The Skeletal Organic Matrix from Mediterranean Coral Balanophyllia europaea Influences Calcium Carbonate Precipitation

Scleractinian coral skeletons are made mainly of calcium carbonate in the form of aragonite. The mineral deposition occurs in a biological confined environment, but it is still a theme of discussion to what extent the calcification occurs under biological or environmental control. Hence, the shape, size and organization of skeletal crystals from the cellular level through the colony architecture, were attributed to factors as diverse as mineral supersaturation levels and organic mediation of crystal growth. The skeleton contains an intra-skeletal organic matrix (OM) of which only the water soluble component was chemically and physically characterized. In this work that OM from the skeleton of the Balanophyllia europaea, a solitary scleractinian coral endemic to the Mediterranean Sea, is studied in vitro with the aim of understanding its role in the mineralization of calcium carbonate. Mineralization of calcium carbonate was conducted by overgrowth experiments on coral skeleton and in calcium chloride solutions containing different ratios of water soluble and/or insoluble OM and of magnesium ions. The precipitates were characterized by diffractometric, spectroscopic and microscopic techniques. The results showed that both soluble and insoluble OM components influence calcium carbonate precipitation and that the effect is enhanced by their co-presence. The role of magnesium ions is also affected by the presence of the OM components. Thus, in vitro, OM influences calcium carbonate crystal morphology, aggregation and polymorphism as a function of its composition and of the content of magnesium ions in the precipitation media. This research, although does not resolve the controversy between environmental or biological control on the deposition of calcium carbonate in corals, sheds a light on the role of OM, which appears mediated by the presence of magnesium ions

Identification of NAD(P)H Quinone Oxidoreductase Activity in Azoreductases from P. aeruginosa: Azoreductases and NAD(P)H Quinone Oxidoreductases Belong to the Same FMN-Dependent Superfamily of Enzymes

Water soluble quinones are a group of cytotoxic anti-bacterial compounds that are secreted by many species of plants, invertebrates, fungi and bacteria. Studies in a number of species have shown the importance of quinones in response to pathogenic bacteria of the genus Pseudomonas. Two electron reduction is an important mechanism of quinone detoxification as it generates the less toxic quinol. In most organisms this reaction is carried out by a group of flavoenzymes known as NAD(P)H quinone oxidoreductases. Azoreductases have previously been separate from this group, however using azoreductases from Pseudomonas aeruginosa we show that they can rapidly reduce quinones. Azoreductases from the same organism are also shown to have distinct substrate specificity profiles allowing them to reduce a wide range of quinones. The azoreductase family is also shown to be more extensive than originally thought, due to the large sequence divergence amongst its members. As both NAD(P)H quinone oxidoreductases and azoreductases have related reaction mechanisms it is proposed that they form an enzyme superfamily. The ubiquitous and diverse nature of azoreductases alongside their broad substrate specificity, indicates they play a wide role in cellular survival under adverse conditions

Sucrose and Starch Metabolism

International audienceThe metabolism of starch and sucrose fuels all aspects of plant growth and development. Over the last decade, significant advances have been made in our understanding of the metabolism of these compounds through the use of model systems, mainly Arabidopsis. Legume species are characterised by their capacity to form symbioses with Rhizobium, a nitrogen-fixing bacterium, leading to up to half the carbon assimilated in photosynthesis being sequestered to their roots. Study of a legume model may therefore increase our knowledge about carbohydrate turnover. We review here the resources available and the contribution that research on Lotus japonicus has made to our knowledge of sucrose breakdown and starch metabolism in relation to plant growth and development processes, especially processes that are legume specific

From Arabidopsis to Crops: The Arabidopsis QQS Orphan Gene Modulates Nitrogen Allocation Across Species

To improve the nitrogen use efficiency (NUE) of crops to increase yields, one approach is to develop crops with improved NUE. Qua Quine Starch (QQS), a species-specific orphan gene present only in Arabidopsis thaliana, has a novel, unexpected functionality. Approximately 0.5- 8% of genes in a given species are uniquely present in that species, having no homologs in other species. They represent a significant fraction of eukaryotic and prokaryotic genomes, and are thought to be a determinant of the character of a species. However, little is known about the functional significance of these so-called species-specific or orphan genes. QQS can affect the extremely important trait of protein content when expressed in other species, in soybean, maize and rice. Understanding QQS functions has multiple impacts, revealing how plants partition precious carbon and nitrogen resources. Here, we report QQS interactor nuclear factor Y subunit C4 (NF-YC4), affects carbon and nitrogen allocation to protein in soybean and maize. QQS and its related network may be used as a tool to increase the protein content in crops, and to study the 2 nitrogen allocation network. RNA-Sequencing analyses of the QQS mutant materials have identified candidate genes involved in regulation of nitrogen allocation.This is a manuscript of a chapter published as O’Conner S. et al. (2018) From Arabidopsis to Crops: The Arabidopsis QQS Orphan Gene Modulates Nitrogen Allocation Across Species. In: Shrawat A., Zayed A., Lightfoot D. (eds) Engineering Nitrogen Utilization in Crop Plants. Springer, Cham. doi: 10.1007/978-3-319-92958-3_6. Posted with permission.</p

On the Elaborate Network of Thioredoxins in Higher Plants

International audienc