Phylogenetically guided drug discovery
Species-rich rainforests of Mount Halimun Salak National Park, Java, Indonesia.
Multidrug-resistant bacteria have emerged as a major global public health threat resulting from high antibiotic use in healthcare and livestock, prompting the need to identify new antibiotics. Laura Holzmeyer, Anne-Kathrin Hartig, Jan Schnitzler, et al. (pp. 12444–12451) developed a method to search for potential antiinfective lead compounds in plants by integrating phylogenetic, spatial, and bioactivity data. As a test case, the authors examined more than 16,000 secondary metabolites found in more than 7,500 seed plant species on the Indonesian island of Java. The authors identified 26 plant clades in which antiinfective activities were overrepresented and therefore have a high probability of yielding bioactive compounds. The authors also identified 24 clades in which such activities were underrepresented. The clades have an overall low probability of yielding antiinfectives, but any antiinfective found has a high probability of being a novel type of antiinfective. Comparison of the geographic distributions of plant species and plant metabolites revealed a strong correlation between species diversity and metabolite diversity, reinforcing the importance of conserving biodiversity hotspots. The approach could help guide the search for novel antiinfective compounds by identifying promising taxa and geographic areas, according to the authors. — B.D.
Plant strengthener impedes insect feeding
Deposition of phenolic polymers in rice cells 0 (Left) and 4.5 days (Right) after 4-FPA treatment.
One strategy for protecting food crops uses plant strengtheners, which are chemicals that elicit plants’ stress-related defense mechanisms to bolster resistance to herbivore pests. Although promising, little is known about the chemicals’ method of action, and few studies have tested strengtheners in the field because of potential side effects on plant growth and yield. Wanwan Wang et al. (pp. 12017–12028) used a high-throughput screening system to identify the plant strengthener candidate 4-fluorophenoxyacetic acid (4-FPA), a chemical analog of a herbicide that induces rice plants to repel white-backed plant hopper (WBPH) nymphs. The authors combined molecular and chemical analyses with laboratory and field studies to show how 4-FPA–treated cereals resist piercing and sucking insect pests. Instead of activating defense signaling pathways, 4-FPA triggers a chemical cascade that deposits phenolic polymers directly into parenchyma cells in rice, wheat, and barley. The polymer influx reinforces the plant cells, creating a physical barrier to WBPH stylet penetration, thus protecting the plant and increasing crop yield. The findings describe a plant resistance mechanism that can be used to design eco-friendly plant strengtheners, according to the authors. — T.J.
Flying insects use cues to navigate toward virtual objects
Tethered apple fly (Rhagoletis pomonella) approaching a tree-like virtual object in a multimodal virtual reality arena.
Flying insects are remarkable for their ability to rapidly locate objects such as food and mates while exploring a complex 3D world. However, how insects accomplish this computationally intensive feat during flight, especially over large spatial scales, is unclear. Pavan Kaushik et al. (pp. 12201–12207) used virtual reality to examine the behavior of tethered flying insects, including apple flies, mosquitoes, hoverflies, and crane flies. The virtual reality arena consisted of complex 3D visual scenery with grass, sky, trees, and flowers, as well as odors and wind tunnel-like airflow fields. All four Dipteran species located and approached flowers or trees, which are preferred sites for mating, feeding, or egg-laying in the real world. In addition, apple flies were more likely to approach close trees than faraway trees, suggesting that the flies use depth cues such as perspective and motion parallax to determine virtual object distance. Moreover, apple flies combined directional airflow and odor information to locate and move toward virtual fruit-blend odor plumes. Taken together, the findings demonstrate that flying insects integrate multiple types of sensory cues to locate and navigate toward virtual objects in a complex 3D landscape. According to the authors, the findings could be used to optimize strategies for pest control, crop pollination, and disease vector management. — J.W.
Trends in tropical cyclone intensity
Hurricanes Katia (Left), Irma (Center), and Jose (Right) over Mexico and the Caribbean on September 8, 2017. Image credit: Wikimedia Commons/NOAA View Global Data Explorer.
Theory and models suggest that tropical cyclone (TC) intensity tends to increase with global mean surface temperatures. However, such a trend is difficult to detect in observations because of spatial and temporal heterogeneities in the instrumental record. To increase the confidence in the trend extracted from observations, James Kossin et al. (pp. 11975–11980) extended an existing globally homogenized record of satellite imagery to encompass the period 1979–2017. The record had previously covered the years 1982–2009 and exhibited increasing trends in global TC intensity, but the trends were not statistically significant. The authors found that the probability of a hurricane having wind speeds of at least 100 knots increased by approximately 15% between the early and latter halves of the 39-year record. This finding corresponds to a statistically significant rate of increase of approximately 8% per decade. A time series of the proportion of all hurricanes exceeding 100 knots exhibited a similar increasing trend of approximately 6% per decade. The results are consistent with the predictions of physical theory and numerical simulations and increase confidence in the view that TCs have become stronger under global warming, according to the authors. — B.D.