The Easter Egg Weevil (Pachyrhynchus) genome reveals syntenic patterns in Coleoptera across 200 million years of evolution

Patterns of genomic architecture across insects remain largely undocumented or decoupled from a broader phylogenetic context. For instance, it is unknown whether translocation rates differ between insect orders. We address broad scale patterns of genome architecture across Insecta by examining synteny in a phylogenetic framework from open-source insect genomes. To accomplish this, we add a chromosome level genome to a crucial lineage, Coleoptera. Our assembly of the Pachyrhynchus sulphureomaculatus genome is the first chromosome scale genome for the hyperdiverse Phytophaga lineage and currently the largest insect genome assembled to this scale. The genome is significantly larger than those of other weevils, and this increase in size is caused by repetitive elements. Our results also indicate that, among beetles, there are instances of long-lasting (>200 Ma) localization of genes to a particular chromosome with few translocation events. While some chromosomes have a paucity of translocations, intra-chromosomal synteny was almost absent, with gene order thoroughly shuffled along a chromosome. This large amount of reshuffling within chromosomes with few inter-chromosomal events contrasts with patterns seen in mammals in which the chromosomes tend to exchange larger blocks of material more readily. To place our findings in an evolutionary context, we compared syntenic patterns across Insecta in a phylogenetic framework. For the first time, we find that synteny decays at an exponential rate relative to phylogenetic distance. Additionally, there are significant differences in decay rates between insect orders, this pattern was not driven by Lepidoptera alone which has a substantially different rate.

The genome sequence of Sorbus pohuashanensis provides insights into population evolution and leaf sunburn response

Sorbus pohuashanensis is a potential horticulture and medicinal plant, but its genomic and genetic background remains unknown. Here, we de novo sequenced and assembled the S. pohuashanensis (Hance) Hedl. reference genome using PacBio long reads. Based on the new reference genome, we resequenced a core collection of 22 Sorbus spp. samples, which were divided into two groups (G1 and G2) based on phylogenetic and PCA analysis. These phylogenetic clusters were highly in accordance with the classification based on leaf shape. Natural hybridization between the G1 and G2 groups was evidenced by a sample (R21) with a highly heterozygous genotype. Nucleotide diversity (π) analysis showed that G1 has a higher diversity than G2, and that G2 originated from G1. During the evolution process, the gene families involved in photosynthesis pathways expanded and gene families involved in energy consumption contracted. Comparative genome analysis showed that S. pohuashanensis has a high level of chromosomal synteny with Malus domestica and Pyrus communis. RNA-seq data suggested that flavonol biosynthesis and heat-shock protein (HSP)-heat-shock factor (HSF) pathways play important roles in protection against sunburn. This research provides new insight into the evolution of Sorbus spp. genomes. In addition, the genomic resources and the identified genetic variations, especially those genes related to stress resistance, will help future efforts to introduce and breed Sorbus spp.

The Easter Egg Weevil (Pachyrhynchus) genome reveals synteny in Coleoptera across 200 million years of evolution

Patterns of genomic architecture across insects remain largely undocumented or decoupled from a broader phylogenetic context. For instance, it is unknown whether translocation rates differ between insect orders? We address broad scale patterns of genome architecture across Insecta by examining synteny in a phylogenetic framework from open source insect genomes. To accomplish this, we add a chromosome level genome to a crucial lineage, Coleoptera. Our assembly of the Pachyrhynchus sulphureomaculatus genome is the first chromosome scale genome for the hyperdiverse Phytophaga lineage and currently the largest insect genome assembled to this scale. The genome is significantly larger than those of other weevils, and this increase in size is caused by repetitive elements. Our results also indicate that, among beetles, there are instances of long-lasting (>200 Ma) localization of genes to a particular chromosome with few translocation events. While some chromosomes have a paucity of translocations, intra-chromosomal synteny was almost absent, with gene order thoroughly shuffled along a chromosome. To place our findings in an evolutionary context, we compared syntenic patterns across Insecta. We find that synteny largely scales with clade age, with younger clades, such as Lepidoptera, having especially high synteny. However, we do find subtle differences in the maintenance of synteny and its rate of decay among the insect orders.

Independent Co-option of a Tailed Bacteriophage into a Killing Complex in Pseudomonas

Competition between microbes is widespread in nature, especially among those that are closely related. To combat competitors, bacteria have evolved numerous protein-based systems (bacteriocins) that kill strains closely related to the producer. In characterizing the bacteriocin complement and killing spectra for the model strain P. syringae B728a, we discovered its activity was not linked to any predicted bacteriocin, but is derived from a prophage. Instead of encoding an active prophage, this region encodes a bacteriophage-derived bacteriocin, termed an R-type syringacin. The R-type syringacin is striking in its convergence with the well-studied R-type pyocin of P. aeruginosa in both chromosomal synteny and molecular function. Genomic alignment, amino acid percent sequence identity, and phylogenetic inference all support a scenario where the R-type syringacin has been co-opted independently of the R-type pyocin. Moreover, the presence of this region is conserved among several other Pseudomonas species, and thus is likely important for intermicrobial interactions throughout this important genus.

Deciphering deuterostome phylogeny: molecular, morphological and palaeontological perspectives

Deuterostomes are a monophyletic group of animals that include the vertebrates, invertebrate chordates, ambulacrarians and xenoturbellids. Fossil representatives from most major deuterostome groups, including some phylum-level crown groups, are found in the Lower Cambrian, suggesting that evolutionary divergence occurred in the Late Precambrian, in agreement with some molecular clock estimates. Molecular phylogenies, larval morphology and the adult heart/kidney complex all support echinoderms and hemichordates as a sister grouping (Ambulacraria). Xenoturbellids are a relatively newly discovered phylum of worm-like deuterostomes that lacks a fossil record, but molecular evidence suggests that these animals are a sister group to the Ambulacraria. Within the chordates, cephalochordates share large stretches of chromosomal synteny with the vertebrates, have a complete Hox complex and are sister group to the vertebrates based on ribosomal and mitochondrial gene evidence. In contrast, tunicates have a highly derived adult body plan and are sister group to the vertebrates based on the analyses of concatenated genomic sequences. Cephalochordates and hemichordates share gill slits and an acellular cartilage, suggesting that the ancestral deuterostome also shared these features. Gene network data suggest that the deuterostome ancestor had an anterior–posterior body axis specified by Hox and Wnt genes, a dorsoventral axis specified by a BMP/chordin gradient, and was bilaterally symmetrical with left–right asymmetry determined by expression of nodal .