(
2010-01)
Gladyshev, Eugene A.; Arkhipova, Irina R.
Bdelloid rotifers are microscopic invertebrate animals best known for their ancient
asexuality and the ability to survive desiccation at any life stage. Both factors are expected to
have a profound influence on their genome structure. Recent molecular studies demonstrated
that, while the gene-rich regions of bdelloid genomes are organized as co-linear pairs of closely
related sequences and depleted in repetitive DNA, subtelomeric regions harbor diverse
transposable elements and horizontally acquired genes of foreign origin. While asexuality is
expected to result in depletion of deleterious transposons, only desiccation appears to have the
power to produce all of the uncovered genomic peculiarities. Repair of desiccation-induced DNA
damage would require the presence of a homologous template, maintaining co-linear pairs in
gene-rich regions, and selecting against insertion of repetitive DNA which might cause
chromosomal rearrangements. Desiccation may also induce a transient state of competence in
recovering animals, allowing them to acquire environmental DNA. Even if bdelloids engage in
rare or obscure forms of sexual reproduction, all these features could still be present. The relative
contribution of asexuality and desiccation to genome organization may be clarified by analyzing
whole-genome sequences and comparing foreign gene and transposon content in species which
lost the ability to survive desiccation.
