Nitrogen enrichment alters mycorrhizal allocation at five mesic to semiarid grasslands.

Abstract. Arbuscular mycorrhizal (AM) fungi are integral components of grasslands because most plants are associated with interconnected networks of AM hyphae. Mycorrhizae generally facilitate plant uptake of nutrients from the soil. However, mycorrhizal associations are known to vary in their mutualistic function, and there is currently no metric that links AM functioning with fungal colonization of roots. Mycorrhizal structures differ in their physiological and ecological functioning, so changes in AM allocation to intraradical (inside roots) and extraradical (in soil) structures may signal shifts in mycorrhizal function. We hypothesize that the functional equilibrium model applies to AM fungi and that fertilization should reduce allocation to arbuscules, coils, and extraradical hyphae, the fungal structures that are directly involved in nutrient acquisition and transfer to plants. This study compared AM responses to experimental N enrichment at five grasslands distributed across North America. Samples were collected from replicated N-enriched (and some P-enriched) and control plots throughout the growing season for three years. Intraradical AM structures were measured in over 1400 root samples, extraradical hyphal density was measured in over 590 soil samples, and spore biovolume was analyzed in over 400 soil samples. There were significant site ϫ N interactions for spore biovolume, extraradical hyphae, intraradical hyphae, and vesicles. Nitrogen enrichment strongly decreased AM structures at Cedar Creek, the site with the lowest soil N:P, and it increased AM structures at Konza Prairie, the site with the highest soil N:P. As predicted by the functional equilibrium model, in soils with sufficient P, relative allocation to arbuscules, coils, and extraradical hyphae was generally reduced by N enrichment. Allocation to spores and hyphae was most sensitive to fertilization. At the mesic sites, this response was associated with a shift in the relative abundance of Gigasporaceae within AM fungal communities. This study demonstrates that N enrichment impacts mycorrhizal allocation across a wide range of grassland ecosystems. Such changes are important because they suggest an alteration in mycorrhizal functioning that, in turn, may impact plant community composition and ecosystem function

The genomic landscape of balanced cytogenetic abnormalities associated with human congenital anomalies

Despite the clinical significance of balanced chromosomal abnormalities (BCAs), their characterization has largely been restricted to cytogenetic resolution. We explored the landscape of BCAs at nucleotide resolution in 273 subjects with a spectrum of congenital anomalies. Whole-genome sequencing revised 93% of karyotypes and demonstrated complexity that was cryptic to karyotyping in 21% of BCAs, highlighting the limitations of conventional cytogenetic approaches. At least 33.9% of BCAs resulted in gene disruption that likely contributed to the developmental phenotype, 5.2% were associated with pathogenic genomic imbalances, and 7.3% disrupted topologically associated domains (TADs) encompassing known syndromic loci. Remarkably, BCA breakpoints in eight subjects altered a single TAD encompassing MEF2C, a known driver of 5q14.3 microdeletion syndrome, resulting in decreased MEF2C expression. We propose that sequence-level resolution dramatically improves prediction of clinical outcomes for balanced rearrangements and provides insight into new pathogenic mechanisms, such as altered regulation due to changes in chromosome topology

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Measurement of the inclusive isolated-photon cross section in pp collisions at √s = 13 TeV using 36 fb−1 of ATLAS data

The differential cross section for isolated-photon production in pp collisions is measured at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC using an integrated luminosity of 36.1 fb. The differential cross section is presented as a function of the photon transverse energy in different regions of photon pseudorapidity. The differential cross section as a function of the absolute value of the photon pseudorapidity is also presented in different regions of photon transverse energy. Next-to-leading-order QCD calculations from Jetphox and Sherpa as well as next-to-next-to-leading-order QCD calculations from Nnlojet are compared with the measurement, using several parameterisations of the proton parton distribution functions. The predictions provide a good description of the data within the experimental and theoretical uncertainties. [Figure not available: see fulltext.