Search for: All records

ABSTRACT Posttranslational tyrosine sulfation of peptides and proteins is catalysed by tyrosylprotein sulfotransferases (TPSTs). InArabidopsis, tyrosine sulfation is essential for the activities of peptide hormones, such as phytosulfokine (PSK) and root meristem growth factor (RGF). Here, we identified a TPST‐encoding gene,MtTPST, from model legumeMedicago truncatula.MtTPSTexpression was detected in all organs, with the highest level in root nodules. Apromoter:GUSassay revealed thatMtTPSTwas highly expressed in the root apical meristem, nodule primordium and nodule apical meristem. The loss‐of‐function mutantmttpstexhibited a stunted phenotype with short roots and reduced nodule number and size. Application of both of the sulfated peptides PSK and RGF3 partially restored the defective root length ofmttpst. The reduction in symbiotic nodulation inmttpstwas partially recovered by treatment with sulfated PSK peptide. MtTPST‐PSK module functions downstream of the Nod factor signalling to promote nodule initiation via regulating accumulation and/or signalling of cytokinin and auxin. Additionally, the small‐nodule phenotype ofmttpst, which resulted from decreased apical meristematic activity, was partially complemented by sulfated RGF3 treatment. Together, these results demonstrate that MtTPST, through its substrates PSK, RGF3 and other sulfated peptide(s), positively regulates nodule development and root growth. 

Abstract New JWST/NIRCam wide-field slitless spectroscopy provides redshifts for fourz> 8 galaxies located behind the lensing cluster MACS J0416.1−2403. Two of them, “Y1” and “JD,” have previously reported spectroscopic redshifts based on Atacama Large Millimeter/submillimeter Array measurements of [Oiii] 88μm and/or [Cii] 157.7μm lines. Y1 is a merging system of three components, and the existing redshiftz= 8.31 is confirmed. However, JD is atz= 8.34 instead of the previously claimedz= 9.28. JD’s close companion, “JD-N,” which was a previously discoveredz> 8 candidate, is now identified at the same redshift as JD. JD and JD-N form an interacting pair. A new candidate atz> 8, “f090d_018,” is also confirmed and is atz= 8.49. These four objects are likely part of an overdensity that signposts a large structure extending ∼165 kpc in projected distance and ∼48.7 Mpc in radial distance. They are magnified by less than 1 mag and have an intrinsicM_UVranging from −19.57 to −20.83 mag. Their spectral energy distributions show that the galaxies are all very young with ages ∼ 4–18 Myr and stellar masses of about 10^7–8M_⊙. These infant galaxies have very different star formation rates ranging from a few to over a hundred solar masses per year, but only two of them (JD and f090d_018) have blue rest-frame UV slopesβ< −2.0 indicative of a high Lyman-continuum photon escape fraction that could contribute significantly to the cosmic hydrogen-reionizing background. Interestingly, these two galaxies are the least massive and least active ones among the four. The other two systems have much flatter UV slopes largely because of their high dust extinction (A_V= 0.9–1.0 mag). Their much lower indicated escape fractions show that even very young, actively star-forming galaxies can have a negligible contribution to reionization when they quickly form dust throughout their bodies. 

Abstract The formation of the first supermassive black holes is expected to have occurred in some most pronounced matter and galaxy overdensities in the early universe. We have conducted a submillimeter wavelength continuum survey of 54z∼ 6 quasars using the Submillimeter Common-User Bolometre Array-2 on the James Clerk Maxwell Telescope to study the environments aroundz∼ 6 quasars. We identified 170 submillimeter galaxies (SMGs) with above 3.5σdetections in 450 or 850μm maps. Their far-IR luminosities are (2.2–6.4) × 10¹²L_⊙, and their star formation rates are ∼400–1200M_⊙yr⁻¹. We also calculated the SMGs’ differential and cumulative number counts in a combined area of ∼620 arcmin². To a 4σdetection (at ∼5.5 mJy), SMGs’ overdensity is ${0.68}_{-0.19}^{+0.21}$(±0.19), exceeding the blank-field source counts by a factor of 1.68. We find that 13/54 quasars show overdensities (at ∼5.5 mJy) ofδ_SMG∼ 1.5–5.4. The combined area of these 13 quasars exceeds the blank-field counts with the overdensity to 5.5 mJy ofδ_SMG∼ ${2.46}_{-0.55}^{+0.64}$(±0.25) in the regions of ∼150 arcmin². However, the excess is insignificant on the bright end (e.g., 7.5 mJy). We also compare results with previous environmental studies of Lyαemitters and Lyman break galaxies on a similar scale. Our survey presents the first systematic study of the environment of quasars atz∼ 6. The newly discovered SMGs provide essential candidates for follow-up spectroscopic observations to test whether they reside in the same large-scale structures as the quasars and search for protoclusters at an early epoch. 

Streams of intergalactic gas enriched by previous star formation were observed spiraling toward a massive galaxy. 

Despite renewed interest, development of chemical biology methods to study peptidoglycan metabolism has lagged in comparison to the glycobiology field in general. To address this, a panel of diamides were screened against the Gram-positive bacterium Streptococcus pneumoniae to identify inhibitors of bacterial growth. The screen identified the diamide masarimycin as a bacteriostatic inhibitor of S. pneumoniae growth with an MIC of 8 µM. The diamide inhibited detergent-induced autolysis in a concentration-dependent manner, indicating perturbation of peptidoglycan degradation as the mode-of-action. Cell based screening of masarimycin against a panel of autolysin mutants, identified a higher MIC against a Δ lytB strain lacking an endo-N-acetylglucosaminidase involved in cell division. Subsequent biochemical and phenotypic analyses suggested that the higher MIC was due to an indirect interaction with LytB. Further analysis of changes to the cell surface in masarimycin treated cells identified the overexpression of several moonlighting proteins, including elongation factor Tu which is implicated in regulating cell shape. Checkerboard assays using masarimycin in concert with additional antibiotics identified an antagonistic relationship with the cell wall targeting antibiotic fosfomycin, which further supports a cell wall mode-of-action. 

Abstract Piezoelectric polymers hold great potential for various electromechanical applications, but only show low performance, with | d 33  | < 30 pC/N. We prepare a highly piezoelectric polymer ( d 33  = −62 pC/N) based on a biaxially oriented poly(vinylidene fluoride) (BOPVDF, crystallinity = 0.52). After unidirectional poling, macroscopically aligned samples with pure β crystals are achieved, which show a high spontaneous polarization ( P s ) of 140 mC/m 2 . Given the theoretical limit of P s,β  = 188 mC/m 2 for the neat β crystal, the high P s cannot be explained by the crystalline-amorphous two-phase model (i.e., P s,β  = 270 mC/m 2 ). Instead, we deduce that a significant amount (at least 0.25) of an oriented amorphous fraction (OAF) must be present between these two phases. Experimental data suggest that the mobile OAF resulted in the negative and high d 33 for the poled BOPVDF. The plausibility of this conclusion is supported by molecular dynamics simulations. 

Abstract We report deep Karl G. Jansky Very Large Array (VLA) observations of the optically ultraluminous and radio-quiet quasar SDSS J010013.02+280225.8 (hereafter J0100+2802) at redshift z = 6.3. We detected the radio continuum emission at 1.5 GHz, 6 GHz, and 10 GHz. This leads to a radio power-law spectral index of α = −0.52 ± 0.18 ( S ∝ ν α ). The radio source is unresolved in all VLA bands with an upper limit to the size of 0.″2 (i.e., ∼1.1 kpc) at 10 GHz. We find variability in the flux density (increase by ∼33%) and the spectral index (steepened) between observations in 2016 and 2017. We also find that the VLA 1.5 GHz flux density observed in the same year is 1.5 times that detected with the Very Long Baseline Array (VLBA) in 2016 at the same frequency. This difference suggests that half of the radio emission from J0100+2802 comes from a compact core within 40 pc, and the rest comes from the surrounding few-kiloparsec area, which is diffuse and resolved out in the VLBA observations. The diffuse emission is 4 times brighter than what would be expected if driven by star formation. We conclude that the central active galactic nucleus is the dominant power engine of the radio emission in J0100+2802. 

Abstract The MAMMOTH-1 nebula at z = 2.317 is an enormous Ly α nebula (ELAN) extending to a ∼440 kpc scale at the center of the extreme galaxy overdensity BOSS 1441. In this paper, we present observations of the CO(3 − 2) and 250 GHz dust-continuum emission from MAMMOTH-1 using the IRAM NOrthern Extended Millimeter Array. Our observations show that CO(3 − 2) emission in this ELAN has not extended widespread emission into the circum- and inter-galactic media. We also find a remarkable concentration of six massive galaxies in CO(3 − 2) emission in the central ∼100 kpc region of the ELAN. Their velocity dispersions suggest a total halo mass of M 200 c ∼ 10 13.1 M ⊙ , marking a possible protocluster core associated with the ELAN. The peak position of the CO(3 − 2) line emission from the obscured AGN is consistent with the location of the intensity peak of MAMMOTH-1 in the rest-frame UV band. Its luminosity line ratio between the CO(3 − 2) and CO(1 − 0) r 3,1 is 0.61 ± 0.17. The other five galaxies have CO(3 − 2) luminosities in the range of (2.1–7.1) × 10 9 K km s −1 pc 2 , with the star-formation rates derived from the 250 GHz continuum of (<36)–224 M ⊙ yr −1 . Follow-up spectroscopic observations will further confirm more member galaxies and improve the accuracy of the halo mass estimation.