m6A RNA demethylase AtALKBH9B promotes mobilization of a heat-activated long terminal repeat retrotransposon in Arabidopsis

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, the roles of RNA methylation in transposon control remain unknown. Here, we suggest that transposon RNA is marked by m⁶A RNA methylation and is sequestered in stress granules (SGs) in an m⁶A-dependent manner. Intriguingly, SG-localized AtALKBH9B selectively demethylates a heat-activated retroelement, Onsen, 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.