Letters in 2014

Carbon dioxide and carbon monoxide measurements across the Amazon basin for 2010 and 2011 reveal that drought rather than temperature caused the observed halt in forest productivity during the anomalously dry year of 2010.

Marine protected areas (MPAs) are an important and increasing component of marine conservation strategy, but their effectiveness is variable and debated; now a study has assembled data from a global sample of MPAs and demonstrates that effectiveness depends on five key properties: whether any fishing is allowed, enforcement levels, age, size and degree of isolation.

The unusual structures of quasicrystals, such as the 18-fold symmetry observed in polymer micelles, lack the repeating cell pattern of conventional hard crystals; here their origin is shown to be an extension of Penrose tiling with a simple, generic interparticle interaction.

The AgRP-expressing neurons in the arcuate nucleus drive food-seeking behaviours during caloric restriction; a mouse study of monosynaptic retrograde rabies spread and optogenetic circuit mapping reveals that these neurons are activated by input from hypothalamic paraventricular nucleus cells and their activation or inhibition can modulate feeding behaviour.

Here it is shown that T-cell receptors accumulate at the immunological synapse after stimulation with cognate antigen and are released in extracellular microvesicles by an ESCRT-dependent mechanism, the microvesicles deliver transcellular signals from CD4 T cells to antigen-presenting B cells and can induce B-cell signalling.

A tropical cyclone activity index that allows for a direct comparison between the modern instrumental record and long-term palaeotempest (prehistoric tropical cyclone) records shows that present low levels of storm activity on the mid west and northeast coasts of Australia are unprecedented over the past 550 to 1,500 years.

An RNA secondary structure (RSS) map of coding and noncoding RNA from a human family (two parents and their child) is produced; this reveals that approximately 15% of all transcribed single nucleotide variants (SNVs) alter local RNA structure, and these SNVs are depleted in certain locations, suggesting that particular RNA structures are important at those sites.

Dirac magnetic monopoles are created, directly imaged and identified in real space in the synthetic magnetic field produced by a spinor Bose–Einstein condensate.

A map of the surface of a brown dwarf reveals features that suggest patchy clouds, providing the mechanism for the dispersal of atmospheric dust as brown dwarfs cool with age.

In the modern human genome, elevated Neanderthal ancestry is found at genes affecting keratin filaments, suggesting that gene flow with Neanderthals helped modern humans to adapt to non-African environments; deficiencies of Neanderthal ancestry are also found, particularly on the X chromosome and in genes expressed highly in testes, suggesting that some Neanderthal mutations were not tolerated on a modern human genetic background as they reduced male fertility.

One of two papers describing a reprogramming phenomenon called stimulus-triggered acquisition of pluripotency (STAP) — in STAP, lineage-committed adult somatic cells are reprogrammed to pluripotency by transient exposure to low-pH treatment, and extensive analysis of the molecular features and developmental potential of STAP cells indicates that they represent a unique state of pluripotency.

A complete pre-agricultural European human genome from a ∼7,000-year-old Mesolithic skeleton suggests the existence of a common genomic signature across western and central Eurasia from the Upper Paleolithic to the Mesolithic, and ancestral alleles in several skin pigmentation genes suggest that the light skin of modern Europeans was not yet ubiquitous in Mesolithic times.

The long-term record of atmospheric carbon dioxide growth rate shows that the sensitivity of this growth rate to tropical temperature variability has increased by a factor of about two in the past five decades, and was greater when tropical land regions experienced drier conditions, implying that moisture regulates this sensitivity.

Escherichia coli K-12 performs sulphoglycolysis; heterologous expression of enzymes encoded in a ten-gene cluster present in almost all (>91%) available E. coli genomes is used to show that sulphoquinovose is catabolised through four reactions to produce dihydroxyacetone phosphate, which powers energy conservation and growth, and a sulphonate product, which is excreted.

This study shows that PADI4-mediated citrullination occurs during pluripotency and that citrullination of H1 results in loosening of chromatin compaction; furthermore, citrullination is shown to be important for the activation of stem-cell genes, for iPS cell reprogramming and to maintain pluripotent cells in the early mouse embryo.

The largest asteroid of the Solar System, (1) Ceres, has been thought to have an icy surface; here it is observed to be emitting water vapour.

Suppressing fungi in a tropical forest plant community lowers diversity by reducing the negative effects of density on seedling recruitment, and removing insects increases seedling survival and alters plant community composition; this demonstrates the crucial role of pathogens and insects in maintaining and structuring tropical forest plant diversity.

In Arabidopsis, the RNA-directed DNA methylation pathway is important for establishing and maintaining DNA methylation — here Pol V is shown to depend on SUVH2 and SUVH9, where both of these proteins are proposed to bind specifically to methylated DNA to recruit Pol V, providing a self-reinforcing loop mechanism for maintenance of RNA-directed DNA methylation.

In the search for stable and accurate atomic clocks, many-atom lattice clocks have shown higher precision than clocks based on single trapped ions, but have been less accurate; here, a stable many-atom clock is demonstrated that has accuracy better than single-ion clocks.

Warming of the north and tropical Atlantic Ocean, which is associated in part with the Atlantic Multidecadal Oscillation (a leading mode of sea surface temperature variability), is shown to affect sea-level pressure in the Amundsen Sea, explaining the accelerated warming of and sea-ice redistribution around the Antarctic Peninsula.