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Although primarily studied in relation to photorespiration, serine metabolism in chloroplasts may play a key role in plant CO2 fertilization responses by linking CO2 assimilation with growth. Here, we show that the phosphorylated serine pathway is part of a 'photosynthetic C1 pathway' and demonstrate its high activity in foliage of a C3 tree where it rapidly integrates photosynthesis and C1 metabolism contributing to new biomass via methyl transfer reactions, imparting a large natural 13C-depleted signature. Using 13CO2-labelling, we show that leaf serine, the S-methyl group of leaf methionine, pectin methyl esters, and the associated methanol released during cell wall expansion during growth, are directly produced from photosynthetically-linked C1 metabolism, within minutes of light exposure. We speculate that the photosynthetic C1 pathway is highly conserved across the photosynthetic tree of life, is responsible for synthesis of the greenhouse gas methane, and may have evolved with oxygenic photosynthesis by providing a mechanism of directly linking carbon and ammonia assimilation with growth. Although the rise in atmospheric CO2 inhibits major metabolic pathways like photorespiration, our results suggest that the photosynthetic C1 pathway may accelerate and represents a missing link between enhanced photosynthesis and plant growth rates during CO2 fertilization under a changing climate. A photosynthetic C1 pathway starting with CO2 and NH3 assimilation and ending with methionine synthesis is highly active in foliage of a C3 tree, where it rapidly integrates photosynthesis and C1 metabolism contributing to new biomass via methyl transfer reactions. [ABSTRACT FROM AUTHOR]

Energy status and nutrients regulate photosynthetic protein expression. The unicellular green alga Chromochloris zofingiensis switches off photosynthesis in the presence of exogenous glucose (+Glc) in a process that depends on hexokinase (HXK1). Here, we show that this response requires that cells lack sufficient iron (−Fe). Cells grown in −Fe+Glc accumulate triacylglycerol (TAG) while losing photosynthesis and thylakoid membranes. However, cells with an iron supplement (+Fe+Glc) maintain photosynthesis and thylakoids while still accumulating TAG. Proteomic analysis shows that known photosynthetic proteins are most depleted in heterotrophy, alongside hundreds of uncharacterized, conserved proteins. Photosynthesis repression is associated with enzyme and transporter regulation that redirects iron resources to (a) respiratory instead of photosynthetic complexes and (b) a ferredoxin-dependent desaturase pathway supporting TAG accumulation rather than thylakoid lipid synthesis. Combining insights from diverse organisms from green algae to vascular plants, we show how iron and trophic constraints on metabolism aid gene discovery for photosynthesis and biofuel production. The cofactor iron is essential for cellular energy metabolism. Proteomics reveals how the interplay of iron limitation with glucose signaling underlies how a green alga turns off photosynthesis during lipid accumulation. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) using magnetically coupled resonators is being integrated into space vehicles destined for the lunar surface. The dusty soil on the Moon, called lunar regolith, is known to adhere to surfaces and is also known to contain iron, including iron oxides and metallic iron. Regolith samples are limited, and lunar soil simulants are commonly used in space science research for efforts in surface vehicle navigation, in-situ resource utilization, and power infrastructure. However, most simulants contain no metallic iron, and research involving electromagnetic field interactions with regolith would benefit from incorporating metallic iron into test samples. This work presents experimental results from tests using WPT with magnetically coupled resonators in the presence of various standard lunar simulants, plus a new iron-enriched simulant and metallic iron powders. Results for power transfer efficiency, thermal response, and frequency response are presented and demonstrate that the presence of metallic iron and its particle size are critical factors affecting the coupling of the incident magnetic field with lunar simulants and iron powder samples. The importance of particle size-to-skin depth ratio is discussed. Attenuation constants for various iron powders are estimated from experimental data and compared to those of lunar regolith and simulants. [ABSTRACT FROM AUTHOR]

Parental effects have been largely unexplored in marine organisms and may play a significant role in dictating the phenotypic range of traits in coral offspring, influencing their ability to survive environmental challenges. This study explored parental effects and life-stage differences in the Hawaiian reef-building coral Montipora capitata from different environments by examining the biochemical composition of mature coral colonies and their eggs. Our results indicate that there are large biochemical differences between adults and eggs, with the latter containing higher concentration of lipids (mostly wax esters), ubiquitinated proteins (which may indicate high turnover rate of proteins) and antioxidants (e.g., manganese superoxide dismutase). Adults displayed high phenotypic plasticity, with corals from a high-light environment having more wax esters, lighter tissue δC signatures and higher Symbiodinium densities than adults from the low-light environment who had higher content of accessory pigments. A green-algal pigment (α-carotene) and powerful antioxidant was present in eggs; it is unclear whether this pigment is acquired from heterotrophic food sources or from endolithic green algae living in the adult coral skeletons. Despite the broad phenotypic plasticity displayed by adults, parental investment in the context of provisioning of energy reserves and antioxidant defense was the same in eggs from the different sites. Such equality in investment maximizes the capacity of all embryos and larvae to cope with challenging conditions associated with floating at the surface and to disperse successfully until an appropriate habitat for settlement is found. [ABSTRACT FROM AUTHOR]

Global primary production is driven largely by oxygenic photosynthesis, with algae as major contributors. The green alga Chromochloris zofingiensis reversibly switches off photosynthesis in the presence of glucose in the light and augments production of biofuel precursors (triacylglycerols) and the high-value antioxidant astaxanthin. Here we used forward genetics to reveal that this photosynthetic and metabolic switch is mediated by the glycolytic enzyme hexokinase (CzHXK1). In contrast to wild-type, glucose-treated hxk1 mutants do not shut off photosynthesis or accumulate astaxanthin, triacylglycerols, or cytoplasmic lipid droplets. We show that CzHXK1 is critical for the regulation of genes related to photosynthesis, ketocarotenoid synthesis and fatty acid biosynthesis. Sugars play fundamental regulatory roles in gene expression, physiology, metabolism, and growth in plants and animals, and we introduce a relatively simple, emerging model system to investigate conserved eukaryotic sugar sensing and signaling at the base of the green lineage. In plants, exogenous glucose represses photosynthesis but this phenomenon has been little studied in green algae. Roth et. al. discover through a forward genetics screen in C. zofingiensis that hexokinase 1 is needed to turn off photosynthesis in the presence of glucose and for glucose-mediated upregulation of lipid metabolism. [ABSTRACT FROM AUTHOR]