440 research outputs found
A First Look at Spatially Resolved Balmer Decrements at from JWST NIRISS Slitless Spectroscopy
We present the first results on the spatial distribution of dust attenuation
at traced by the Balmer Decrement, H/H, in
emission-line galaxies using deep JWST NIRISS slitless spectroscopy from the
CAnadian NIRISS Unbiased Cluster Survey (CANUCS). H and H
emission line maps of emission-line galaxies are extracted and stacked in bins
of stellar mass for two grism redshift bins, and
. Surface brightness profiles for the Balmer Decrement are
measured and radial profiles of the dust attenuation towards H,
, are derived. In both redshift bins, the integrated
Balmer Decrement increases with stellar mass. Lower mass
(Log(/M)) galaxies have centrally
concentrated, negative dust attenuation profiles whereas higher mass galaxies
(Log(/M)) have flat dust attenuation
profiles. The total dust obscuration is mild, with on average and
mag in the low and high redshift bins respectively. We model the
typical light profiles of star-forming galaxies at these redshifts and stellar
masses with GALFIT and apply both uniform and radially varying dust attenuation
corrections based on our integrated Balmer Decrements and radial dust
attenuation profiles. If these galaxies were observed with typical JWST NIRSpec
slit spectroscopy ( shutters), on average,
H star formation rates (SFRs) measured after slit-loss corrections
assuming uniform dust attenuation will overestimate the total SFR by and at and
respectively.Comment: 7 pages, 5 figures, submitted to ApJ
GeneCATânovel webtools that combine BLAST and co-expression analyses
The gene co-expression analysis toolbox (GeneCAT) introduces several novel microarray data analyzing tools. First, the multigene co-expression analysis, combined with co-expressed gene networks, provides a more powerful data mining technique than standard, single-gene co-expression analysis. Second, the high-throughput Map-O-Matic tool matches co-expression pattern of multiple query genes to genes present in user-defined subdatabases, and can therefore be used for gene mapping in forward genetic screens. Third, Rosetta combines co-expression analysis with BLAST and can be used to find âtrueâ gene orthologs in the plant model organisms Arabidopsis thaliana and Hordeum vulgare (Barley). GeneCAT is equipped with expression data for the model plant A. thaliana, and first to introduce co-expression mining tools for the monocot Barley. GeneCAT is available at http://genecat.mpg.d
CDM not dead yet: massive high-z Balmer break galaxies are less common than previously reported
Early JWST observations that targeted so-called double-break sources
(attributed to Lyman and Balmer breaks at ), reported a previously unknown
population of very massive, evolved high-redshift galaxies. This surprising
discovery led to a flurry of attempts to explain these objects' unexpected
existence including invoking alternatives to the standard CDM
cosmological paradigm. To test these early results, we adopted the same
double-break candidate galaxy selection criteria to search for such objects in
the JWST images of the CAnadian NIRISS Unbiased Cluster Survey (CANUCS), and
found a sample of 19 sources over five independent CANUCS fields that cover a
total effective area of arcmin at . However, (1) our SED
fits do not yield exceptionally high stellar masses for our candidates, while
(2) spectroscopy of five of the candidates shows that while all five are at
high redshifts, their red colours are due to high-EW emission lines in
star-forming galaxies rather than Balmer breaks in massive, evolved systems.
Additionally, (3) field-to-field variance leads to differences of
dex in the maximum stellar masses measured in the different fields, suggesting
that the early single-field JWST observations may have suffered from cosmic
variance and/or sample bias. Finally, (4) we show that the presence of even a
single massive outlier can dominate conclusions from small samples such as
those in early JWST observations. In conclusion, we find that the double-break
sources in CANUCS are not sufficiently massive or numerous to warrant
questioning the standard CDM paradigm.Comment: V2: correction of display problem of Fig.1 in Chrome browser.
Submitted to MNRAS, 10 pages (+4 in Appendix), 5 figures (+4), 1 table (+1
Laminin and biomimetic extracellular elasticity enhance functional differentiation in mammary epithelia
In the mammary gland, epithelial cells are embedded in a âsoft' environment and become functionally differentiated in culture when exposed to a laminin-rich extracellular matrix gel. Here, we define the processes by which mammary epithelial cells integrate biochemical and mechanical extracellular cues to maintain their differentiated phenotype. We used single cells cultured on top of gels in conditions permissive for ÎČ-casein expression using atomic force microscopy to measure the elasticity of the cells and their underlying substrata. We found that maintenance of ÎČ-casein expression required both laminin signalling and a âsoft' extracellular matrix, as is the case in normal tissues in vivo, and biomimetic intracellular elasticity, as is the case in primary mammary epithelial organoids. Conversely, two hallmarks of breast cancer development, stiffening of the extracellular matrix and loss of laminin signalling, led to the loss of ÎČ-casein expression and non-biomimetic intracellular elasticity. Our data indicate that tissue-specific gene expression is controlled by both the tissues' unique biochemical milieu and mechanical properties, processes involved in maintenance of tissue integrity and protection against tumorigenesis
HSC-CLAUDS survey: The star formation rate functions since z ~ 2 and comparison with hydrodynamical simulations
Star formation rate functions (SFRFs) give an instantaneous view of the
distribution of star formation rates (SFRs) in galaxies at different epochs.
They are a complementary and more stringent test for models than the galaxy
stellar mass function, which gives an integrated view of the past star
formation activity. However, the exploration of SFRFs has been limited thus far
due to difficulties in assessing the SFR from observed quantities and probing
the SFRF over a wide range of SFRs. We overcome these limitations thanks to an
original method that predicts the infrared luminosity from the rest-frame
UV/optical color of a galaxy and then its SFR over a wide range of stellar
masses and redshifts. We applied this technique to the deep imaging survey
HSC-CLAUDS combined with near-infrared and UV photometry. We provide the first
SFR functions with reliable measurements in the high- and low-SFR regimes up to
and compare our results with previous observations and four
state-of-the-art hydrodynamical simulations.Comment: 29 pages, 19 figure
Regulation of mammary gland branching morphogenesis by the extracellular matrix and its remodeling enzymes.
A considerable body of research indicates that mammary gland branching morphogenesis is dependent, in part, on the extracellular matrix (ECM), ECM-receptors, such as integrins and other ECM receptors, and ECM-degrading enzymes, including matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs). There is some evidence that these ECM cues affect one or more of the following processes: cell survival, polarity, proliferation, differentiation, adhesion, and migration. Both three-dimensional culture models and genetic manipulations of the mouse mammary gland have been used to study the signaling pathways that affect these processes. However, the precise mechanisms of ECM-directed mammary morphogenesis are not well understood. Mammary morphogenesis involves epithelial 'invasion' of adipose tissue, a process akin to invasion by breast cancer cells, although the former is a highly regulated developmental process. How these morphogenic pathways are integrated in the normal gland and how they become dysregulated and subverted in the progression of breast cancer also remain largely unanswered questions
The Sparkler: Evolved High-Redshift Globular Clusters Captured by JWST
Using data from JWST, we analyze the compact sources ("sparkles") located
around a remarkable galaxy (the "Sparkler") that is
strongly gravitationally lensed by the galaxy cluster SMACS
J0723.3-7327. Several of these compact sources can be cross-identified in
multiple images, making it clear that they are associated with the host galaxy.
Combining data from JWST's {\em Near-Infrared Camera} (NIRCam) with archival
data from the {\em Hubble Space Telescope} (HST), we perform 0.4-4.4m
photometry on these objects, finding several of them to be very red and
consistent with the colors of quenched, old stellar systems. Morphological fits
confirm that these red sources are spatially unresolved even in strongly
magnified JWST/NIRCam images, while JWST/NIRISS spectra show [OIII]5007
emission in the body of the Sparkler but no indication of star formation in the
red compact sparkles. The most natural interpretation of these compact red
companions to the Sparkler is that they are evolved globular clusters seen at
. Applying \textsc{Dense Basis} SED-fitting to the sample, we infer
formation redshifts of for these globular cluster
candidates, corresponding to ages of Gyr at the epoch of
observation and a formation time just 0.5~Gyr after the Big Bang. If
confirmed with additional spectroscopy, these red, compact "sparkles" represent
the first evolved globular clusters found at high redshift, could be amongst
the earliest observed objects to have quenched their star formation in the
Universe, and may open a new window into understanding globular cluster
formation. Data and code to reproduce our results will be made available at
\faGithub\href{https://niriss.github.io/sparkler.html}{http://canucs-jwst.com/sparkler.html}.Comment: Submitted to ApJL. Comments are welcome. Data and code to reproduce
our results will be made available at niriss.github.io/sparkler.htm
Impacts of climate change on plant diseases â opinions and trends
There has been a remarkable scientific output on the topic of how climate change is likely to affect plant diseases in the coming decades. This review addresses the need for review of this burgeoning literature by summarizing opinions of previous reviews and trends in recent studies on the impacts of climate change on plant health. Sudden Oak Death is used as an introductory case study: Californian forests could become even more susceptible to this emerging plant disease, if spring precipitations will be accompanied by warmer temperatures, although climate shifts may also affect the current synchronicity between host cambium activity and pathogen colonization rate. A summary of observed and predicted climate changes, as well as of direct effects of climate change on pathosystems, is provided. Prediction and management of climate change effects on plant health are complicated by indirect effects and the interactions with global change drivers. Uncertainty in models of plant disease development under climate change calls for a diversity of management strategies, from more participatory approaches to interdisciplinary science. Involvement of stakeholders and scientists from outside plant pathology shows the importance of trade-offs, for example in the land-sharing vs. sparing debate. Further research is needed on climate change and plant health in mountain, boreal, Mediterranean and tropical regions, with multiple climate change factors and scenarios (including our responses to it, e.g. the assisted migration of plants), in relation to endophytes, viruses and mycorrhiza, using long-term and large-scale datasets and considering various plant disease control methods
KORRIGAN1 Interacts Specifically with Integral Components of the Cellulose Synthase Machinery
Cellulose is synthesized by the so called rosette protein complex and the catalytic subunits of this complex are the cellulose synthases (CESAs). It is thought that the rosette complexes in the primary and secondary cell walls each contains at least three different non-redundant cellulose synthases. In addition to the CESA proteins, cellulose biosynthesis almost certainly requires the action of other proteins, although few have been identified and little is known about the biochemical role of those that have been identified. One of these proteins is KORRIGAN (KOR1). Mutant analysis of this protein in Arabidopsis thaliana showed altered cellulose content in both the primary and secondary cell wall. KOR1 is thought to be required for cellulose synthesis acting as a cellulase at the plasma membraneâcell wall interface. KOR1 has recently been shown to interact with the primary cellulose synthase rosette complex however direct interaction with that of the secondary cell wall has never been demonstrated. Using various methods, both in vitro and in planta, it was shown that KOR1 interacts specifically with only two of the secondary CESA proteins. The KOR1 protein domain(s) involved in the interaction with the CESA proteins were also identified by analyzing the interaction of truncated forms of KOR1 with CESA proteins. The KOR1 transmembrane domain has shown to be required for the interaction between KOR1 and the different CESAs, as well as for higher oligomer formation of KOR1
A fluorescent hormone biosensor reveals the dynamics of jasmonate signalling in plants
Activated forms of jasmonic acid (JA) are central signals coordinating plant responses to stresses, yet tools to analyse their spatial and temporal distribution are lacking. Here we describe a JA perception biosensor termed Jas9-VENUS that allows the quantification of dynamic changes in JA distribution in response to stress with high spatiotemporal sensitivity. We show that Jas9-VENUS abundance is dependent on bioactive JA isoforms, the COI1 co-receptor, a functional Jas motif and proteasome activity. We demonstrate the utility of Jas9-VENUS to analyse responses to JA in planta at a cellular scale, both quantitatively and dynamically. This included using Jas9-VENUS to determine the cotyledon-to-root JA signal velocities on wounding, revealing two distinct phases of JA activity in the root. Our results demonstrate the value of developing quantitative sensors such as Jas9-VENUS to provide high-resolution spatiotemporal data about hormone distribution in response to plant abiotic and biotic stresses
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