Trigoniulus corallinus Genome sequencing and assembly

The Myriapoda including millipedes and centipedes is of major importance in terrestrial ecology and nutrients recycling. Here, we sequenced and assembled two chromosomal-scale genomes of millipedes Helicorthomorpha holstii (182 Mb, N50 18.11 Mb mainly on 8 pseudomolecules) and Trigoniulus corallinus (449 Mb, N50 26.78 Mb mainly on 15 pseudomolecules). Unique defense system, genomic features, and gene regulation in millipedes that are not observed in other arthropods are unmasked. Millipede possesses unique ozadene defensive gland unlike the venomous forcipules in centipedes, and sets of antimicrobial genes involved are revealed with proteomics. Macro-synteny analyses revealed highly conserved genomic blocks between centipede and the two millipedes. Tight Hox and the first loose ecdysozoan ParaHox homeobox clusters are identified, but millipede-specific genomic rearrangement including Hox3 is observed. The Argonaute proteins for loading small RNAs are duplicated in both millipedes but, unlike the situation of insects, an argonaute duplicate becomes a pseudogene. Evidence of post-transcriptional modification in small RNAs including species-specific microRNA arm switching that provide differential gene regulation is also obtained. Millipede genomes uncover the unique adaptation of genes and microRNAs regulation during arthropod evolution, and provides a foundation for further understanding the terrestrial ecosystem and evolution.