royalsociety | Selfish genes demonstrate transmission bias and invade sexual
populations despite conferring no benefit to their hosts. While
the molecular genetics and evolutionary dynamics of
selfish genes are reasonably well characterized, their effects on hosts
are not. Homing endonuclease genes (HEGs) are one
well-studied family of selfish genes that are assumed to be benign.
However,
we show that carrying HEGs is costly for Saccharomyces cerevisiae,
demonstrating that these genetic elements are not necessarily benign
but maybe parasitic. We estimate a selective load of
approximately 1–2% in ‘natural’ niches. The second
aspect we examine is the ability of HEGs to affect hosts' sexual
behaviour.
As all selfish genes critically rely on sex for
spread, then any selfish gene correlated with increased host sexuality
will
enjoy a transmission advantage. While classic
parasites are known to manipulate host behaviour, we are not aware of
any evidence
showing a selfish gene is capable of affecting host
promiscuity. The data presented here show a selfish element may
increase
the propensity of its eukaryote host to undergo sex
and along with increased rates of non-Mendelian inheritance, this may
counterbalance mitotic selective load and promote
spread. Demonstration that selfish genes are correlated with increased
promiscuity
in eukaryotes connects with ideas suggesting that
selfish genes promoted the evolution of sex initially.
