Horizontal gene transfer and evolutionary consequence of gene loss in myriapods

Animals have fascinating diversity of life forms. Analyses of the available genome sequence reveals dynamic evolution of gene gain and loss at different lineages in the animal tree of life (e.g. Albalat and Canestro 2016; Sharma et al 2018; Fernandez and Gabaldon 2020; Guijarro-Clarke et al 2020; Jebb et al 2020). Gene gain via another kingdom as well as the evolutionary consequence of gene loss are generally ignored and difficult to interpret. Here we sequenced six new myriapod genomes at key phylogenetic positions of this understudied arthropod lineage (three millipedes and three centipedes). Comparison of myriapod genomes revealed multiple horizontal gene transfer (HGT) of genes shared between centipedes, including <i>glucose/arabinose dehydrogenase</i> that happened at the last common of ancestor of centipedes, while there was no detectable HGT shared between the millipedes. In all millipede lineages, the loss of <i>juvenile hormone O-methyltransferase</i>, a key enzyme in catalysing the last step of sesquiterpenoid hormone methyl farnesoate production in arthropods was revealed. These findings provided the first evidence of shared HGT in the last common ancestor of centipede ancestor, while gene loss event could indeed happen in endocrine system in contrary to the conventional view of stepwise gene gain resulting in diversity of animal physiology for adaptation to environment.