APPLIED BIOLOGICAL SCIENCES
Trichonephila clavata weaving an orb web.
Mechanical properties of spider silk
A synthetic material akin to spider silk—a highly elastic structural protein with more tensile strength than steel—could be exploited across a range of industrial applications. Researchers have engineered genetically optimized organisms that artificially spin recombinant proteins into fibers, but this approach has yet to reproduce the mechanical properties of natural silks. Nobuaki Kono et al. used a multipronged approach to pinpoint the key molecular constituents of dragline silk in golden orb-weaver spiders and uncovered how each component contributes to the mechanical properties of this high-performance material. Combining high-quality genome sequencing and assembly with silk gland transcriptomics and dragline silk proteomics, the analysis revealed the presence of MaSp3B, a silk protein unique to golden orb-weaver spiders, as well as several spider-silk constituting element (SpiCE) proteins. The authors identified the function of these proteins and report that MaSp3 acts like the major ampullate proteins MaSp1 and MaSp2 and that the low-molecular-weight SpiCE proteins double the tensile strength of artificial silk in vitro. The findings suggest a strategy that can aid research on synthetic protein-based materials, according to the authors. — T.J.
NEUROSCIENCE
Female sex steroid hormones, estrogens, enhance itch in females.
Estrogens enhance female-specific itch sensitivity
Around 20% of pregnant women develop female-specific pruritus, which encompasses itchy skin conditions such as rashes, hives, eczema, and psoriasis. Although pregnancy-related itching can affect quality of life, the underlying causes are unclear. Keiko Takanami et al. investigated candidate sex hormones for female-specific itch and found that the steroid hormone estradiol, but not progesterone, mediates female itch sensitivity in rats via neurons in the spinal cord that express the gastrin-releasing peptide (GRP) receptor (GRPR). The authors report that estradiol replacement evokes and sustains itching likely by increased histamine activity, given that treatment with a receptor antagonist and a GRPR blocker attenuates the behavior. Furthermore, in vivo electrophysiological data implicated spinal GRPR-expressing neurons and increases in the frequency and duration of histamine-driven activity in the spinal dorsal horn of female rats in the underlying mechanism. Notably, progesterone treatment alone had no effect, but progesterone and estradiol together boosted GRP expression without increased itching, suggesting that progesterone may attenuate estradiol-related itch in females. The findings suggest that estrogens selectively enhance histamine-related itching by regulating spinal GRP/GRPR transcription. According to the authors, GRPR may represent a potential therapeutic target for certain types of female-specific pruritus. — T.J.
ANTHROPOLOGY
Skull of the Dead Sea crested rat subspecies found in the Cave of the Skulls in the southern Judean Desert.
Levantine crested rat and early human dispersals
Early humans and other hominins dispersed out of Africa through the Levant multiple times, but whether these journeys relied on technology to cross the Saharo-Arabian deserts or followed ecological corridors created by climate change is unclear. Ignacio Lazagabaster et al. analyzed rodent fossils discovered in the Cave of the Skulls in the southern Judean Desert as a proxy for the paleoenvironment of the Dead Sea region during the Late Pleistocene. Phylogenetic analyses of a sequenced mitochondrial genome and morphological comparisons suggest that the fossils, which were dated to between 42,000 and more than 103,000 years ago, belong to a now-extinct subspecies, Lophiomys imhausi maremortum subsp. nov., of the Eastern African crested rat, an enigmatic large rodent equipped with a poisonous pelt and a helmet-like skull. Because extant crested rats live in habitats with relatively dense vegetation, the authors used species distribution models to estimate the timing and location of previously suitable habitats in the region. The results suggest a brief period during the Last Interglacial when green habitat corridors connected Eastern Africa to the Levant across the present-day Judean Desert, facilitating the dispersal of crested rats and humans out of Africa, according to the authors. — M.H.
PSYCHOLOGICAL AND COGNITIVE SCIENCES
Education and intergenerational disadvantages
Health and living standards are improving across the Western world. However, not all individuals have benefited equally from such improvements, potentially due to disadvantages persisting within families across generations, among other factors. Signe Hald Andersen, Leah Richmond-Rakerd, et al. examined public service–use records for 636,385 Danish citizens who were born in Denmark between 1974 and 1984. Individuals’ records were compared with records of their parents and children, and the authors examined use of public services related to physical health, mental health, social welfare, criminal offenses, and protective services. Individuals who disproportionately used multiple health and social services often had parents who also disproportionately used multiple health and social services. Such individuals also tended to have children who appeared in records related to protective services, suggesting increased risk of becoming disadvantaged adults. Compared with their siblings who obtained less education, individuals who completed more schooling exhibited reduced risk of disadvantages later in life, even if they had disadvantaged parents. The findings suggest that increasing investment in education, especially for underserved populations, may reduce inequality by interrupting the intergenerational cycle of disadvantage, according to the authors. — M.S.
ECOLOGY
Adult female northern spotted owl (Strix occidentalis caurina) in the Coast Range of western Oregon. Image credit: Patrick S. Kolar (US Geological Survey, Washington, DC).
Controlling invasive barred owl populations
Removing invasive species to decrease the risk of extinction of native species is common, but the long-term effects of such ecological restoration programs are unclear. Native to eastern North America, barred owls are considered an invasive species on the western coast of the United States, and their territorial competition with the region’s northern spotted owls has led to the latter’s population decline. Between 2002 and 2019, J. David Wiens et al. surveyed barred owls and spotted owls across five study areas in California, Oregon, and Washington. The authors compared owl populations before and after invasive barred owls underwent removal treatments. Removal of barred owls had a significant positive effect on the survival of spotted owls, having arrested spotted owl population declines. The authors also detected an increase in spotted owls dispersing to territories upon barred owl removal from such locations. However, spotted owl populations continued declining rapidly in areas where barred owls did not undergo removal treatments. The findings suggest that controlling invasive barred owl populations may not only increase native spotted owl populations but also help to conserve biodiversity across the Pacific Northwest, according to the authors. — M.S.
ECOLOGY
Honeycomb.
Comb construction in honey bees
Honey bees construct perfectly hexagonal honeycombs but may encounter obstacles in achieving this architecture. Using automated image analysis of naturally built honeycombs, Michael Smith et al. examined building challenges that bees face during nest construction as well as the methods bees use to solve such challenges. The authors analyzed more than 19,000 individual comb cells built by 12 colonies. Worker bees preemptively changed their building behavior to create space for large hexagonal cells, built irregular cell shapes arranged in patterns, and changed both the tilt, size, and number of walls to overcome various building challenges. Challenges arise naturally in colonies, such as when workers transition from building small hexagons to large hexagons or when bees must merge two independent pieces of comb together. The authors report that some comb-building challenges were exceptionally difficult for bees, such as merging combs with unaligned cells. When minor adjustments proved unsuccessful, workers constructed pairs and triplets of nonhexagonal cells, while conserving wax. The findings contradict the view of honey bees as comb-building automatons and instead suggest that the insects are skilled architects, according to the authors. — M.S.
CELL BIOLOGY
When Arabidopsis seeds—like those in these seed pods captured with a colored scanning electron micrograph—were exposed to water, proteins called FLOE1 rapidly condensed to form blobs, essentially acting as water sensors. Such protein characteristics are reminiscent of prions. Image credit: Science Source/Dennis Kunkel.
Prion-like protein acts as water sensor in seeds
Posted on July 26, 2021
Jyoti Madhusoodanan
The sprouting of a seed is clearly a crucial stage in a plant’s life. Yet one part of the process has long been shrouded in mystery: How do seeds know when there’s enough water to germinate?