RNA editing confers a 'heterozygote advantage' to fungi

What is it about?

RNA editing is hypothesized to facilitate adaptive evolution via flexibly diversifying the proteome temporally or spatially. However, direct experimental evidence is lacking. This study unveils the functional importance of conserved missense adenosine-to-inosine (A-to-I) RNA editing (CME) sites in Fusarium graminearum and provides convincing experimental evidence for the adaptive advantages of two CME sites. The first CME site drives the CME5 gene gaining a new important function in ascus and ascospore formation during evolution. Having an editable A at this site is fitter than an uneditable A or a genomically encoded G. The second CME site in the CME11 gene confers a “heterozygote advantage” during ascosporogenesis, meaning that concurrently expressing both edited and unedited versions is more advantageous than either.

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Why is it important?

This study demonstrates that conserved A-to-I editing sites are functionally important during development of complex multicellularity in fungi and provides the first experimental evidence for the long-suspected “heterozygote advantage” of RNA editing.