MtNramp1 mediates iron import in rhizobia-infected Medicago truncatula cells.

Symbiotic nitrogen fixation is a process that requires relatively high quantities of iron provided by the host legume. Using synchrotron-based X-ray fluorescence, we have determined that this iron is released from the vasculature into the apoplast of zone II of M. truncatula nodules. This overlaps with the distribution of MtNramp1, a plasma membrane iron importer. The importance of MtNramp1 in iron transport for nitrogen fixation is indicated by the 60% reduction of nitrogenase activity observed in knock-down lines, most likely due to deficient incorporation of this essential metal cofactor at the necessary levels

The global abundance of tree palms

Aim: Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location: Tropical and subtropical moist forests. Time period: Current. Major taxa studied: Palms (Arecaceae). Methods: We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results: On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long‐term climate stability. Life‐form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non‐tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above‐ground biomass, but the magnitude and direction of the effect require additional work. Conclusions: Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests

Tree diversity and above-ground biomass in the South America Cerrado biome and their conservation implications

Less than half of the original two million square kilometers of the Cerrado vegetation remains standing, and there are still many uncertainties as to how to conserve and prioritize remaining areas effectively. A key limitation is the continuing lack of geographically-extensive evaluation of ecosystem-level properties across the biome. Here we sought to address this gap by comparing the woody vegetation of the typical cerrado of the Cerrado–Amazonia Transition with that of the core area of the Cerrado in terms of both tree diversity and vegetation biomass. We used 21 one-hectare plots in the transition and 18 in the core to compare key structural parameters (tree height, basal area, and above-ground biomass), and diversity metrics between the regions. We also evaluated the effects of temperature and precipitation on biomass, as well as explored the species diversity versus biomass relationship. We found, for the first time, both that the typical cerrado at the transition holds substantially more biomass than at the core, and that higher temperature and greater precipitation can explain this difference. By contrast, plot-level alpha diversity was almost identical in the two regions. Finally, contrary to some theoretical expectations, we found no positive relationship between species diversity and biomass for the Cerrado woody vegetation. This has implications for the development of effective conservation measures, given that areas with high biomass and importance for the compensation of greenhouse gas emissions are often not those with the greatest diversity

Elevated fractional exhaled nitric oxide and blood eosinophil counts are associated with a 17q21 asthma risk allele in adult subjects

Elizabeth A Schwantes,1 Michael D Evans,2 Alex Cuskey,1 Alex Burford,1 Judith A Smith,3 Robert F Lemanske Jr,3 Nizar N Jarjour,1 Sameer K Mathur1 1Division of Allergy, Pulmonary and Critical Care, Department of Medicine, 2Department of Biostatistics and Medical Informatics, 3Division of Allergy, Immunology and Rheumatology, Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA Background and objectives: Genome-wide association studies identified single-nucleotide polymorphisms (SNPs) at the 17q21 locus conferring increased risk for childhood-onset asthma. Little is known about how these SNPs impact adult asthma patients. We sought to examine an adult population for associations between rs7216389 (17q21-associated SNP) and features of asthma including fractional exhaled nitric oxide (FeNO), eosinophil counts, and age of asthma onset. Methods: Subjects were genotyped at SNP rs7216389. The geometric mean of FeNO measurements and peripheral blood eosinophil counts from 2008 to 2015 were collected. Demographics and medical history were collected including self-reported allergy diagnoses and age of asthma onset. Eosinophils, monocytes, and peripheral blood mononuclear cells (PBMCs) were isolated for the examination of ORMDL3 expression. Results: FeNO levels from 157 genotyped subjects (31CC, 72CT, and 54TT) and peripheral eosinophil counts from 252 genotyped subjects (46CC, 122CT, and 84TT) were analyzed. In a sub-group analysis of asthma subjects, the number of attributable T alleles was associated with significantly lower age of asthma onset (P=0.03) and greater FeNO levels (geometric mean 30.0 ppb TT, 20.0 ppb CT, 20.0 ppb CC, P=0.02). In the total cohort of subjects, the T allele was associated with a higher percentage of individual eosinophil counts >200/mm3 (45% TT, 26% CT, 24% CC, P=0.005). Eosinophils expressed ORMDL3 mRNA and protein. Conclusion: In adult subjects, the number of T alleles at SNP rs7216389 corresponds to significantly greater FeNO levels and peripheral eosinophil counts. The expression of ORMDL3 in eosinophils suggests that they may participate in mediating the asthma risk associated with the 17q21 locus. Keywords: asthma, eosinophils, fractional exhaled nitric oxide, 17q2

Annual variation in soil respiration and its component parts in two structurally contrasting woody savannas in Central Brazil

Background and aims: Due to the high spatial and temporal variation in soil CO₂ efflux, terrestrial carbon budgets rely on a detailed understanding of the drivers of soil respiration from a diverse range of ecosystems and climate zones. In this study we aim to evaluate the independent influence of vegetation structure and climate on soil CO₂ efflux within cerrado ecosystems. \ud \ud Methods: We examine the seasonal and diel variation of soil CO₂ efflux, including its autotrophic and heterotrophic components, within two adjacent and structurally contrasting woody savannas in central Brazil. \ud \ud Principle results: We found no significant difference in the annual soil CO₂ efflux between the two stands (p=0.53) despite a clear disparity in both LAI (p<0.01) and leaf litterfall (p<0.01). The mean annual loss of carbon from the soil was 17.32(± 1.48) Mg Cha⁻¹ of which approximately 63% was accounted for by autotrophic respiration. The relative contribution of autotrophic respiration varied seasonally between 55% in the wet season to 79% of the total soil CO₂ efflux in the dry season. Furthermore, seasonal fluctuations of all the soil respiration components were strongly correlated with soil moisture (R²=0.79-0.90, p<0.01). \ud \ud Conclusions: Across these two structurally distinct cerrado stands, seasonal variations in rainfall, was the main driver of soil CO₂ efflux and its components. Consequently, soil respiration within these ecosystems is likely to be highly sensitive to any changes in seasonal precipitation patterns