American Scientist

In this roundup, managing editor Stacey Lutkoski summarizes notable recent developments in scientific research, selected from reports compiled in the free electronic newsletter Sigma Xi SmartBrief.

Exoplanet Moon Creation

For the first time, astronomers have found convincing evidence of a moon forming in a disc of dust around a newborn planet. Astronomers have theorized that moons originate in such discs, much as planets form in the larger discs around young stars, but nobody had seen the process in action. Researchers using the European Southern Observatory’s Very Large Telescope in Chile had previously detected two protoplanets (planets in the process of formation) in the PDS 70 star system, which is 370 light-years away and just 5 million years old—a stellar infant. Both protoplanets are gas giants several times more massive than Jupiter. A team led by Myriam Benisty of the University of Grenoble used the Atacama Large Millimeter/submillimeter Array (ALMA, a collection of radio dishes in Chile) to zero in on the star system and found a dusty disc surrounding one of the protoplanets, PDS 70c; such a protoplanetary disc had never been observed clearly before. Some moons may have already begun forming around PDS 70c, but if so, they are too small for us to see. Observing the development of this young star system and its planets will help astronomers understand how our Solar System—in particular, the moon systems of Jupiter, Saturn, and Uranus—was formed.

Benisty, M., et al. A circumplanetary disk around PDS70c. Astrophysical Journal Letters doi:10.3847/2041-8213/ac0f83 (July 22).

Noninvasive Cancer Diagnosis

Medical engineers have created a nanoparticle that can help oncologists detect cancer through a simple urine test; the test can also identify the organs affected. The key to this development is a nanosensor that is delivered to a patient intravenously. As it passes through the body, the nanosensor reacts to proteases (enzymes that break down proteins) in malignant tumors, and biomarkers from that interaction are evident in the patient’s urine. The particle is attracted to the acidic environment common among cancerous tumors, and it contains radioactive copper-64, which shows up in positron emission tomography (PET) imaging. If a urine test indicates that the nanosensor has encountered cancer in the body, a subsequent PET scan can locate where the nanoparticles are collecting to pinpoint the tumor’s location. In mouse models, these tests successfully identified metastatic colon cancer and were able to track how the mice responded to chemotherapy treatments. This method would provide a less invasive way to diagnose cancer and could help with early detection of the disease.

Hao, L., et al. Microenvironment-triggered multimodal precision diagnostics. Nature Materials doi:10.1038/s41563-021-01042-y (July 15).

Cooperative Plants

An Australasian fern species may engage in division of labor in much the same way that some insects, such as ants and bees, separate tasks within their colonies. This type of division of labor by caste within a species is called eusociality. In addition to insects, it has been documented in crustaceans and two mole rat species, but until now the behavior had not been observed in plants. The fern, Platycerium bifurcatum, is an epiphyte, which means it grows on other plants but derives its nutrients from the air and rain (unlike a parasite, which draws nutrients from its host). Biologist Kevin Burns of Victoria University in New Zealand noticed that the plant grows in colonies of about 25 individuals and that they produce two types of fronds, which he calls strap fronds and nest fronds. The green strap fronds grow like long, thin leaves outward from the nest fronds, which are brown and anchored to the plant host. Burns and colleagues found that about 60 percent of the strap fronds they studied were reproductively active, whereas the remaining strap fronds and all nest fronds were reproductively inactive; this division of reproductive labor is a hallmark of eusociality. The outer nest fronds are large and waxy, and they shunt water to smaller, hydrophilic nest fronds in the interior. A root system then distributes the collected water throughout the colony. The identification of a eusocial plant challenges previous assumptions that this type of behavioral coordination requires a brain, and it raises the possibility of convergent evolution of that characteristic in plants and animals.

Burns, K. C., I. Hutton, and L. Shepherd. Primitive eusociality in a land plant? Ecology doi:10.1002/ecy.3373 (May 14).

Reviving Pleistocene Life

A multicellular organism that was trapped in permafrost for approximately 24,000 years is still alive. Lyubov Shmakova of the Soil Cryology Laboratory at the Pushchino Scientific Center for Biological Research in Russia and her colleagues thawed a bdelloid rotifer—a ubiquitous microscopic creature known to withstand extreme cold—from a sample collected in northeastern Siberia. The researchers radiocarbon-dated microbes that were frozen alongside the rotifer, which allowed them to estimate its age. Once it had been defrosted, the rotifer was able to reproduce asexually, which means that its DNA and other critical biomarkers remained intact after all those years. In 2018, another team successfully revived a 30,000-year-old nematode. These resilient multicellular organisms provide opportunities to study the biomechanics necessary to survive in low temperatures, which could lead to advances in cryobiology and biotechnology.

Shmakova, L., et al. A living bdelloid rotifer from 24,000-year-old Arctic permafrost. Current Biology doi:10.1016/j.cub.2021.04.077 (June 7).