66 research outputs found
Zelda Binding in the Early Drosophila melanogaster Embryo Marks Regions Subsequently Activated at the Maternal-to-Zygotic Transition
The earliest stages of development in most metazoans are driven by maternally deposited proteins and mRNAs, with widespread transcriptional activation of the zygotic genome occurring hours after fertilization, at a period known as the maternal-to-zygotic transition (MZT). In Drosophila, the MZT is preceded by the transcription of a small number of genes that initiate sex determination, patterning, and other early developmental processes; and the zinc-finger protein Zelda (ZLD) plays a key role in their transcriptional activation. To better understand the mechanisms of ZLD activation and the range of its targets, we used chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-Seq) to map regions bound by ZLD before (mitotic cycle 8), during (mitotic cycle 13), and after (late mitotic cycle 14) the MZT. Although only a handful of genes are transcribed prior to mitotic cycle 10, we identified thousands of regions bound by ZLD in cycle 8 embryos, most of which remain bound through mitotic cycle 14. As expected, early ZLD-bound regions include the promoters and enhancers of genes transcribed at this early stage. However, we also observed ZLD bound at cycle 8 to the promoters of roughly a thousand genes whose first transcription does not occur until the MZT and to virtually all of the thousands of known and presumed enhancers bound at cycle 14 by transcription factors that regulate patterned gene activation during the MZT. The association between early ZLD binding and MZT activity is so strong that ZLD binding alone can be used to identify active promoters and regulatory sequences with high specificity and selectivity. This strong early association of ZLD with regions not active until the MZT suggests that ZLD is not only required for the earliest wave of transcription but also plays a major role in activating the genome at the MZT
Seasonal variation of water uptake of a Quercus suber tree in Central Portugal
Hydraulic redistribution (HR) is the phenomenon
where plant roots transfer water between
soil horizons of different water potential. When dry
soil is a stronger sink for water loss from the plant
than transpiration, water absorbed by roots in wetter
soil horizons is transferred toward, and exuded into
dry soil via flow reversals through the roots. Reverse
flow is a good marker of HR and can serve as a useful
tool to study it over the long-term. Seasonal variation
of water uptake of a Quercus suber tree was studied
from late winter through autumn 2003 at Rio Frio
near Lisbon, Portugal. Sap flow was measured in five
small shallow roots (diameter of 3–4 cm), 1 to 2 m
from the tree trunk and in four azimuths and at
different xylem depths at the trunk base, using the
heat field deformation method (HFD). The pattern of
sap flow differed among lateral roots as soil dried with constant positive flow in three roots and reverse
flow in two other roots during the night when
transpiration ceased. Rain modified the pattern of
flow in these two roots by eliminating reverse flow
and substantially increasing water uptake for transpiration
during the day. The increase in water uptake in
three other roots following rain was not so substantial.
In addition, the flux in individual roots was correlated
to different degrees with the flux at different radial
depths and azimuthal directions in trunk xylem. The
flow in outer trunk xylem seemed to be mostly
consistent with water movement from surface soil
horizons, whereas deep roots seemed to supply water
to the whole cross-section of sapwood. When water
flow substantially decreased in shallow lateral roots
and the outer stem xylem during drought, water flow
in the inner sapwood was maintained, presumably due
to its direct connection to deep roots. Results also
suggest the importance of the sap flow sensor
placement, in relation to sinker roots, as to whether
lateral roots might be found to exhibit reverse flow
during drought. This study is consistent with the
dimorphic rooting habit of Quercus suber trees in
which deep roots access groundwater to supply
superficial roots and the whole tree, when shallow
soil layers were dry
A cross-sectional investigation of regional patterns of diet and cardio-metabolic risk in India
<p>Abstract</p> <p>Background</p> <p>The role of diet in India's rapidly progressing chronic disease epidemic is unclear; moreover, diet may vary considerably across North-South regions.</p> <p>Methods</p> <p>The India Health Study was a multicenter study of men and women aged 35-69, who provided diet, lifestyle, and medical histories, as well as blood pressure, fasting blood, urine, and anthropometric measurements. In each region (Delhi, n = 824; Mumbai, n = 743; Trivandrum, n = 2,247), we identified two dietary patterns with factor analysis. In multiple logistic regression models adjusted for age, gender, education, income, marital status, religion, physical activity, tobacco, alcohol, and total energy intake, we investigated associations between regional dietary patterns and abdominal adiposity, hypertension, diabetes, and dyslipidemia.</p> <p>Results</p> <p>Across the regions, more than 80% of the participants met the criteria for abdominal adiposity and 10 to 28% of participants were considered diabetic. In Delhi, the "fruit and dairy" dietary pattern was positively associated with abdominal adiposity [highest versus lowest tertile, multivariate-adjusted OR and 95% CI: 2.32 (1.03-5.23); P<sub>trend </sub>= 0.008] and hypertension [2.20 (1.47-3.31); P<sub>trend </sub>< 0.0001]. In Trivandrum, the "pulses and rice" pattern was inversely related to diabetes [0.70 (0.51-0.95); P<sub>trend </sub>= 0.03] and the "snacks and sweets" pattern was positively associated with abdominal adiposity [2.05 (1.34-3.14); P<sub>trend </sub>= 0.03]. In Mumbai, the "fruit and vegetable" pattern was inversely associated with hypertension [0.63 (0.40-0.99); P<sub>trend </sub>= 0.05] and the "snack and meat" pattern appeared to be positively associated with abdominal adiposity.</p> <p>Conclusions</p> <p>Cardio-metabolic risk factors were highly prevalent in this population. Across all regions, we found little evidence of a Westernized diet; however, dietary patterns characterized by animal products, fried snacks, or sweets appeared to be positively associated with abdominal adiposity. Conversely, more traditional diets in the Southern regions were inversely related to diabetes and hypertension. Continued investigation of diet, as well as other environmental and biological factors, will be needed to better understand the risk profile in this population and potential means of prevention.</p
Search for gravitational waves associated with gamma-ray bursts detected by Fermi and Swift during the LIGO–Virgo run O3b
We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC–2020 March 27 17:00 UTC). We conduct two independent searches: a generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds no evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate
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