Rhamnose is an essential component of the plant cell wall and is synthesized from uridine diphosphate (UDP)-glucose by the RHAMNOSE1 (RHM1) enzyme. RHM1 localizes to biomolecular condensates in plants, but their identity, formation, and function remain elusive. Combining live imaging, genetics, and biochemical approaches in Arabidopsis and heterologous systems, we show that RHM1 alone is sufficient to form enzymatically active condensates, which we name ‘rhamnosomes’. Rhamnosome formation is required for UDP-rhamnose synthesis and organ development. Overall, our study demonstrates a novel role for biomolecular condensation in metabolism and organismal development, and provides further support for how organisms have harnessed this biophysical process to regulate small molecule metabolism.

Noninvasive phenotyping can quantify dynamic plant growth processes at higher temporal resolution than destructive phenotyping and can reveal phenomena that would be missed by end-point analysis alone. Additionally, whole-plant phenotyping can identify growth conditions that are optimal for both above- and below-ground tissues. However, noninvasive, whole-plant phenotyping approaches available today are generally expensive, complex, and non-modular. We developed a low-cost and versatile approach to noninvasively measure whole-plant physiology over time by growing plants in isolated hydroponic chambers. We demonstrate the versatility of our approach by measuring whole-plant biomass accumulation, water use, and water use efficiency every two days on unstressed and osmotically stressed sorghum accessions. We identified relationships between root zone acidification and photosynthesis on whole-plant water use efficiency over time. Our system can be implemented using cheap, basic components, requires no specific technical expertise, and should be suitable for any non-aquatic vascular plant species.

We find that Large Igneous Province (LIP) volcanism, mostly continental flood basalts (CFBs), along with the largest extraterrestrial impacts show significant correlations with mass -extinction events in the Phanerozoic geologic record. The ages of the 6 major marine mass extinctions (>= 40% extinction of genera) of the last 541 My-the end -Ordovician (-444 Ma), late Devonian (-372 Ma), end-Guadalupian (-259 Ma), end -Permian (-252 Ma), end -Triassic (-201 Ma), and end -Cretaceous (66 Ma) extinctions are significantly correlated with high -quality U-Pb zircon and 40Ar/39Ar ages of 6 continental flood basalts (CFBs) -the Cape St. Mary's, Viluy, Emeishan, Siberian, CAMP, and the Deccan Basalts, The mass extinctions also coincide with stratigraphic Hg anomalies representing proxy evidence for the synchrony of the extinctions and the basaltic volcanism. Furthermore, ages of 6 minor extinction events (15% to 25% extinction of marine genera) at - 94 Ma, 124 Ma, 134 Ma, 183 Ma, 290 Ma and 510 Ma also coincided with 6 well -dated CFB eruptions (the Madagascar, HALIP, Parana/Etendeka, Karoo/Ferrar, Panjal and Kakarindji Basalts) and with associated Hg anomalies. At least 3 minor extinction events (at - 145 Ma, 215 Ma and 227 Ma) apparently occurred close to times of oceanic plateau (OP) volcanism in the Pacific Ocean (Shatsky Rise, Angayucham and Wrangellia Basalts). Major and minor marine mass -extinction episodes at times of CFB eruptions were commonly accompanied by ocean anoxic/euxinic events, increased ocean acidity, high atmospheric pCO2, increases in UV -B radiation from ozone -layer destruction, and pulses of high ambient temperatures, providing potential immediate causes for the mass extinctions. The 4 most recent major marine extinctions (-66 Ma, 201 Ma, 252 Ma, and 260 Ma) and a minor extinction (-290 Ma) coincided with the ages of CFBs and with concurrent mass extinctions of non -marine vertebrates, indicating global -scale volcanogenic environmental crises on land and in the sea. The age of the abrupt end -Cretaceous major mass extinction (66 Ma) overlaps with the age of the Deccan eruptions, but is exactly coincident with the very large Chicxulub impact (180 km diameter crater), possibly the largest terrestrial impact of the last -3 By. The ages of the 3 next largest well -dated Phanerozoic terrestrial impact craters (>= 100 km in diameter), the Popigai, Morokweng and Manicouagan craters, capable of causing widespread environmental effects, are concurrent with the ages of minor extinction events at -37 Ma, 145 Ma and 215 Ma. The significant correlations and the predicted severe environmental consequences of these major volcanic and impact events are very convincing that 12 CFB eruptions, at least 3 oceanic plateau eruptions, and the 4 largest impacts were involved with recognized biotic mass -extinction episodes of the last 541 My, and leave little room for alternate primary causes of the extinctions.

Wind droughts, or prolonged periods of low wind speeds, pose challenges for electricity systems largely reliant on wind generation. Using weather reanalysis data, we analyzed the global distribution of and trends in wind droughts using an energy deficit metric that integrates the depth and duration of wind droughts. We identified regions with high power densities, low seasonal variability, and limited weather fluctuations that favor wind power generation, such as the American Midwest, Australia, the Sahara, Argentina, Central Asia, and Southern Africa. Northwestern Europe has high power densities but experiences more frequent and prolonged wind droughts due to higher weather variability. We found little evidence for strong trends in wind droughts over recent decades in most places. Rather, the most severe wind droughts in many places occurred before wind power substantially penetrated power systems, which suggests that historical weather data can be useful in designing reliable wind-reliant electricity systems.

Skeletal muscles connect bones and tendons for locomotion and posture. Understanding the regenerative processes of muscle, bone and tendon is of importance to basic research and clinical applications. Despite their interconnections, distinct transcription factors have been reported to orchestrate each tissue developmental and regenerative processes. Here we show that Scx expression is not detectable in adult muscle stem cells (also known as satellite cells, SCs) during quiescence. Scx expression begins in activated SCs and continues throughout regenerative myogenesis after injury. By SC-specific Scx gene inactivation (ScxcKO), we show that Scx function is required for SC expansion/renewal and robust new myofiber formation after injury. We combined single-cell RNA-sequencing and CUT&RUN to identify direct Scx target genes during muscle regeneration. These target genes help explain the muscle regeneration defects of ScxcKO, and are not overlapping with Scx-target genes identified in tendon development. Together with a recent finding of a subpopulation of Scx-expressing connective tissue fibroblasts with myogenic potential during early embryogenesis, we propose that regenerative and developmental myogenesis co-opt the Scx gene via different mechanisms.

Peripheral neurons terminate at the surface of tendons partly to relay nociceptive pain signals; however, the role of peripheral nerves in tendon injury and repair remains unclear. Here, we show that after Achilles tendon injury in mice, there is new nerve growth near tendon cells that express nerve growth factor (NGF). Conditional deletion of the Ngf gene in either myeloid or mesenchymal mouse cells limited both innervation and tendon repair. Similarly, inhibition of the NGF receptor tropomyosin receptor kinase A (TrkA) abrogated tendon healing in mouse tendon injury. Sural nerve transection blocked the postinjury increase in tendon sensory innervation and the expansion of tendon sheath progenitor cells (TSPCs) expressing tubulin polymerization promoting protein family member 3. Single cell and spatial transcriptomics revealed that disruption of sensory innervation resulted in dysregulated inflammatory signaling and transforming growth factor-beta (TGF beta) signaling in injured mouse tendon. Culture of mouse TSPCs with conditioned medium from dorsal root ganglia neuron further supported a role for neuronal mediators and TGF beta signaling in TSPC proliferation. Transcriptomic and histologic analyses of injured human tendon biopsy samples supported a role for innervation and TGF beta signaling in human tendon regeneration. Last, treating mice after tendon injury systemically with a small-molecule partial agonist of TrkA increased neurovascular response, TGF beta signaling, TSPC expansion, and tendon tissue repair. Although further studies should investigate the potential effects of denervation on mechanical loading of tendon, our results suggest that peripheral innervation is critical for the regenerative response after acute tendon injury.

Coral growth depends on the partnership between the animal hosts and their intracellular, photosynthetic dinoflagellate symbionts. In this study, we used the sea anemone Aiptasia, a laboratory model for coral biology, to investigate the poorly understood mechanisms that mediate symbiosis establishment and maintenance. We found that initial colonization of both adult polyps and larvae by a compatible algal strain was more effective when the algae were able to photosynthesize and that the long-term maintenance of the symbiosis also depended on photosynthesis. In the dark, algal cells were taken up into host gastrodermal cells and not rapidly expelled, but they seemed unable to reproduce and thus were gradually lost. When we used confocal microscopy to examine the interaction of larvae with two algal strains that cannot establish stable symbioses with Aiptasia, it appeared that both pre- and post-phagocytosis mechanisms were involved. With one strain, algae entered the gastric cavity but appeared to be completely excluded from the gastrodermal cells. With the other strain, small numbers of algae entered the gastrodermal cells but appeared unable to proliferate there and were slowly lost upon further incubation. We also asked if the exclusion of either incompatible strain could result simply from their cells' being too large for the host cells to accommodate. However, the size distributions of the compatible and incompatible strains overlapped extensively. Moreover, examination of macerates confirmed earlier reports that individual gastrodermal cells could expand to accommodate multiple algal cells.This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

The symbioses between leguminous plants and nitrogen-fixing bacteria known as rhizobia are well known for promoting plant growth and sustainably increasing soil nitrogen. Recent evidence indicates that hopanoids, a family of steroid-like lipids, promote Bradyrhizobium symbioses with tropical legumes. To characterize hopanoids in Bradyrhizobium symbiosis with soybean, we validated a recently published cumate-inducible hopanoid mutant of Bradyrhizobium diazoefficiens USDA110, Pcu-shc:: increment shc. GC-MS analysis showed that this strain does not produce hopanoids without cumate induction, and under this condition, is impaired in growth in rich medium and under osmotic, temperature, and pH stress. In planta, Pcu-shc:: increment shc is an inefficient soybean symbiont with significantly lower rates of nitrogen fixation and low survival within the host tissue. RNA-seq revealed that hopanoid loss reduces the expression of flagellar motility and chemotaxis-related genes, further confirmed by swim plate assays, and enhances the expression of genes related to nitrogen metabolism and protein secretion. These results suggest that hopanoids provide a significant fitness advantage to B. diazoefficiens in legume hosts and provide a foundation for future mechanistic studies of hopanoid function in protein secretion and motility. IMPORTANCE A major problem for global sustainability is feeding our exponentially growing human population while available arable land decreases. Harnessing the power of plant-beneficial microbes is a potential solution, including increasing our reliance on the symbioses of leguminous plants and nitrogen-fixing rhizobia. This study examines the role of hopanoid lipids in the symbiosis between Bradyrhizobium diazoefficiens USDA110, an important commercial inoculant strain, and its economically significant host soybean. Our research extends our knowledge of the functions of bacterial lipids in symbiosis to an agricultural context, which may one day help improve the practical applications of plant-beneficial microbes in agriculture.

The potential of enhanced agricultural management practices to drive sustainability is rarely quantified at grassroots level. Here we analyse nitrogen use and loss in Chinese cropland, drawing from data collected in 2,238,550 sites in two national agricultural pollution source censuses from 2007 to 2017. We find an upswing of 10% in crop yields and an 8% reduction in nitrogen pollution during this period, owing to the promotion and adoption of various management practices (including the combination of organic and chemical fertilizers, straw recycling and deep placement of fertilizer). These practices have collectively contributed to an 18% increase in nitrogen use efficiency in the country. By fully embracing them, we project that annual cropland pollution could be further reduced by up to 1.4Mt of nitrogen without compromising crop yields. Environmental and human health benefits are projected to consistently outweigh implementation costs in the future, with total benefits reaching US$15 billion.