For these reasons, marine organisms may represent precious resources for developing drug candidates, cosmetics, nutritional supplements, and molecular probes for improving our well-being.
Thus, these substances often possess meaningful pharmacological properties.
Many of these chemicals affect metabolic pathways that are common to humans and are involved in critical physiological functions. Since then, these organisms have dealt successfully with competitors and predators by developing a unique arsenal of highly effective secondary metabolites for their defense, reproduction, and communication. The majority of marine organisms has an evolutionary history that dates back to the Cambrian, some 500 million years ago.
More recently, the amazing biodiversity represented by the world's oceans have been realized to represent an equally and exceptionally rich source of valuable bioactive compounds. This has led to the development of life-saving drugs for treating a multitude of conditions including infectious, cardiovascular, malignant, and diabetic disease. This epistatic relationship between PPDK and O2 is further supported by quantitative and association genetics.Man has probably used since his existence plants and plant-derived compounds for his health care and well-being. The direct effect of O2 on PPDK gene expression provides a clue for explaining the competition between C and N metabolisms. It is substantiated by the data on the Opaque-2 gene encoding a transcription factor with pleiotropic effect affecting lysine content and carbohydrate metabolism, thus acting indirectly on starch/amino acid ratio. This hypothesis is based on biochemical arguments involving the negative effect of PPi on the ADP-glucose pyrophosphorylase (Agpase), a key-enzyme of starch synthesis, and the role of phosphoenolpyruvate (PEP) in aromatic amino acid synthesis. Detailed proteomic analysis of metabolism shows an upsurge of the pyruvate-Pi-dikinase (PPDK) in the late filing period (21 DAP onwards) that is interpreted as a switch in the starch/protein balance. Although the expression of enzymes involved in storage product synthesis is dominant in the accumulation phase, the proportion of protein destination and protein synthesis gene products is still important. A major change occurred at the transition from lag phase where final grain size is established to grain filling where starch and protein are accumulated in the endosperm storage tissue. It allowed identifying genes expressed at each developmental stage and the shift occurring from one stage to the other. The specific late-stage accumulation of the pyruvate orthophosphate dikinase may suggest a critical role of this enzyme in the starch-protein balance through inorganic pyrophosphate-dependent restriction of ADP-glucose synthesis in addition to its usually reported influence on the alanine-aromatic amino acid synthesis balance.Ī combined transcriptomic, proteomic and metabolic analysis provided an overview of the main changes occurring in gene expression during maize kernel development. A relative increase of abundance of the glycolytic enzymes compared to tricarboxylic acid enzymes is consistent with the recent demonstration of anoxic conditions during starch accumulation in the endosperm. An important protein turnover, which is likely associated with the switch from growth and differentiation to storage, was also suggested from the high amount of proteases. Early stages, devoted to cellularization, cell division, and cell wall deposition, corresponded to maximal expression of actin, tubulins, and cell organization proteins, of respiration metabolism (glycolysis and tricarboxylic acid cycle), and of protection against reactive oxygen species. Comprehensive investigation of the functions associated with clusters resulted in a consistent picture of the developmental coordination of cellular processes. Hierarchical clustering analysis allowed four main developmental profiles to be recognized. The accumulation pattern of 409 proteins at seven developmental stages was examined. Here, we present a proteomic study of maize endosperm development. Although the morphological steps of maize (Zea mays) endosperm development are well described, very little is known concerning the coordinated accumulation of the numerous proteins involved.
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