additional category for differential proteins identified from the ‘Chokanan’ variety namely, energy and carbohydrate metabolism. However, of all the differential proteins identified, only methionine gamma-lyase was found in both ‘Chokanan’ and ‘Golden Phoenix’ varieties. Six differential proteins were selected from each variety for validation by analysing their respective transcript expression using reverse transcription-quantitative PCR (RT-qPCR). The results revealed that two genes namely, glutathione S-transferase (GST) and alpha-1,4 glucan phosphorylase (AGP) were found to express in concordant with protein abundant. The findings will provide an insight into the fruit ripening process of different varieties of mango fruits, which is important for postharvest management

Sulfur metabolism in microalgae

La concentrazione media di SO4 2- in oceano è 28-30 mmol L-1. Essa ha subito notevoli variazioni nel corso della storia della Terra e potrebbe aver facilitato la radiazione delle alghe della linea rossa (alghe con chl a+c quali diatomee, dinoflagellate e coccolitoforidi) a discapito di quelle della linea verde (alghe con chl a+b) e dei cianobatteri. È ancora da chiarire se gli enzimi responsabili dell’assimilazione del SO4 2- negli organismi fotosintetici abbiano svolto un ruolo nel controllare l’adattamento delle alghe alle variazioni di concentrazione del SO4 2-. In accordo con studi precedenti, la mia tesi dimostra che diverse specie algali possono acclimatarsi/adattarsi a diverse concentrazioni di SO4 2-. Anche se la disponibilità di SO4 2- non ha provocato cambiamenti drastici nella composizione cellulare, l’attività degli enzimi coinvolti nell’assimilazione riduttiva del SO4 2- è stata sensibilmente modificata, soprattutto quella dell’ATP solforilasi (ATPS), suggerendo che la disponibilità di SO4 2- sia un fattore importante nel controllo delle risposte intracellulari a breve termine mediate da induzione/inibizione delle attività enzimatiche. Lo studio delle sequenze di ATPS ha rivelato che contrariamente ad altri organismi, quelle algali hanno molti residui di cisteina. La posizione di alcuni di essi è conservata, sebbene vi sia una notevole differenza tra alghe eucariotiche e α-cianobatteri, e β-cianobatteri. Per verificare se l’ATPS potesse essere redox regolata in modo diverso in questi gruppi, l’attività dell’ATPS di sette specie è stata testata dopo trattamento con agenti riducenti (ditiotreitolo) o ossidanti (trans-4,5- diidrossi-1,2-ditiano) dei gruppi tiolici delle cisteine. Le cisteine dell’ATPS parzialmente purificata da Synechocystis sp. (β-cianobatteri) e T. pseudonana (eucarioti/α-cianobatteri) sono state poi identificate mediante spettrometria di massa dopo alchilazione dei gruppi sulfidrilici con iodoacetamide. I risultati mostrano che il numero e la posizione delle cisteine nelle ATPS algali sono fattori importanti per la regolazione della loro attività.At present, the mean oceanic SO4 2- concentration is 28-30 mmol L-1. This nutrient underwent large variations during Earth history and may have influenced phytoplankton radiation by facilitating the expansion of algae of the red lineage (chl a+c algae like diatoms, dinoflagellates and coccolithophorids) at the expense of algae of the green algae (chl a+b algae) and cyanobacteria. Whether the enzymes that control SO4 2- assimilation in photosynthetic organisms have played a role in controlling algal adaptation to changes in SO4 2- concentration is however unclear. In agreement with previous studies, my thesis reveals that different algal species can modify their physiology to acclimate/adapt to different SO4 2- concentrations. Although SO4 2- availability did not elicit dramatic changes of cell internal composition, the activity of the enzymes involved in the reductive SO4 2- assimilation were appreciably modified, especially ATP sulfurylase (ATPS), suggesting that SO4 2- availability is an important factor in controlling short-term intracellular responses mediated by induction/inhibition of S-related enzymes. The study of ATPS sequences revealed that contrary to other organisms, algal ATPS has a high number of cysteine residues (cys). The position of some of these is conserved, but a notable difference exists between eukaryotic algae and α-cyanobacteria, and β-cyanobacteria. To test if ATPS may be redox regulated in different way in these groups, ATPS activity from seven species was tested after treatment with reducing (dithiothreitol) or oxidizing (trans-4,5-dihydroxy-1,2- dithiane) agents reacting with cys thiol groups. The cys of the partially purified ATPS from Synechocystis sp. (β-cyanobacteria) and T. pseudonana (eukaryotic/α-cyanobacteria) were then identified by mass spectrometry after sulfhydryl alkylation with 2-iodoacetamide. The results show that the number and position of cys in algal ATPS are important factors for the regulation of its activity

Analysis of the West African Power Pool (WAPP) and its development potential

First of all, it is necessary to specify that this study is an academic work carried out by a student. The hypothesis and the line of reasoning that aect the results obtained are proposed in the context of a master thesis. Electricity supply is a big challenge for West Africa. Indeed, the state members of the Economic Community of West African States (ECOWAS) face many problem of electricity as their production and distribution systems are not enough developed and reliable. A good and reliable electricity supply could allow to develop the industries and improve the attractiveness of the region. The purpose of the West African Power Pool (WAPP) is to develop the electricity sector in West Africa and guarantee a reliable and continuous electricity supply at a competitive cost. Creating an open market for the whole region seems to be the best strategy to achieve these goals. This kind of market could decrease the electricity price by the wholesale purchase of energy, a better resources management and the building of large centralized power plants. Investors can be attracted to invest in new power plants and develop the sector. The objective of the study is to analyze the benets of dierent electricity supply strategies for each country. An autarkic strategy for which each country use its local plants to produce electricity. An open market strategy for which the region is considered as a unique area with an open market.A part of independence strategy for which an open market is in place but the importing countries should produce a certain part of their electricity locally. Moreover a strategy introducing renewables technologies is assessed to evaluate the economical impact on an open market of these technologies. To evaluate these strategies, the expansion of the power pool is planned and evaluate on an economical point of view. The existing power pool is consider and candidate plants are added depending on the strategy and the country. In West Africa, the mainly used plants are thermal plants using natural gas, heavy fuel or diesel and some hydroelectric plants. The expansion is optimized using the software PLANELEC by the minimization of the net present cost (NPC). The economical evaluation is made on the NPC and the levelized cost of electricity (LCOE). The results demonstrate that the open market strategy provides the lowest LCOE. So all the countries will benet the creation of a market. The most used technology are combined cycle power plants and gas turbines using natural gas as a fuel. The renewable energy strategy will slightly increase the LCOE of the open market as these technologies are more expensive

Carbon Fixation in the Chemolithoautotrophic Bacterium Aquifex aeolicus Involves Two Low-Potential Ferredoxins as Partners of the PFOR and OGOR Enzymes

Aquifex aeolicus is a microaerophilic hydrogen- and sulfur -oxidizing bacterium that assimilates CO2 via the reverse tricarboxylic acid cycle (rTCA). Key enzymes of this pathway are pyruvate:ferredoxin oxidoreductase (PFOR) and 2-oxoglutarate:ferredoxin oxidoreductase (OGOR), which are responsible, respectively, for the reductive carboxylation of acetyl-CoA to pyruvate and of succinyl-CoA to 2-oxoglutarate, two energetically unfavorable reactions that require a strong reduction potential. We have confirmed, by biochemistry and proteomics, that A. aeolicus possesses a pentameric version of these enzyme complexes ((αβγδε)2) and that they are highly abundant in the cell. In addition, we have purified and characterized, from the soluble fraction of A. aeolicus, two low redox potential and oxygen-stable [4Fe-4S] ferredoxins (Fd6 and Fd7, E0 = −440 and −460 mV, respectively) and shown that they can physically interact and exchange electrons with both PFOR and OGOR, suggesting that they could be the physiological electron donors of the system in vivo. Shotgun proteomics indicated that all the enzymes assumed to be involved in the rTCA cycle are produced in the A. aeolicus cells. A number of additional enzymes, previously suggested to be part of a putative partial Wood-Ljungdahl pathway used for the synthesis of serine and glycine from CO2 were identified by mass spectrometry, but their abundance in the cell seems to be much lower than that of the rTCA cycle. Their possible involvement in carbon assimilation is discussed

Direct and indirect influence of sulfur availability on phytoplankton evolutionary trajectories

The sulfate facilitation hypothesis suggests that changes in ocean sulfate concentration influenced the rise to dominance of phytoplankton species of the red lineage. The mechanistic reasons for this phenomenon are not yet understood. We started to address this question by investigating the differences in S utilization by algae of the green and red lineages and in cyanobacteria cultured in the presence of either 5 mmol L-1 (approximately equivalent to Paleozoic ocean concentrations) or 30 mmol L- 1 (corresponding to post-Mesozoic/ extant concentrations) sulfate. The activities of the main enzymes involved in SO42-- assimilation changed in response to changes in growth sulfate concentration. ATP sulfurylase showed different kinetics in the various taxa, with an especially odd behavior for the dinoflagellate. Sulfate availability had a modest effect on cell organic composition. Species-specific differences in the use of some elements were instead obvious in algae grown in the presence of different sulfate concentrations, overall confirming that algae of the red lineage do better at high sulfate than algae of the green lineage. The increase in sulfate concentration may thus have had an impact on phytoplankton radiation both through changes in their enzymatic machinery and through indirect repercussion on elemental usage

Sulphur and algae: metabolism, ecology and evolution.

Sulphur is one of the main components of algal cells, with a cell quota typically very similar to that of phosphorus. S is present in numerous pivotal structural and functional compounds such as the amino acids cysteine and methionine, non-protein thiols (glutathione), sulpholipids, vitamins and cofactors, cell wall constituents. Sulphur is also a constituent of dimethylsulphoniopropionate (DMSP), which in some algae can represent a very large portion of cell S and is involved in algal responses to a variety of abiotic and biotic stresses, in addition to being indicted (controversially) of an important role in climate control. Algae acquire S as sulphate (SO42-), the most abundant form of inorganic S in nature. Sulphur is however assimilated in the organic matter as sulphide (S2-). A non-trivial amount of reducing power is thus required for S assimilation. In both algae and plants, S assimilation mostly takes place in the chloroplast. In eukaryotic algae (except dinoflagellates) and oceanic cyanobacteria the first step in sulphate assimilation, catalysed by ATP sulfurylase (ATPS) is subject to redox regulation, whereas in vascular plants APS reductase is the main control point in the pathway. This chapter describes in details the sulphate reduction and sulphation pathways. Attention is also given to the synthesis of glutathione and phytochelatins from cysteine and to the production of DMSP from methionine. The interactions among S assimilation and C, N and P metabolism are also addressed. Current hypotheses on the role of spatial and temporal changes of S availability on algae evolutionary trajectories are discussed

Visual-Thermal comfort evaluation and comparison: application to an open-space office

The research investigates how different design elements of a building façade affect the conditions inside of it, and so the users’ comfort. The aim of the project is to observe how we can respect the comfort of the user in terms of visual and thermal comfort

Redox regulation of ATP sulfurylase activity in microalgae.

ATP sulfurylase (ATPS) catalyzes the first step of sulfur assimilation in photosynthetic organisms. An ATPS type A is mostly present in freshwater cyanobacteria, with four conserved cysteine residues. Oceanic cyanobacteria and most eukaryotic algae instead, possess an ATPS-B containing seven to ten cysteines; five of them are conserved, but only one in the same position as ATPS-A. We investigated the role of cysteines on the regulation of the different algal enzymes.We found that the activity of ATPS-B from four different microorganisms was enhanced when reduced and decreased when oxidized. The LC-MS/MS analysis of the ATPS-B from the marine diatom Thalassiosira pseudonana showed that the residue Cys- 247 was presumably involved in the redox regulation. The absence of this residue in the ATPS-A of the freshwater cyanobacterium Synechocystis sp. instead, was consistent with its lack of regulation. Some other conserved cysteine residues in the ATPS from T. pseduonana and not in Synechocystis sp.were accessible to redox agents and possibly play a role in the enzyme regulation. Furthermore, the fact that oceanic cyanobacteria have ATPS-B structurally and functionally closer to that from most of eukaryotic algae than to the ATPS-A from other cyanobacteria suggests that life in the sea or freshwater may have driven the evolution of ATPS

Diversity and regulation of ATP sulfurylase in photosynthetic organisms

ATP sulfurylase (ATPS) catalyzes the first committed step in the sulfate assimilation pathway, the activation of sulfate prior to its reduction. ATPS has been studied in only a few model organisms and even in these cases to a much smaller extent than the sulfate reduction and cysteine synthesis enzymes. This is possibly because the latter were considered of greater regulatory importance for sulfate assimilation. Recent evidences (reported in this paper) challenge this view and suggest that ATPS may have a crucial regulatory role in sulfate assimilation, at least in algae. In the ensuing text, we summarize the current knowledge on ATPS, with special attention to the processes that control its activity and gene(s) expression in algae. Special attention is given to algae ATPS proteins. The focus on algae is the consequence of the fact that a comprehensive investigation of ATPS revealed that the algal enzymes, especially those that are most likely involved in the pathway of sulfate reduction to cysteine, possess features that are not present in other organisms. Remarkably, algal ATPS proteins show a great diversity of isoforms and a high content of cysteine residues, whose positions are often conserved. According to the occurrence of cysteine residues, the ATPS of eukaryotic algae is closer to that of marine cyanobacteria of the genera Synechococcus and Prochlorococcus and is more distant from that of freshwater cyanobacteria. These characteristics might have evolved in parallel with the radiation of algae in the oceans and the increase of sulfate concentration in seawater

Diversity of CO2-concentrating mechanisms and responses to CO2 concentration in marine and freshwater diatoms

The presence of CO2-concentrating mechanisms (CCMs) is believed to be one of the characteristics that allows diatoms to thrive in many environments and to be major contributors to global productivity. Here, the type of CCM and the responses to variable CO2 concentration were studied in marine and freshwater diatoms. At 400 ppm, there was a large diversity in physiological and biochemical mechanisms among the species. While Phaeodactylum tricornutum mainly used HCO3–, Thalassiosira pseudonana mainly used CO2. Carbonic anhydrase was an important component of the CCM in all species and C4 metabolism was absent, even with T. weissflogii. For all species, at 20 000 ppm, the affinity for dissolved inorganic carbon was lower than at 400 ppm CO2 and the reliance on CO2 was higher. Despite the difference in availability of inorganic carbon in marine and fresh waters, there were only small differences in CCMs between species from the two environments, and Navicula pelliculosa behaved similarly when grown in the two environments. The results suggest that species-specific differences are great, and more important than environmental differences in determining the nature and effectiveness of the CCM in diatoms