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Observations of a quasar at redshift 7.54, when the Universe was just five per cent of its current age, suggest that the Universe was significantly neutral at this epoch. A massive black hole in the early Universe Despite extensive searches, only one quasar has been known at redshifts greater than 7, at 7.09. Eduardo Bañados and colleagues report observations of a quasar at a redshift of 7.54, when the Universe was just 690 million years old, with a black-hole mass 800 million times the mass of the Sun. The spectrum shows that the quasar's Lyman α emission is being substantially absorbed by an intergalactic medium containing significantly neutral hydrogen, indicating that reionization was not complete at that epoch. Quasars are the most luminous non-transient objects known and as a result they enable studies of the Universe at the earliest cosmic epochs. Despite extensive efforts, however, the quasar ULAS J1120 + 0641 at redshift z  = 7.09 has remained the only one known at z  > 7 for more than half a decade 1 . Here we report observations of the quasar ULAS J134208.10 + 092838.61 (hereafter J1342 + 0928) at redshift z  = 7.54. This quasar has a bolometric luminosity of 4 × 10 13 times the luminosity of the Sun and a black-hole mass of 8 × 10 8 solar masses. The existence of this supermassive black hole when the Universe was only 690 million years old—just five per cent of its current age—reinforces models of early black-hole growth that allow black holes with initial masses of more than about 10 4 solar masses 2 , 3 or episodic hyper-Eddington accretion 4 , 5 . We see strong evidence of absorption of the spectrum of the quasar redwards of the Lyman α emission line (the Gunn–Peterson damping wing), as would be expected if a significant amount (more than 10 per cent) of the hydrogen in the intergalactic medium surrounding J1342 + 0928 is neutral. We derive such a significant fraction of neutral hydrogen, although the exact fraction depends on the modelling. However, even in our most conservative analysis we find a fraction of more than 0.33 (0.11) at 68 per cent (95 per cent) probability, indicating that we are probing well within the reionization epoch of the Universe.

Aluminum (Al) toxicity is a major limiting factor for plant growth and development in acidic soils. Melatonin, a plant growth regulator and signaling molecule, enhances resistance to multiple stresses. Recent studies show that melatonin alleviates Al toxicity through several complementary mechanisms. Here, we first outline the physiological and molecular impacts of Al stress and the external and internal strategies plants use to cope with it. We then summarize melatonin biosynthesis and its broader roles in stress adaptation. We focus on recent advances in melatonin-mediated mitigation of Al toxicity, highlighting four principal mechanisms: (i) the activation of antioxidant defense systems, (ii) the stimulation of organic acid anion exudation that chelates Al in the rhizosphere, (iii) the modification of cell wall composition to reduce Al binding sites, and (iv) the promotion of intracellular Al sequestration. We also discuss the crosstalk between melatonin and nitric oxide, as well as interactions with phytohormone signaling. Collectively, this review comprehensively synthesizes the current understanding regarding the role of melatonin in alleviating Al toxicity in plants, offering a promising strategy for crop production in acidic environments.

Development requires the proper execution and regulation of the cell cycle via precise, conserved mechanisms. Critically, the E2F/DP complex controls the expression of essential genes during cell cycle transitions. Here, we discovered the molecular function of the Arabidopsis thaliana SUMO E3 ligase METHYL METHANESULFONATE SENSITIVITY GENE21 (AtMMS21) in regulating the cell cycle via the E2Fa/DPa pathway. DPa was identified as an AtMMS21-interacting protein and AtMMS21 competes with E2Fa for interaction with DPa. Moreover, DPa is a substrate for SUMOylation mediated by AtMMS21, and this SUMOylation enhances the dissociation of the E2Fa/DPa complex. AtMMS21 also affects the subcellular localization of E2Fa/DPa. The E2Fa/DPa target genes are upregulated in the root of mms21-1 and mms21-1 mutants showed increased endoreplication. Overexpression of DPa affected the root development of mms21-1, and overexpression of AtMMS21 completely recovered the abnormal phenotypes of 35S:E2Fa-DPa plants. Our results suggest that AtMMS21 dissociates the E2Fa/DPa complex via competition and SUMOylation in the regulation of plant cell cycle.

Chromatin remodeling is essential for gene expression regulation in plant development and response to stresses. Brahma (BRM) is a conserved ATPase in the SWI/SNF chromatin remodeling complex and is involved in various biological processes in plant cells, but the regulation mechanism on BRM protein remains unclear. Here, we report that BRM interacts with AtMMS21, a SUMO ligase in Arabidopsis (Arabidopsis thaliana). The interaction was confirmed in different approaches in vivo and in vitro. The mutants of BRM and AtMMS21 displayed a similar defect in root development. In the mms21-1 mutant, the protein level of BRM-GFP was significantly lower than that in wild type, but the RNA level of BRM did not change. Biochemical evidence indicated that BRM was modified by SUMO3, and the reaction was enhanced by AtMMS21. Furthermore, overexpression of wild-type AtMMS21 but not the mutated AtMMS21 without SUMO ligase activity was able to recover the stability of BRM in mms21-1. Overexpression of BRM in mms21-1 partially rescued the developmental defect of roots. Taken together, these results supported that AtMMS21 regulates the protein stability of BRM in root development.

A new protocol was established for the regeneration of Solanum nigrum by frog egg-like bodies (FELBs), which are novel somatic embryogenesis (SE) structures induced from the root, stem, and leaf explants. The root, stem, and leaf explants (93.33%, 85.10%, and 100.00%, respectively) were induced to form special embryonic calli on Murashige and Skoog (MS) medium containing 1.0 mg/L 2,4-dichlorophenoxyacetic acid, under dark condition. Further, special embryonic calli from the root, stem, and leaf explants (86.97%, 83.30%, and 99.47%, respectively) were developed into FELBs. Plantlets of FELBs from the three explants were induced in vitro on MS medium supplemented with 5.0 mg/L 6-benzylaminopurine and 0.1 mg/L gibberellic acid, and 100.00% plantlet induction rates were noted. However, plantlet induction in vivo on MS medium supplemented with 20 mg/L thidiazuron showed rates of 38.63%, 15.63%, and 61.30% for the root, stem, and leaf explants, respectively, which were lower than those of the in vitro culture. Morphological and histological analyses of FELBs at different development stages revealed that they are a novel type of SE structure that developed from the mesophyll (leaf) or cortex (stem and root) cells of S. nigrum.

Observations of an ultraluminous quasar, SDSS J010013.02+280225.8, at redshift z = 6.30 show that the object has an optical and near-infrared luminosity a few times greater than those of previously known quasars at z  > 6; the black hole that drives the quasar has a mass about 12 billion times that of the Sun. Ultraluminous quasar illuminates epoch of cosmic reionization Cosmic redshifts of between 6 and 7 represent a time when the intergalactic medium was in transition from a neutral state to being completely ionized. Here Xue-Bing Wu et al . report the discovery of an ultraluminous quasar at redshift z = 6.30 that has optical and near-infrared luminosity several times greater than previously known quasars at redshifts beyond 6. Based on near-infrared spectral data, the authors estimate a mass of approximately twelve-billion solar-masses for the associated black hole, consistent with the thirteen-billion solar masses derived by assuming an Eddington-limited accretion rate, where the force of radiation acting outwards and the gravitational force acting inwards are in balance. As the most luminous quasar known to date at z = 6, this object will be a useful resource for the study of galaxy formation around massive black holes at the end of the epoch of cosmic reionization. So far, roughly 40 quasars with redshifts greater than z = 6 have been discovered 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 . Each quasar contains a black hole with a mass of about one billion solar masses (10 9 ) 2 , 6 , 7 , 9 , 10 , 11 , 12 , 13 . The existence of such black holes when the Universe was less than one billion years old presents substantial challenges to theories of the formation and growth of black holes and the coevolution of black holes and galaxies 14 . Here we report the discovery of an ultraluminous quasar, SDSS J010013.02+280225.8, at redshift z = 6.30. It has an optical and near-infrared luminosity a few times greater than those of previously known z  > 6 quasars. On the basis of the deep absorption trough 15 on the blue side of the Lyman-α emission line in the spectrum, we estimate the proper size of the ionized proximity zone associated with the quasar to be about 26 million light years, larger than found with other z  > 6.1 quasars with lower luminosities 16 . We estimate (on the basis of a near-infrared spectrum) that the black hole has a mass of ∼1.2 × 10 10 , which is consistent with the 1.3 × 10 10 derived by assuming an Eddington-limited accretion rate.

The ultraviolet broad absorption lines have been seen in the spectra of quasars at high redshift, and are generally considered to be caused by outflows with velocities from thousands kilometers per second to one tenth of the speed of light. They provide crucial implications for the cosmological structures and physical evolutions related to the feedback of active galactic nuclei（AGNs）.Recently, through a dedicated program of optically spectroscopic identifications of selected quasar candidates at redshift 5 by using the Lijiang 2.4 m telescope, we discovered two luminous broad absorption line quasars（BALQSOs） at redshift about 4.75. One of them may even have the potentially highest absorption Balnicity Index（BI） ever found to date, which is remarkably characterized by its deep, broad absorption lines and sub-relativistic outflows. Further physical properties, including the metal abundances,variabilities, evolutions of the supermassive black holes（SMBH） and accretion disks associated with the feedback process, can be investigated with multi-wavelength follow-up observations in the future.

The detection of starlight from the host galaxies of quasars during the reionization epoch ( z  > 6) has been elusive, even with deep Hubble Space Telescope observations 1 , 2 . The current highest redshift quasar host detected 3 , at z  = 4.5, required the magnifying effect of a foreground lensing galaxy. Low-luminosity quasars 4 – 6 from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) 7 mitigate the challenge of detecting their underlying, previously undetected host galaxies. Here we report rest-frame optical images and spectroscopy of two HSC-SSP quasars at z  > 6 with the JWST. Using near-infrared camera imaging at 3.6 and 1.5 μm and subtracting the light from the unresolved quasars, we find that the host galaxies are massive (stellar masses of 13 × and 3.4 × 10 10   M ☉ , respectively), compact and disc-like. Near-infrared spectroscopy at medium resolution shows stellar absorption lines in the more massive quasar, confirming the detection of the host. Velocity-broadened gas in the vicinity of these quasars enables measurements of their black hole masses (1.4 × 10 9 and 2.0 × 10 8   M ☉ , respectively). Their location in the black hole mass–stellar mass plane is consistent with the distribution at low redshift, suggesting that the relation between black holes and their host galaxies was already in place less than a billion years after the Big Bang. Images and spectroscopy obtained by the JWST from two HSC-SSP quasars show massive, compact and disc-like galaxies, indicating that the relation between black holes and their host galaxies was in place less than a billion years after the Big Bang.