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The archaeological record shows that large pre-Inca agricultural systems supported settlements for centuries around the ravines and oases of northern Chile’s hyperarid Atacama Desert. This raises questions about how such productivity was achieved and sustained, and its social implications. Using isotopic data of well-preserved ancient plant remains from Atacama sites, we show a dramatic increase in crop nitrogen isotope values (δ15N) from around ad 1000. Maize was most affected, with δ15N values as high as +30‰, and human bone collagen following a similar trend; moreover, their carbon isotope values (δ13C) indicate a considerable increase in the consumption of maize at the same time. We attribute the shift to extremely high δ15N values—the highest in the world for archaeological plants—to the use of seabird guano to fertilize crops. Guano—‘white gold’ as it came to be called—thus sustained agricultural intensification, supporting a substantial population in an otherwise extreme environment. The source of pre-Inca agriculture in the Atacama Desert of Chile has been the subject of multiple theories, but this Article uses preserved maize remains to deduce that coastal guano deposits were utilized in an impressive display of social and ecological sophistication.

Coordination between plant development and nutrient availability ensures a suitable supply of macromolecules for growth and developmental programs. Nitrate is an important source of nitrogen (N) that acts as a signal molecule to modulate gene expression, physiological, growth and developmental responses throughout the life of the plant. New key players in the nitrate signaling pathway have been described and knowledge of the molecular mechanics of how it impacts growth and developmental processes is increasing fast. Importantly, mechanisms for nitrate-control of growth and developmental processes have been proposed for both local as well as systemic responses. This article provides a synthesis of recent insights into molecular mechanisms by which nitrate impacts growth and development over Arabidopsis life-cycle.

International audience; The environmental fluctuations of a constantly evolving world can mould a changing context, often unfavourable to sessile organisms that must adjust their resource allocation between both resistance or tolerance mechanisms and growth. Plants bear the fascinating ability to survive and thrive under extreme conditions, a capacity that has always attracted the curiosity of humans, who have discovered and improved species capable of meeting our physiological needs. In this context, plant research has produced a great wealth of knowledge on the responses of plants to a range of abiotic stresses, mostly considering model species and/or controlled conditions. However, there is still minimal comprehension of plant adaptations and acclimations to extreme environments, which cries out for future investigations. In this article, we examined the main advances in understanding the adapted traits fixed through evolution that allowed for plant resistance against abiotic stress in extreme natural ecosystems. Spatio-temporal adaptations from extremophile plant species are described from morpho-anatomical features to physiological function and metabolic pathways adjustments. Considering that metabolism is at the heart of plant adaptations, a focus is given to the study of primary and secondary metabolic adjustments as well as redox metabolism under extreme conditions. This article further casts a critical glance at the main successes in studying extreme environments and examines some of the challenges and opportunities this research offers, especially considering the possible interaction with ecology and metaphenomics.

Complex I (also known as NADH-ubiquinone oxidoreductase) deficiency is the most frequent mitochondrial disorder present in childhood. NADH-ubiquinone oxidoreductase iron-sulfur protein 3 (NDUFS3) is a catalytic subunit of the mitochondrial complex I; NDUFS3 is conserved from bacteria and essential for complex I function. Mutations affecting complex I, including in the Ndufs3 gene, cause fatal neurodegenerative diseases, such as Leigh syndrome. No treatment is available for these conditions. We developed and performed a detailed molecular characterization of a neuron-specific Ndufs3 conditional KO mouse model. We showed that deletion of Ndufs3 in forebrain neurons reduced complex I activity, altered brain energy metabolism, and increased locomotor activity with impaired motor coordination, balance, and stereotyped behavior. Metabolomics analyses showed an increase of glycolysis intermediates, suggesting an adaptive response to the complex I defect. Administration of metformin to these mice delayed the onset of the neurological symptoms but not of neuronal loss. This improvement was likely related to enhancement of glucose uptake and utilization, which are known effects of metformin in the brain. Despite reports that metformin inhibits complex I activity, our findings did not show worsening a complex I defect nor increases in lactic acid, suggesting that metformin should be further evaluated for use in patients with mitochondrial encephalopathies., Metformin delays onset of mitochondrial encephalopathy in a CNS model of mitochondrial oxidative phosphorylation defect.

Future climate change has the potential to alter the distribution and prevalence of plant pathogens, which may have significant implications for both agricultural crops and natural plant communities. However, there are few long-term datasets against which modelled predictions of pathogen responses to climate change can be tested. Here, we use 18S metabarcoding of 28 rodent middens (solidified deposits of rodent coprolites and nesting material) from the Central Atacama, spanning the last ca. 49 ka, to provide the first long-term late Quaternary record of change in plant pathogen communities in response to changing climate. Plant pathogen richness was significantly greater in middens deposited during the Central Andean Pluvial Event (CAPE); a period of increased precipitation between 17.5–8.5 ka. Moreover, the occurrence frequency of Pucciniaceae (rust fungi) was significantly greater during the CAPE, and the highest relative abundances for five additional potentially pathogenic taxa also occurred during this period. The results demonstrate the promising potential for ancient DNA analysis of late Quaternary samples to reveal insights into how plant pathogens responded to past climatic and environmental change, which could help predict how pathogens may responded to future change.

Understanding the factors that modulate bacterial community assembly in natural soils is a longstanding challenge in microbial community ecology. In this work, we compared two microbial co-occurrence networks representing bacterial soil communities from two different sections of a pH, temperature and humidity gradient occurring along a western slope of the Andes in the Atacama Desert. In doing so, a topological graph alignment of co-occurrence networks was used to determine the impact of a shift in environmental variables on OTUs taxonomic composition and their relationships. We observed that a fraction of association patterns identified in the co-occurrence networks are persistent despite large environmental variation. This apparent resilience seems to be due to: (1) a proportion of OTUs that persist across the gradient and maintain similar association patterns within the community and (2) bacterial community ecological rearrangements, where an important fraction of the OTUs come to fill the ecological roles of other OTUs in the other network. Actually, potential functional features suggest a fundamental role of persistent OTUs along the soil gradient involving nitrogen fixation. Our results allow identifying factors that induce changes in microbial assemblage configuration, altering specific bacterial soil functions and interactions within the microbial communities in natural environments.

Neuromuscular disorders with defects in the mitochondrial ATP-generating system affect a large number of children and adults worldwide, but remain without treatment. We used a mouse model of mitochondrial myopathy, caused by a cytochrome c oxidase deficiency, to evaluate the effect of induced mitochondrial biogenesis on the course of the disease. Mitochondrial biogenesis was induced either by transgenic expression of peroxisome proliferator-activated receptor gamma (PPARgamma) coactivator alpha (PGC-1alpha) in skeletal muscle or by administration of bezafibrate, a PPAR panagonist. Both strategies successfully stimulated residual respiratory capacity in muscle tissue. Mitochondrial proliferation resulted in an enhanced OXPHOS capacity per muscle mass. As a consequence, ATP levels were conserved resulting in a delayed onset of the myopathy and a markedly prolonged life span. Thus, induction of mitochondrial biogenesis through pharmacological or metabolic modulation of the PPAR/PGC-1alpha pathway promises to be an effective therapeutic approach for mitochondrial disorders.

Acute pharmacological activation of adenosine monophosphate (AMP)-kinase using 5-aminoimidazole-4-carboxamide-1-b-D-ribofuranoside (AICAR) has been shown to improve muscle mitochondrial function by increasing mitochondrial biogenesis. We asked whether prolonged AICAR treatment is beneficial in a mouse model of slowly progressing mitochondrial myopathy (Cox10-Mef2c-Cre), and whether the compensatory mechanism is indeed an increase in mitochondrial biogenesis. We treated the animals for 3 months and found that sustained AMP-dependent kinase activation improved cytochrome c oxidase activity, rescued the motor phenotype and delayed the onset of the myopathy. This improvement was observed whether treatment started before or after the onset of the disease. We found that AICAR increased skeletal muscle regeneration thereby decreasing the levels of deleted Cox10-floxed alleles. We conclude that although increase in mitochondrial biogenesis and other pathways may contribute, the main mechanism by which AICAR improves the myopathy phenotype is by promoting muscle regeneration.