Known as the 'ultimate semiconductor', cubic diamond (CD) has gained substantial interest both scientifically and industrially. Its polymorph, hexagonal diamond (HD), is even more intriguing because of its fascinating properties associated with the meteorite impacts1-8. As no solid experimental evidence has been provided to prove its existence, the physical properties of HD remain largely unexplored. Here we report the synthesis of millimetre-sized, phase-pure HD from highly oriented pyrolytic graphite (HOPG) compressed along the c-axis at elevated temperatures. Combining advanced structural characterizations and theoretical simulations, we confirm the identity of HD and clarify the transformation pathway from graphite. Bulk HD exhibits a slightly higher hardness than CD and high thermal stability. These findings resolve the long-standing controversy on the existence of HD as a discrete carbon phase and provide new insight into the graphite-to-diamond phase transition, paving the way for future research and practical use of HD in advanced technological applications.

Influenza virus mRNAs are stable and competent for nuclear export and translation because they receive a 5' cap(1) structure in a process called cap snatching1. During cap snatching, the viral RNA-dependent RNA polymerase (FluPol) binds to host RNA polymerase II (Pol II) and the emerging transcript2,3. The FluPol endonuclease then cleaves a capped RNA fragment that subsequently acts as a primer for the transcription of viral genes4,5. Here we present the cryogenic electron microscopy structure of FluPol bound to a transcribing Pol II in complex with the elongation factor DSIF in the pre-cleavage state. The structure shows that FluPol directly interacts with both Pol II and DSIF, positioning the FluPol endonuclease domain near the RNA exit channel of Pol II. These interactions are important for the endonuclease activity of FluPol and FluPol activity in cells. A second structure, trapped after cap snatching, shows that the cleaved capped RNA rearranges within FluPol, directing the capped RNA 3' end toward the FluPol polymerase active site for viral transcription initiation. Together, our results provide the molecular mechanisms of co-transcriptional cap snatching by FluPol.

Rivers are Earth's most renewable and accessible freshwater resource1, yet global estimates of the magnitude and variability in river water storage have remained few and inconsistent1-9. Previous estimates of variability have relied either on sparse and asynchronous remote-sensing observations10 or on hydrological models constrained by incomplete understanding of surface-water balance and poorly known river channel characteristics2,3. The insufficient knowledge of temporal variations in river water storage across space hinders effective management of this critical freshwater resource11,12. Here we present near-global-scale observations of active river channel geometry and associated monthly changes in water storage at the reach scale derived from the first water year (October 2023 to September 2024) of the Surface Water and Ocean Topography (SWOT) mission at 126,674 reaches worldwide. Clear patterns of riverbed shape and storage variability expectedly emerge across major basins. SWOT reveals a range of 313.1 ± 129.5 km³ in global annual river storage variability, approximately 28% lower than the lowest previously modelled estimates for the same wide reaches. Although the Amazon's 2024 record drought, the observational challenges in the Arctic and the revisit frequency of SWOT almost certainly contribute to the discrepancy, the observations point to distinct knowledge limitations in surface-water science. These findings highlight key opportunities to improve the fundamental representation of surface-water dynamics in global models and to better inform water resource management and disaster mitigation at scale.

Interactions between mutant cells and their environment have a key role in determining cancer susceptibility1-3. However, understanding of how the precancerous microenvironment contributes to early tumorigenesis remains limited. Here we show that newly emerging tumours at their most incipient stages shape their microenvironment in a critical process that determines their survival. Analysis of nascent squamous tumours in the upper gastrointestinal tract of the mouse reveals that the stress response of early tumour cells instructs the underlying mesenchyme to form a supportive 'precancerous niche', which dictates the long-term outcome of epithelial lesions. Stimulated fibroblasts beneath emerging tumours activate a wound-healing response that triggers a marked remodelling of the underlying extracellular matrix, resulting in the formation of a fibronectin-rich stromal scaffold that promotes tumour growth. Functional heterotypic 3D culture assays and in vivo grafting experiments, combining carcinogen-free healthy epithelium and tumour-derived stroma, demonstrate that the precancerous niche alone is sufficient to confer tumour properties to normal epithelial cells. We propose a model in which both mutations and the stromal response to genetic stress together define the likelihood of early tumours to persist and progress towards more advanced disease stages.

In both natural and engineered biological systems, RNA-guided proteins have emerged as critical transcriptional regulators by modulating RNA polymerase (RNAP) and its associated factors1-3. In bacteria, diverse clades of repurposed TnpB and CRISPR-associated proteins repress gene expression by blocking transcription initiation or elongation, enabling non-canonical modes of regulatory control and adaptive immunity1,4,5. A distinct class of nuclease-dead Cas12f homologues (dCas12f) instead activates gene expression through its association with unique extracytoplasmic function sigma factors (σE)6, although the molecular basis has remained elusive. Here we reveal a new mode of RNA-guided transcription initiation by determining the cryo-electron microscopy structures of the dCas12f-σE system from Flagellimonas taeanensis. We captured multiple conformational and compositional states, including the DNA-bound dCas12f-σE-RNAP holoenzyme complex, revealing how RNA-guided DNA binding leads to σE-RNAP recruitment and nascent mRNA synthesis at a precisely defined distance downstream of the R-loop. Rather than following the classical paradigm of σE-dependent promoter recognition, these studies show that recognition of the -35 element is largely supplanted by CRISPR-Cas targeting, whereas the melted -10 element is stabilized through unusual stacking interactions rather than insertion into the typical recognition pocket. Collectively, this work provides high-resolution insights into an unexpected mechanism of RNA-guided transcription, expanding our understanding of bacterial gene regulation and opening new avenues for programmable transcriptional control.

Insects make up the majority of all animal species, with 70% occurring in the tropics1, yet the impacts of warming on tropical insects remain highly uncertain2. This stems from sparse, taxonomically biased data on thermal tolerance of tropical insects and an incomplete understanding of the underlying physiological mechanisms3. Here we compared environmental temperatures with field-measured upper and lower thermal tolerance limits of around 2,300 insect species along Afrotropical and Neotropical elevational gradients and identified genomic signatures of thermal tolerance across the insect tree of life. We show that thermal tolerances do not proportionally track environmental temperatures but approach an asymptote in tropical lowlands. Insects at high elevations utilize plasticity to cope with rising temperatures, whereas lowland species have limited plastic abilities. Heat tolerance showed strong differences among insect orders and families, reflected in the thermal stability of proteins, suggesting that variation in thermal tolerance is founded in the fundamental protein architecture. Up to 52% of future surface temperatures and 38% of air temperatures in the Amazonian lowlands can cause heat mortality in half of the studied community. Our data suggest a limited capacity of insects in the Earth's most biodiverse regions to buffer future warming.