Bdelloid rotifers: a case-study in non-model genome diversity and evolution Flashcards
sexual reproduction of bdelloid rotifers
no males, fully asexual lineage (two-fold cost of males etc etc)
asexuality and polyploidy
polyploidy may help mitigate some of the issues with asexuality- e.g. helping mask deleterious mutations
rotifers and polyploidy
seemed to have been tetraploid at some point, but has since degenerated
example of an expanded gene family in rotifers
TE silencing/suppression (20-50 copies, where most animals have 10ish copies)- reinforces idea that TEs are more damaging in asexual organisms
why might chromosomes still be in pairs even in an asexual lineage?
see recombination without sex- good for maintaining heterozygosity
possibly also good for stress tolerance- losing a copy of something is less deep and allows HR
asexuality and stress
asexual organisms actually seem to live in the more stressful environments- but this discounts biotic stresses so also maybe not
term including both HGT and meiotic sex
genetic exchange
example of asexuality encouraging disease
bananas- asexual more prone to diseases e.g. Panama disease
rotifer disease study
looked at which genes are upregulated vs downregulated in more disease-prone vs more resistant species
found that there is excess HGT in the genes which are up- or downregulated during disease (downreg- negative repressors of upreg stuff, mostly)
gene transfer, biotic conflict, and sex
HGTs used for biotic stresses are much higher than for abiotic, seems like this is where rotifers have ‘looked externally’
limitations of using HGT to make hypotheses about genetic exchange more generally
slow
not between rotifers
doesn’t shuffle alleles
only 10% of the genome involved
> therefore not really like sex
‘reverse ecology’ approaches
inferring how genes affect phenotype- can be studied by looking at comparative genomics, mutagenesis, inserting genes into other organisms if possible
