Clathrin-mediated endocytosis depends on polymerization of a branched actin network to provide force for membrane invagination. A key regulator in branched actin network formation is actin capping ...protein (CP), which binds to the barbed end of actin filaments to prevent the addition or loss of actin subunits. CP was thought to stochastically bind actin filaments, but recent evidence shows CP is regulated by a group of proteins containing CP-interacting (CPI) motifs. Importantly, how CPI motif proteins function together to regulate CP is poorly understood. Here, we show Aim21 and Bsp1 work synergistically to recruit CP to the endocytic actin network in budding yeast through their CPI motifs, which also allosterically modulate capping strength. In contrast, twinfilin works downstream of CP recruitment, regulating the turnover of CP through its CPI motif and a non-allosteric mechanism. Collectively, our findings reveal how three CPI motif proteins work together to regulate CP in a stepwise fashion during endocytosis.
DNA end resection plays a critical function in DNA double-strand break repair pathway choice. Resected DNA ends are refractory to end-joining mechanisms and are instead channeled to homology-directed ...repair. Using biochemical, genetic, and imaging methods, we show that phosphorylation of Saccharomyces cerevisiae Sae2 controls its capacity to promote the Mre11-Rad50-Xrs2 (MRX) nuclease to initiate resection of blocked DNA ends by at least two distinct mechanisms. First, DNA damage and cell cycle-dependent phosphorylation leads to Sae2 tetramerization. Second, and independently, phosphorylation of the conserved C-terminal domain of Sae2 is a prerequisite for its physical interaction with Rad50, which is also crucial to promote the MRX endonuclease. The lack of this interaction explains the phenotype of rad50S mutants defective in the processing of Spo11-bound DNA ends during meiotic recombination. Our results define how phosphorylation controls the initiation of DNA end resection and therefore the choice between the key DNA double-strand break repair mechanisms.
We present a new technique for modelling submillimetre galaxies (SMGs): the 'Count Matching' approach. Using light cones drawn from a semi-analytic model of galaxy formation, we choose physical ...galaxy properties given by the model as proxies for their submillimetre luminosities, assuming a monotonic relationship. As recent interferometric observations of the Extended Chandra Deep Field-South show that the brightest sources detected by single-dish telescopes are comprised by emission from multiple fainter sources, we assign the submillimetre fluxes so that the combined Large APEX BOlometer CAmera (LABOCA) plus bright-end Atacama Large Millimeter/submillimeter Array observed number counts for this field are reproduced. After turning the model catalogues given by the proxies into submillimetre maps, we perform a source extraction to include the effects of the observational process on the recovered counts and galaxy properties. We find that for all proxies, there are lines of sight giving counts consistent with those derived from LABOCA observations, even for input sources with randomized positions in the simulated map. Comparing the recovered redshift, stellar mass and host halo mass distributions for model SMGs with observational data, we find that the best among the proposed proxies is that in which the submillimetre luminosity increases monotonically with the product between dust mass and star formation rate (SFR). This proxy naturally reproduces a positive trend between SFR and bolometric IR luminosity. The majority of components of blended sources are spatially unassociated.
ABSTRACT
All estimators of the two-point correlation function are based on a random catalogue, a set of points with no intrinsic clustering following the selection function of a survey. High-accuracy ...estimates require the use of large random catalogues, which imply a high computational cost. We propose to replace the standard random catalogues by glass-like point distributions or glass catalogues whose power spectrum P(k) ∝ k4 exhibits significantly less power on scales larger than the mean interparticle separation than a Poisson distribution with the same number of points. We show that these distributions can be obtained by iteratively applying the technique of Zeldovich reconstruction commonly used in studies of baryon acoustic oscillations (BAO). We provide a modified version of the widely used Landy–Szalay estimator of the correlation function adapted to the use of glass catalogues and compare its performance with the results obtained using random samples. Our results show that glass-like samples do not add any bias with respect to the results obtained using Poisson distributions. On scales larger than the mean interparticle separation of the glass catalogues, the modified estimator leads to a significant reduction of the variance of the Legendre multipoles ξℓ(s) with respect to the standard Landy–Szalay results with the same number of points. The size of the glass catalogue required to achieve a given accuracy in the correlation function is significantly smaller than when using random samples. Their use could help us to drastically reduce the computational cost of configuration-space clustering analysis of future surveys while maintaining high-accuracy requirements.
It is well known that proteins denature under high pressure. The mechanism that underlies such a process is still not clearly understood, however, giving way to controversial interpretations. Using ...molecular dynamics simulation on systems that may be regarded experimentally as limiting examples of the effect of high pressure on globular proteins, such as lysozyme and apomyoglobin, we have effectively reproduced such similarities and differences in behavior as are interpreted from experiment. From the analysis of such data, we explain the experimental evidence at hand through the effect of pressure on the change of water structure, and hence the weakening of the hydrophobic effect that is known to be the main driving force in protein folding.
For social bees, an understudied step in evaluating pesticide risk is how contaminated food entering colonies affects residing offspring development and maturation. For instance, neurotoxic ...insecticide compounds in food could affect central nervous system development predisposing individuals to become poorer task performers later-in-life. Studying bumblebee colonies provisioned with neonicotinoid spiked nectar substitute, we measured brain volume and learning behaviour of 3 or 12-day old adults that had experienced in-hive exposure during brood and/or early-stage adult development. Micro-computed tomography scanning and segmentation of multiple brain neuropils showed exposure during either of the developmental stages caused reduced mushroom body calycal growth relative to unexposed workers. Associated with this was a lower probability of responding to a sucrose reward and lower learning performance in an olfactory conditioning test. While calycal volume of control workers positively correlated with learning score, this relationship was absent for exposed workers indicating neuropil functional impairment. Comparison of 3- and 12-day adults exposed during brood development showed a similar degree of reduced calycal volume and impaired behaviour highlighting lasting and irrecoverable effects from exposure despite no adult exposure. Our findings help explain how the onset of pesticide exposure to whole colonies can lead to lag-effects on growth and resultant dysfunction.
Thermal performance curves have provided a common framework to study the impact of temperature in biological systems. However, few generalities have emerged to date. Here, we combine an experimental ...approach with theoretical analyses to demonstrate that performance curves are expected to vary predictably with the levels of biological organization. We measured rates of enzymatic reactions, organismal performance and population viability in
acclimated to different thermal conditions and show that performance curves become narrower with thermal optima shifting towards lower temperatures at higher levels or organization. We then explain these results on theoretical grounds, showing that this pattern reflects the cumulative impact of asymmetric thermal effects that piles up with complexity. These results and the proposed framework are important to understand how organisms, populations and ecological communities might respond to changing thermal conditions.
Cosmic voids are prominent features of the Universe, encoding relevant information of the growth and evolution of structure through their dynamics. Here, we perform a statistical study of the global ...motion of cosmic voids using both a numerical simulation and observational data. Their relation to large-scale mass flows and the physical effects that drive those motions. We analyse the bulk motions of voids, finding void mean bulk velocities in the range 300–400 km s−1, depending on void size and the large-scale environment. Statistically, small voids move faster, and voids in relatively higher density environments have higher bulk velocities. Also, we find large-scale overdensities (underdensities) along (opposite to) the void motion direction, suggesting that void motions respond to a pull–push mechanism. Our analysis suggests that their relative motions are generated by large-scale density fluctuations. In agreement with linear theory, voids embedded in low (high) density regions mutually recede (attract) each other, providing the general mechanism to understand the bimodal behaviour of void motions. We have also inferred void motions in the Sloan Digital Sky Survey using linear theory, finding that their estimated motions are in qualitatively agreement with the results of the simulation. Our results suggest a scenario of galaxies and galaxy systems flowing away from void centres with the additional, and more relevant, contribution of the void bulk motion to the total velocity.
ABSTRACT
Galaxies in cosmic voids have been reported with properties related to a delayed evolution compared to the rest of the Universe. These characteristics reflect the interaction of galaxies ...with the environment. However, it is not clear the degree of influence of the large-scale structure on the properties of void galaxies or if these are only influenced by the low local density around them typical of these regions. In this article, we identified cosmic voids in the SDSS-DR16 and studied the g–r colour, star formation rate, and concentration of galaxies. We identified galaxy groups to characterize the local environment and studied the properties of galaxies as a function of total and stellar masses, separately analysing those in voids and the general sample. Our results show that galaxies that inhabit haloes of a given mass (below ${\sim}10^{13.5}{\rm M}_{\odot }$), are bluer, have a higher star formation rate and are less concentrated when the host halo is inside voids compared to other regions. For larger halo masses, the trend disappears. We also analyse whether the properties of galaxies are sensitive to the type of voids that inhabit. This is done by separating voids embedded in overdense regions (S-type) from those that asymptotically converge to the average density of the Universe (R-type). We found that galaxies in R-type voids are bluer, with higher SFR and less concentration than in S-type voids. Our results indicate some degree of correlation of galaxy properties with the large-scale environment provided by voids, suggesting possible second-order mechanisms in galaxy evolution.
Abstract
We forecast constraints on the amplitude of matter clustering
σ
8
(
z
) achievable with the combination of cluster weak lensing and number counts, in current and next-generation weak lensing ...surveys. We advocate for an approach, analogous to galaxy–galaxy lensing, in which the observables in each redshift bin are the mean number counts and the mean weak lensing profile of clusters above a mass proxy threshold. The primary astrophysical nuisance parameter is the logarithmic scatter
between the mass proxy and true mass near the threshold. For surveys similar to the Dark Energy Survey (DES), the Roman Space Telescope High Latitude Survey (HLS), and the Rubin Observatory Legacy Survey of Space and Time (LSST), we forecast aggregate precision on
σ
8
of 0.26%, 0.24%, and 0.10%, respectively,
if
the mass–observable scatter is known externally to
. These constraints would be degraded by about 20% for
in the case of DES or HLS and for
for LSST. A 1 month observing program with Roman Space Telescope targeting ∼2500 massive clusters could achieve a ∼ 0.5% constraint on
σ
8
(
z
= 0.7) on its own, or a ∼ 0.33% constraint in combination with the HLS. Realizing the constraining power of clusters Requires accurate knowledge of the mass–observable relation and stringent control of systematics. We provide analytic approximations to our numerical results that allow for easy scaling to other survey assumptions or other methods of cluster mass estimation.
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