72 research outputs found
A heterozygous moth genome provides insights into herbivory and detoxification
How an insect evolves to become a successful herbivore is of profound biological and practical importance. Herbivores are often adapted to feed on a specific group of evolutionarily and biochemically related host plants1, but the genetic and molecular bases for adaptation to plant defense compounds remain poorly understood2. We report the first whole-genome sequence of a basal lepidopteran species, Plutella xylostella, which contains 18,071 protein-coding and 1,412 unique genes with an expansion of gene families associated with perception and the detoxification of plant defense compounds. A recent expansion of retrotransposons near detoxification-related genes and a wider system used in the metabolism of plant defense compounds are shown to also be involved in the development of insecticide resistance. This work shows the genetic and molecular bases for the evolutionary success of this worldwide herbivore and offers wider insights into insect adaptation to plant feeding, as well as opening avenues for more sustainable pest management.Minsheng You … Simon W Baxter … et al
Does or did the supernova remnant Cassiopeia A operate as a PeVatron?
For decades, supernova remnants (SNRs) have been considered the prime sources
of Galactic Cosmic rays (CRs). But whether SNRs can accelerate CR protons to
PeV energies and thus dominate CR flux up to the knee is currently under
intensive theoretical and phenomenological debate. The direct test of the
ability of SNRs to operate as CR PeVatrons can be provided by ultrahigh-energy
(UHE; ~TeV) -rays. In this context, the historical
SNR Cassiopeia A (Cas A) is considered one of the most promising target for UHE
observations. This paper presents the observation of Cas A and its vicinity by
the LHAASO KM2A detector. The exceptional sensitivity of LHAASO KM2A in the UHE
band, combined with the young age of Cas A, enabled us to derive stringent
model-independent limits on the energy budget of UHE protons and nuclei
accelerated by Cas A at any epoch after the explosion. The results challenge
the prevailing paradigm that Cas A-type SNRs are major suppliers of PeV CRs in
the Milky Way.Comment: 11 pages, 3 figures, Accepted by the APJ
Measurement of ultra-high-energy diffuse gamma-ray emission of the Galactic plane from 10 TeV to 1 PeV with LHAASO-KM2A
The diffuse Galactic -ray emission, mainly produced via interactions
between cosmic rays and the interstellar medium and/or radiation field, is a
very important probe of the distribution, propagation, and interaction of
cosmic rays in the Milky Way. In this work we report the measurements of
diffuse -rays from the Galactic plane between 10 TeV and 1 PeV
energies, with the square kilometer array of the Large High Altitude Air Shower
Observatory (LHAASO). Diffuse emissions from the inner
(, ) and outer
(, ) Galactic plane are detected with
and significance, respectively. The outer Galactic
plane diffuse emission is detected for the first time in the very- to
ultra-high-energy domain (~TeV). The energy spectrum in the inner Galaxy
regions can be described by a power-law function with an index of
, which is different from the curved spectrum as expected from
hadronic interactions between locally measured cosmic rays and the
line-of-sight integrated gas content. Furthermore, the measured flux is higher
by a factor of than the prediction. A similar spectrum with an index of
is found in the outer Galaxy region, and the absolute flux for
TeV is again higher than the prediction for hadronic
cosmic ray interactions. The latitude distributions of the diffuse emission are
consistent with the gas distribution, while the longitude distributions show
clear deviation from the gas distribution. The LHAASO measurements imply that
either additional emission sources exist or cosmic ray intensities have spatial
variations.Comment: 12 pages, 8 figures, 5 tables; accepted for publication in Physical
Review Letters; source mask file provided as ancillary fil
Dictionary‐induced least squares framework for multi‐view dimensionality reduction with multi‐manifold embeddings
This study proposes a novel dimensionality reduction (DR) method for multi‐view datasets. The principal component analysis (PCA) idea of minimising least squares reconstruction errors is extended to consider both data distribution and penalty weights called dictionary to recover outliers free global structures from missing and noisy data points. In this way, PCA is viewed as a special instance of the authors’ proposed dictionary induced least squares framework (DLS). Furthermore, to appropriately handle multi‐view DR, we combine the DLS with multiple manifold embeddings (DLSME). Therefore it can obtain lower projections while maintaining a balance between preserving global structures with DLS and local structures with multi‐manifold embeddings. Extensive experiments on object and face recognition datasets verify that the DLS achieves better classification results with lower dimensional projections than PCA. Also, on many multi‐view datasets of visual recognition and web image annotation, the DLSME method demonstrates more effectiveness than Graph‐Laplacian PCA (gLPCA), robust PCA‐optimal mean, canonical correlation analysis (CCA), bilinear models (BLM), neighbourhood preserving embedding, locality preserving projections, and locality sensitive discriminant analysis
Aegilops tauschii draft genome sequence reveals a gene repertoire for wheat adaptation
About 8,000 years ago in the Fertile Crescent, a spontaneous hybridization of the wild diploid grass Aegilops tauschii (2n = 14; DD) with the cultivated tetraploid wheat Triticum turgidum (2n = 4x = 28; AABB) resulted in hexaploid wheat (T. aestivum; 2n = 6x = 42; AABBDD). Wheat has since become a primary staple crop worldwide as a result of its enhanced adaptability to a wide range of climates and improved grain quality for the production of baker's flour. Here we describe sequencing the Ae. tauschii genome and obtaining a roughly 90-fold depth of short reads from libraries with various insert sizes, to gain a better understanding of this genetically complex plant. The assembled scaffolds represented 83.4% of the genome, of which 65.9% comprised transposable elements. We generated comprehensive RNA-Seq data and used it to identify 43,150 protein-coding genes, of which 30,697 (71.1%) were uniquely anchored to chromosomes with an integrated high-density genetic map. Whole-genome analysis revealed gene family expansion in Ae. tauschii of agronomically relevant gene families that were associated with disease resistance, abiotic stress tolerance and grain quality. This draft genome sequence provides insight into the environmental adaptation of bread wheat and can aid in defining the large and complicated genomes of wheat species
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