Abstract:
The tomato russet mite, Aculops lycopersici, is among the smallest animals on earth. It
is a worldwide pest on tomato and can potently suppress the host’s natural resistance. We
sequenced its genome, the first of an eriophyoid, and explored whether there are genomic
features associated with the mite’s minute size and lifestyle. At only 32.5 Mb, the genome is the
smallest yet reported for any arthropod and, reminiscent of microbial eukaryotes, exceptionally
streamlined. It has few transposable elements, tiny intergenic regions, and is remarkably intronpoor, as more than 80% of coding genes are intronless. Furthermore, in accordance with ecological
specialization theory, this defense-suppressing herbivore has extremely reduced environmental
response gene families such as those involved in chemoreception and detoxification. Other losses
associate with this species’ highly derived body plan. Our findings accelerate the understanding of
evolutionary forces underpinning metazoan life at the limits of small physical and genome size.
