Volume 550 Number 7674

Editorials

News

News Features

News & Views

Zapping viral RNAs p.46

The discovery that the host defence protein ZAP specifically targets viral RNAs that are rich in a particular pair of adjacent bases — cytosine followed by guanine — sheds light on the evolution of viral RNA genomes.

doi: 10.1038/nature24140

Material change for X-ray detectors p.47

The X-ray sensitivity of radiology instruments is limited by the materials used in their detectors. A material from the perovskite family of semiconductors could allow lower doses of X-rays to be used for medical imaging. See Letter p.87

doi: 10.1038/550047a

A global plan for nature conservation p.48

An international movement is calling for at least half of the Earth to be allocated for conservation. A global study now reveals that, in many ecoregions, enough habitat exists to reach this goal, and ideas are proposed for the next steps needed.

doi: 10.1038/nature24144

Computational design hits record resolution p.50

A supercomputer-powered design technique enables the discovery of efficient mechanical structures that have an unprecedented level of detail. The findings provide insights into both physical and biological structures. See Letter p.84

doi: 10.1038/550050a

A matter of time for tropical diversity p.51

There is a species-diversity gradient on Earth, with the greatest diversity found near the Equator. Analysis of forest data now reveals a mechanism aiding species coexistence in the tropics that might underlie this phenomenon.

doi: 10.1038/nature24142

Review

Articles

Letters

Retrograde semaphorin–plexin signalling drives homeostatic synaptic plasticity p.109

Homeostatic signalling systems ensure stable but flexible neural activity and animal behaviour. Presynaptic homeostatic plasticity is a conserved form of neuronal homeostatic signalling that is observed in organisms ranging from Drosophila to human. Defining the underlying molecular mechanisms of neuronal homeostatic signalling will be essential in order to establish clear connections to the causes and progression of neurological disease. During neural development, semaphorin–plexin signalling instructs axon guidance and neuronal morphogenesis. However, semaphorins and plexins are also expressed in the adult brain. Here we show that semaphorin 2b (Sema2b) is a target-derived signal that acts upon presynaptic plexin B (PlexB) receptors to mediate the retrograde, homeostatic control of presynaptic neurotransmitter release at the neuromuscular junction in Drosophila. Further, we show that Sema2b–PlexB signalling regulates presynaptic homeostatic plasticity through the cytoplasmic protein Mical and the oxoreductase-dependent control of presynaptic actin. We propose that semaphorin–plexin signalling is an essential platform for the stabilization of synaptic transmission throughout the developing and mature nervous system. These findings may be relevant to the aetiology and treatment of diverse neurological and psychiatric diseases that are characterized by altered or inappropriate neural function and behaviour.

doi: 10.1038/nature24017