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

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

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