The red palm weevil (RPW), Rhynchophorus ferrugineus (Coleoptera: Curculionidae), is the most devastating pest of palm trees worldwide. Mitigation of the economic and biodiversity impact it causes is an international priority that could be greatly aided by a better understanding of its biology and genetics. Despite its relevance, the biology of the RPW remains poorly understood, and research on management strategies often focuses on outdated empirical methods that produce sub-optimal results. With the development of omics approaches in genetic research, new avenues for pest control are becoming increasingly feasible. For example, genetic engineering approaches become available once a species’s target genes are well characterized in terms of their sequence, but also population variability, epistatic interactions, and more. In the last few years alone, there have been major advances in omics studies of the RPW. Multiple draft genomes are currently available, along with short and long-read transcriptomes, and metagenomes, which have facilitated the identification of genes of interest to the RPW scientific community. This review describes omics approaches previously applied to RPW research, highlights findings that could be impactful for pest management, and emphasizes future opportunities and challenges in this area of research.

The red palm weevil Rhynchophorus ferrugineus (Coleoptera: Curculionidae) is an economically-important invasive species that attacks multiple species of palm trees around the world. A better understanding of gene content and function in R. ferrugineus has the potential to inform pest control strategies and thereby mitigate economic and biodiversity losses caused by this species. Using 10x Genomics linked-read sequencing, we produced a haplotype-resolved diploid genome assembly for R. ferrugineus from a single heterozygous individual with modest sequencing coverage ( $$\sim$$∼ 62x). Benchmarking against conserved single-copy Arthropod orthologs suggests both pseudo-haplotypes in our R. ferrugineus genome assembly are highly complete with respect to gene content, and do not suffer from haplotype-induced duplication artifacts present in a recently published hybrid assembly for this species. Annotation of the larger pseudo-haplotype in our assembly provides evidence for 23,413 protein-coding loci in R. ferrugineus, including over 13,000 predicted proteins annotated with Gene Ontology terms and over 6000 loci independently supported by high-quality Iso-Seq transcriptomic data. Our assembly also includes 95% of R. ferrugineus chemosensory, detoxification and neuropeptide-related transcripts identified previously using RNA-seq transcriptomic data, and provides a platform for the molecular analysis of these and other functionally-relevant genes that can help guide management of this widespread insect pest.

Animal cell lines often undergo extreme genome restructuring events, including polyploidy and segmental aneuploidy that can impede de novo whole-genome assembly (WGA). In some species like Drosophila, cell lines also exhibit massive proliferation of transposable elements (TEs). To better understand the role of transposition during animal cell culture, we sequenced the genome of the tetraploid Drosophila S2R+ cell line using long-read and linked-read technologies. WGAs for S2R+ were highly fragmented and generated variable estimates of TE content across sequencing and assembly technologies. We therefore developed a novel WGA-independent bioinformatics method called TELR that identifies, locally assembles, and estimates allele frequency of TEs from long-read sequence data (https://github.com/bergmanlab/telr). Application of TELR to a ∼130x PacBio dataset for S2R+ revealed many haplotype-specific TE insertions that arose by transposition after initial cell line establishment and subsequent tetraploidization. Local assemblies from TELR also allowed phylogenetic analysis of paralogous TEs, which revealed that proliferation of TE families in vitro can be driven by single or multiple source lineages. Our work provides a model for the analysis of TEs in complex heterozygous or polyploid genomes that are recalcitrant to WGA and yields new insights into the mechanisms of genome evolution in animal cell culture.

Cell culture systems allow key insights into biological mechanisms yet suffer from irreproducible outcomes in part because of cross-contamination or mislabeling of cell lines. Cell line misidentification can be mitigated by the use of genotyping protocols, which have been developed for human cell lines but are lacking for many important model species. Here, we leverage the classical observation that transposable elements (TEs) proliferate in cultured Drosophila cells to demonstrate that genome-wide TE insertion profiles can reveal the identity and provenance of Drosophila cell lines. We identify multiple cases where TE profiles clarify the origin of Drosophila cell lines (Sg4, mbn2, and OSS_E) relative to published reports, and also provide evidence that insertions from only a subset of long-terminal repeat retrotransposon families are necessary to mark Drosophila cell line identity. We also develop a new bioinformatics approach to detect TE insertions and estimate intra-sample allele frequencies in legacy whole-genome sequencing data (called ngs_te_mapper2), which revealed loss of heterozygosity as a mechanism shaping the unique TE profiles that identify Drosophila cell lines. Our work contributes to the general understanding of the forces impacting metazoan genomes as they evolve in cell culture and paves the way for high-throughput protocols that use TE insertions to authenticate cell lines in Drosophila and other organisms.

Satellite DNAs are among the most abundant repetitive DNAs found in eukaryote genomes, where they participate in a variety of biological roles, from being components of important chromosome structures to gene regulation. Experimental methodologies used before the genomic era were insufficient, too laborious and time-consuming to recover the collection of all satDNAs from a genome. Today, the availability of whole sequenced genomes combined with the development of specific bioinformatic tools are expected to foster the identification of virtually all the “satellitome” of a particular species. While whole genome assemblies are important to obtain a global view of genome organization, most of them are incomplete and lack repetitive regions. We applied short-read sequencing and similarity clustering in order to perform a de novo identification of the most abundant satellite families in two Drosophila species from the virilis group: Drosophila virilis and D. americana, using the Tandem Repeat Analyzer (TAREAN) and RepeatExplorer pipelines. These species were chosen because they have been used as models to understand satDNA biology since the early 70’s. We combined the computational approach with data from the literature and chromosome mapping to obtain an overview of the major tandem repeat sequences of these species. The fact that all of the abundant tandem repeats (TRs) we detected were previously identified in the literature allowed us to evaluate the efficiency of TAREAN in correctly identifying true satDNAs. Our results indicate that raw sequencing reads can be efficiently used to detect satDNAs, but that abundant tandem repeats present in dispersed arrays or associated with transposable elements are frequent false positives. We demonstrate that TAREAN with its parent method RepeatExplorer may be used as resources to detect tandem repeats associated with transposable elements and also to reveal families of dispersed tandem repeats.

Although normally a harmless commensal, Candida albicans, it is also one of the most common causes of bloodstream infections in the U.S.. Candida albicans has long been considered an obligate commensal, however, recent studies suggest it can live outside animal hosts. Here, we have generated PacBio sequences and phased genome assemblies for three C. albicans strains from oak trees (NCYC 4144, NCYC 4145, and NCYC 4146). PacBio datasets are high depth (over 400 fold coverage) and more than half of the sequencing data is contained in reads longer than 15 kb. Primary assemblies showed high contiguity with several chromosomes for each strain recovered as single contigs, and greater than half of the alternative haplotype sequence was assembled in haplotigs at least 174 kb long. Using these assemblies we were able to identify structural polymorphisms, including a polymorphic inversion over 100 kb in length. These results show that phased de novo diploid assemblies for C. albicans can enable the study of genomic variation within and among strains of an important fungal pathogen.