m⁶A RNA demethylase AtALKBH9B promotes mobilization of a heat-activated long terminal repeat retrotransposon in <i>Arabidopsis</i>.

Abstract

Transposons are mobile and ubiquitous DNA molecules that can cause vast genomic alterations. In plants, it is well documented that transposon mobilization is strongly repressed by DNA methylation; however, its regulation at the posttranscriptional level remains relatively uninvestigated. Here, we suggest that transposon RNA is marked by m⁶A RNA methylation and can be localized in stress granules (SGs). Intriguingly, SG-localized AtALKBH9B selectively demethylates a heat-activated retroelement, <i>Onsen</i>, and thereby releases it from spatial confinement, allowing for its mobilization. In addition, we show evidence that m⁶A RNA methylation contributes to transpositional suppression by inhibiting virus-like particle assembly and extrachromosomal DNA production. In summary, this study unveils a previously unknown role for m⁶A in the suppression of transposon mobility and provides insight into how transposons counteract the m⁶A-mediated repression mechanism by hitchhiking the RNA demethylase of the host.