The phylogeny of leaf beetles (Chrysomelidae) inferred from mitochondrial genomes

The high-level classification of Chrysomelidae (leaf beetles) currently recognizes 12 or 13 well-established subfamilies, but the phylogenetic relationships among them remain ambiguous. Full mitochondrial genomes were newly generated for 27 taxa and combined with existing GenBank data to provide a dataset of 108 mitochondrial genomes covering all subfamilies. Phylogenetic analysis under maximum likelihood and Bayesian inference recovered the monophyly of all subfamilies, except that Timarcha was split from Chrysomelinae in some analyses. Three previously recognized major clades of Chrysomelidae were broadly supported: the ‘chrysomeline’ clade consisting of (Chrysomelinae (Galerucinae + Alticinae)); the ‘sagrine’ clade with internal relationships of ((Bruchinae + Sagrinae) + (Criocerinae + Donaciinae)), and the ‘eumolpine’ clade comprising (Spilopyrinae (Cassidinae (Eumolpinae (Cryptocephalinae + Lamprosomatinae)))). Relationships among these clades differed between data treatments and phylogenetic algorithms, and were complicated by two additional deep lineages, Timarcha and Synetinae. Various topological tests favoured the PhyloBayes software as the preferred inference method, resulting in the arrangement of (chrysomelines (eumolpines + sagrines)), with Timarcha placed as sister to the chrysomeline clade and Synetinae as a deep lineage splitting near the base. Whereas mitogenomes provide a solid framework for the phylogeny of Chrysomelidae, the basal relationships do not agree with the topology of existing molecular studies and remain one of the most difficult problems of Chrysomelidae phylogenetics.This research was supported by grants from the National Science Foundation of China (nos 31772496, 31301900 and 3181101902), and the President's International Fellowship Initiative of the Chinese Academy to APV. APV's research on Coleoptera phylogenetics was funded by the Leverhulme Trust (F/00696/P and IAF‐2018‐038) and mitogenome sequencing was supported by the Natural History Museum Biodiversity Initiative.Peer Reviewe

Cell-autonomous complementation of mlo resistance using a biolistic transient expression system

The barley geneMloencodes a prototype of a novel class of plant proteins. Inmlomutants, absence of the 60 kDa wild-type Mlo protein results in broad-spectrum resistance to the powdery mildew fungus,Erysiphe graminisf. sp.hordei. To directly assess its function,Mlowas transiently expressed with a marker gene encoding a modified green fluorescent protein (GFP) in leaf epidermal cells ofmloresistant barley lines. Fungal inoculation of epidermal cells transfected with wild-typeMloled to haustorium formation and abundant sporulation. Therefore, expression of the wild-typeMlogene, inmloresistant genotypes, is both necessary and sufficient to restore susceptibility to fungal attack. Complementation ofmloresistance alleles was restricted to single host cells, indicating a cell-autonomous function for the wild-type Mlo protein. We discuss our findings with respect to source–sink relationships of plants and biotrophic fungi and the potentially wide-ranging use of the transient complementation assay to analyse host compatibility and defence in response to powdery mildew attack

Mechanical behavior of a bulk nanostructured iron alloy

Bulk, fully dense materials were prepared from Fe-10Cu with grain diameters between 45 run and 1.7 yum. The materials were prepared by ball milling of powders in a glove box, followed by hot isostatic pressing (hipping) or powder forging. Larger grain sizes were obtained by thermal treatment of the consolidated powders. The bulk materials were relatively clean, with oxygen levels below 1500 wpm and other contaminants less than 0.1 at. pet. The mechanical behavior of these materials was unique. At temperatures from 77 to 470 K, the first and only mechanism of plastic deformation was intense shear banding, which was accompanied by a perfectly plastic stress-strain response (absence of strain hardening). There was a large tension-compression asymmetry in the strength, and the shear bands did not occur on the plane of maximum shear stress or the plane of zero extension. This behavior, while unusual for metals, has been observed in amorphous polymers and metallic glasses. On the other hand, the fine-grained Fe-10Cu materials behaved like coarse-grained iron in some respects, particularly by obeying the Hall-Petch equation with constants reasonably close to those of pure iron and by exhibiting low-temperature mechanical behavior which was very similar to that of steels. Transmission electron microscopy (TEM) studies found highly elongated grains within shear bands, indicating that shear banding occurred by a dislocation-based mechanism, at least at grain sizes above 100 nm. Similarities and differences between the fine-grained Fe-10Cu and metals, polymers, metallic glasses, radiation-damaged metals, and quench-damaged metals are discussed