The draft genome of the invasive walking stick, Medauroidea extradendata, reveals extensive lineage-specific gene family expansions of cell wall degrading enzymes in Phasmatodea

Abstract

Plant cell wall components are the most abundant macromolecules on Earth. The study of the breakdown of these molecules is thus a central question in biology. Surprisingly, plant cell wall breakdown by herbivores is relatively poorly understood, as nearly all early work focused on the mechanisms used by symbiotic microbes to breakdown plant cell walls in insects such as termites. Recently, however, it has been shown that many organisms make endogenous cellulases. Insects, and other arthropods, in particular have been shown to express a variety of plant cell wall degrading enzymes in many gene families with the ability to break down all the major components of the plant cell wall. Here we report the genome of a walking stick, Medauroidea extradentata, an obligate herbivore that makes uses of endogenously produced plant cell wall degrading enzymes. We present a draft of the 3.3Gbp genome along with an official gene set that contains a diversity of plant cell wall degrading enzymes. We show that at least one of the major families of plant cell wall degrading enzymes, the pectinases, have undergone a striking lineage-specific gene family expansion in the Phasmatodea. This genome will be a useful resource for comparative evolutionary studies with herbivores in many other clades and will help elucidate the mechanisms by which metazoans breakdown plant cell wall components.\n\nData availabilityThe Medauroidea extradentata genome assembly, Med v1.0, is available for download via NCBI (Bioproject: PRJNA369247). The genome, annotation files, and official gene set Mext_OGS_v1.0 are also available at the i5k NAL workspace (https://i5k.nal.usda.gov/medauroidea-extradentata) and at github (https://github.com/pbrec/medauroidea_genome_resources). The genomic raw reads are available via NCBI SRA: SRR6383867 and the raw transcriptomic reads are available at NCBI SRA: SRR6383868, SRR6383869.