20 research outputs found
"No waving mutant": caratterizzazione fenotipica e molecolare di un mutante "T-DNA tagged" di Arabidopsis thaliana
In uno studio compiuto sul trascrittoma di Arabidopsis thaliana in condizioni anossiche sono stati identificati alcuni geni che mostrano una rapida e significativa induzione in seguito all’abbassamento delle concentrazioni di ossigeno disponibile nell’ambiente. Di questi geni sono disponibili i relativi mutanti inserzionali “T-DNA tagged” e fra questi ne è stato identificato uno che presenta interessanti caratteristiche fenotipiche. Il gene in questione è At3g03270, appartenente alla famiglia delle Universal Stress Protein, le quali sembrano svolgere un ruolo importante nelle vie di signalling generate da stress abiotici e biotici. Questo lavoro sperimentale si è occupato di caratterizzare le linee Salk_042828 e Salk_136373, che costituiscono due diversi mutanti inserzionali per il gene preso in considerazione. Dal punto di vista fenotipico sono stati rilevati una serie di caratteri molto interessanti: la linea Salk_042828, cresciuta in piastre verticali poste ad una inclinazione di 75°, mostra radici più corte con ramificazioni ridotte e l’assenza del fenomeno noto come “root waving” se confrontata con il relativo wild type e la linea Salk_136373. La radice primaria è caratterizzata inoltre da un sovrapproduzione di peli radicali. Le foglie sono accartocciate e più affusolate rispetto al wild type ed hanno un comportamento costitutivamente iponastico, con il picciolo che forma un angolo più ampio con il terreno rispetto al wild type. La linea Salk_042828 mostra inoltre una maggiore sensibilità a trattamenti anossici e di sommersione. Dall’analisi trascrizionale è stato infine individuato un cluster di geni particolarmente indotti coinvolti nella risposta alle “reactive oxygen species” (ROS).
Per comprendere se la mutazione del gene At3g03270 nella linea Salk_042828 è l’unica responsabile del fenotipo osservato sono state adottate diverse strategie di transgenesi: fenocopiare la mutazione nel wild type, overesprimendo la sequenza genica At3g03270 non mutata nella linea wild type, oppure seguire la strategia della complementazione overesprimendo il gene d’interesse nella sua forma wild type all’interno delle linee mutanti. Le linee transgeniche risultanti aiuteranno a capire se la mutazione in questione è di tipo “gain” o “loss of function”
Misexpression of a chloroplast aspartyl protease leads to severe growth defects and alters carbohydrate metabolism in Arabidopsis
The crucial role of carbohydrate in plant growth and morphogenesis is widely recognized. In this study, we describe the characterization of nana, a dwarf Arabidopsis (Arabidopsis thaliana) mutant impaired in carbohydrate metabolism. We show that the nana dwarf phenotype was accompanied by altered leaf morphology and a delayed flowering time. Our genetic and molecular data indicate that the mutation in nana is due to a transfer DNA insertion in the promoter region of a gene encoding a chloroplast-located aspartyl protease that alters its pattern of expression. Overexpression of the gene (oxNANA) phenocopies the mutation. Both nana and oxNANA display alterations in carbohydrate content, and the extent of these changes varies depending on growth light intensity. In particular, in low light, soluble sugar levels are lower and do not show the daily fluctuations observed in wild-type plants. Moreover, nana and oxNANA are defective in the expression of some genes implicated in sugar metabolism and photosynthetic light harvesting. Interestingly, some chloroplast-encoded genes as well as genes whose products seem to be involved in retrograde signaling appear to be down-regulated. These findings suggest that the NANA aspartic protease has an important regulatory function in chloroplasts that not only influences photosynthetic carbon metabolism but also plastid and nuclear gene expression
A fast-rotator post-starburst galaxy quenched by supermassive black-hole feedback at z=3
There is compelling evidence that the most massive galaxies in the Universe
stopped forming stars due to the time-integrated feedback from their central
super-massive black holes (SMBHs). However, the exact quenching mechanism is
not yet understood, because local massive galaxies were quenched billions of
years ago. We present JWST/NIRSpec integral-field spectroscopy observations of
GS-10578, a massive, quiescent galaxy at redshift z=3.064. From the spectrum we
infer that the galaxy has a stellar mass of MSun
and a dynamical mass MSun. Half of its
stellar mass formed at z=3.7-4.6, and the system is now quiescent, with the
current star-formation rate SFR<9 MSun/yr. We detect ionised- and neutral-gas
outflows traced by [OIII] emission and NaI absorption. Outflow velocities reach
1,000 km/s, comparable to the galaxy escape velocity and
too high to be explained by star formation alone. GS-10578 hosts an Active
Galactic Nucleus (AGN), evidence that these outflows are due to SMBH feedback.
The outflow rates are 0.14-2.9 and 30-300 MSun/yr for the ionised and neutral
phases, respectively. The neutral outflow rate is ten times higher than the
SFR, hence this is direct evidence for ejective SMBH feedback, with
mass-loading capable of interrupting star formation by rapidly removing its
fuel. Stellar kinematics show ordered rotation, with spin parameter
, meaning GS-10578 is rotation supported. This study
shows direct evidence for ejective AGN feedback in a massive, recently quenched
galaxy, thus clarifying how SMBHs quench their hosts. Quenching can occur
without destroying the stellar disc.Comment: 40 pages, 9 figures, submitted to Nat. Ast., comments welcome
JADES: Probing interstellar medium conditions at with ultra-deep JWST/NIRSpec spectroscopy
We present emission line ratios from a sample of 26 Lyman break galaxies from
with , measured from ultra-deep
JWST/NIRSpec MSA spectroscopy from JADES. We use 28 hour deep PRISM/CLEAR and 7
hour deep G395M/F290LP observations to measure, or place strong constraints on,
ratios of widely studied rest-frame optical emission lines including H,
H, [OII] 3726,3729, [NeIII] 3869, [OIII]
4959, [OIII] 5007, [OI] 6300, [NII] 6583,
and [SII] 6716,6731 in individual spectra. We find that
the emission line ratios exhibited by these galaxies occupy
clearly distinct regions of line-ratio space compared to typical z~0-3
galaxies, instead being more consistent with extreme populations of
lower-redshift galaxies. This is best illustrated by the [OIII]/[OII] ratio,
tracing interstellar medium (ISM) ionisation, in which we observe more than
half of our sample to have [OIII]/[OII]>10. Our high signal-to-noise spectra
reveal more than an order of magnitude of scatter in line ratios such as
[OII]/H and [OIII]/[OII], indicating significant diversity in the ISM
conditions within the sample. We find no convincing detections of [NII] in our
sample, either in individual galaxies, or a stack of all G395M/F290LP spectra.
The emission line ratios observed in our sample are generally consistent with
galaxies with extremely high ionisation parameters (log ), and a
range of metallicities spanning from to higher than
, suggesting we are probing low-metallicity systems
undergoing periods of rapid star-formation, driving strong radiation fields.
These results highlight the value of deep observations in constraining the
properties of individual galaxies, and hence probing diversity within galaxy
population.Comment: 20 pages, 9 figures, submitted to Astronomy & Astrophysics, updated
values in table
The JADES Origins Field: A New JWST Deep Field in the JADES Second NIRCam Data Release
We summarize the properties and initial data release of the JADES Origins
Field (JOF), which will soon be the deepest imaging field yet observed with the
James Webb Space Telescope (JWST). This field falls within the GOODS-S region
about 8' south-west of the Hubble Ultra Deep Field (HUDF), where it was formed
initially in Cycle 1 as a parallel field of HUDF spectroscopic observations
within the JWST Advanced Deep Extragalactic Survey (JADES). This imaging will
be greatly extended in Cycle 2 program 3215, which will observe the JOF for 5
days in six medium-band filters, seeking robust candidates for z>15 galaxies.
This program will also include ultra-deep parallel NIRSpec spectroscopy (up to
104 hours on-source, summing over the dispersion modes) on the HUDF. Cycle 3
observations from program 4540 will add 20 hours of NIRCam slitless
spectroscopy to the JOF. With these three campaigns, the JOF will be observed
for 380 open-shutter hours with NIRCam using 15 imaging filters and 2 grism
bandpasses. Further, parts of the JOF have deep 43 hr MIRI observations in
F770W. Taken together, the JOF will soon be one of the most compelling deep
fields available with JWST and a powerful window into the early Universe. This
paper presents the second data release from JADES, featuring the imaging and
catalogs from the year 1 JOF observations.Comment: Submitted to ApJ Supplement. Images and catalogs are available at
https://archive.stsci.edu/hlsp/jades . A FITSmap portal to view the images is
at https://jades.idies.jhu.ed
JADES NIRSpec Spectroscopy of GN-z11: Lyman- emission and possible enhanced nitrogen abundance in a luminous galaxy
We present JADES JWST/NIRSpec spectroscopy of GN-z11, the most luminous
candidate Lyman break galaxy in the GOODS-North field with
. We derive a redshift of (lower than previous
determinations) based on multiple emission lines in our low and medium
resolution spectra over m. We significantly detect the continuum
and measure a blue rest-UV spectral slope of . Remarkably, we see
spatially-extended Lyman- in emission (despite the highly-neutral IGM
expected at this early epoch), offset 555 km/s redward of the systemic
redshift. From our measurements of collisionally-excited lines of both low- and
high-ionization (including [O II] , [Ne III] and C
III] ) we infer a high ionization parameter (). We
detect the rarely-seen N IV] and N III] lines in
both our low and medium resolution spectra, with other high ionization lines
seen in low resolution spectrum such as He II (blended with O III]) and C IV
(with a possible P-Cygni profile). Based on the observed rest-UV line ratios,
we cannot conclusively rule out photoionization from AGN. The high C III]/He II
ratios, however, suggest a likely star-formation explanation. If the observed
emission lines are powered by star formation, then the strong N III]
observed may imply an unusually high abundance. Balmer
emission lines (H, H) are also detected, and if powered by star
formation rather than an AGN we infer a star formation rate of (depending on the IMF) and low dust attenuation. Our
NIRSpec spectroscopy confirms that GN-z11 is a remarkable galaxy with extreme
properties seen 430 Myr after the Big Bang.Comment: Submitted to Astronomy & Astrophysics, 14 pages, 9 figure
Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study
Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research