Volume 551 Number 7681



News Features

News & Views

Machinery that guides immunity p.442

The peptide-loading complex is key to the initiation of an immune response that raises killer T cells in vertebrates. Its structure has now been determined, and might provide information that improves immune protection.

doi: 10.1038/d41586-017-07268-8

Thunderous nuclear reactions p.443

The discovery that thunderstorms can trigger nuclear reactions provides insight into the physics of atmospheric electricity and unveils a previously unknown natural source of radioactive isotopes on Earth.

doi: 10.1038/d41586-017-07266-w

How T cells spot tumour cells p.444

Immunotherapy can reawaken T cells to destroy tumour cells. Modelling of tumour and T-cell interactions suggests why certain tumour cells are targeted and improves predictions of immunotherapy outcome.

doi: 10.1038/d41586-017-07267-9

Crowdsourcing Earth's microbes p.446

A large-scale study has been assessing microbial diversity by analysing DNA sequences from samples submitted by scientists around the globe. The initial results are now being used to create an open-access resource. See Article p.457

doi: 10.1038/nature24756

Super-reactive catalyst for bond cleavage p.447

Carbon–hydrogen bonds in organic molecules can be cut to install other chemical groups on the carbon atom, but these reactions have been limited. A catalytic palladium complex opens up fresh opportunities.

doi: 10.1038/d41586-017-07270-0

Layered-up regulation in the developing brain p.448

Modification of messenger RNAs through a process called m6A methylation facilitates dynamic temporal regulation of RNA levels in neural precursor cells, enabling fine-tuning of developing neuronal circuits in the brain.

doi: 10.1038/d41586-017-07269-7



Genome sequence of the progenitor of the wheat D genome Aegilops tauschii OPEN p.498

Aegilops tauschii is the diploid progenitor of the D genome of hexaploid wheat1 (Triticum aestivum, genomes AABBDD) and an important genetic resource for wheat2–4. The large size and highly repetitive nature of the Ae. tauschii genome has until now precluded the development of a reference-quality genome sequence5. Here we use an array of advanced technologies, including orderedclone genome sequencing, whole-genome shotgun sequencing, and BioNano optical genome mapping, to generate a reference-quality genome sequence for Ae. tauschii ssp. strangulata accession AL8/78, which is closely related to the wheat D genome. We show that compared to other sequenced plant genomes, including a much larger conifer genome, the Ae. tauschii genome contains unprecedented amounts of very similar repeated sequences. Our genome comparisons reveal that the Ae. tauschii genome has a greater number of dispersed duplicated genes than other sequenced genomes and its chromosomes have been structurally evolving an order of magnitude faster than those of other grass genomes. The decay of colinearity with other grass genomes correlates with recombination rates along chromosomes. We propose that the vast amounts of very similar repeated sequences cause frequent errors in recombination and lead to gene duplications and structural chromosome changes that drive fast genome evolution.

doi: 10.1038/nature24486