Methylations at position N of internal adenosines (mAs) are the most abundant and widespread mRNA modifications. These modifications play crucial roles in reproduction, growth, and development by controlling gene expression patterns at the posttranscriptional level. Their function is decoded by readers that share the YTH domain, which forms a hydrophobic pocket that directly accommodates the mA residues. While the physiological and molecular functions of YTH readers have been extensively studied in animals, little is known about plant readers, even though mAs are crucial for plant survival and development. Viridiplantae contains high numbers of YTH domain proteins. Here, we performed comprehensive evolutionary analysis of YTH domain proteins and demonstrated that they are highly likely to be actual readers with redundant as well as specific functions. We also show that the ECT2 protein from binds to mA-containing RNAs in vivo and that this property relies on the mA binding pocket carried by its YTH domain. ECT2 is cytoplasmic and relocates to stress granules upon heat exposure, suggesting that it controls mRNA fate in the cytosol. Finally, we demonstrate that ECT2 acts to decode the mA signal in the trichome and is required for their normal branching through controlling their ploidy levels.

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N6-Methyladenosine (m6A), one of the most abundant internal modification of eukaryotic mRNAs, participates in the post-transcriptional control of gene expression through recruitment of specific m6A readers. In Saccharomyces cerevisiae, the m6A methyltransferase Ime4 is expressed only during meiosis and its deletion impairs this process. To elucidate how m6A control gene expression, we investigated the function of the budding yeast m6A reader Pho92. We show that Pho92 is an early meiotic factor that promotes timely meiotic progression. High-throughput RNA sequencing and mapping of Pho92-binding sites following UV-crosslinking reveal that Pho92 is recruited to specific mRNAs in an m6A-dependent manner during the meiotic prophase, preceding their down-regulation. Strikingly, point mutations altering m6A sites in mRNAs targeted by Pho92 are sufficient to delay their down-regulation and, in one case, to slow down meiotic progression. Altogether, our results indicate that Pho92 facilitate the meiotic progression by accelerating the down-regulation of timely-regulated mRNAs during meiotic recombination.

N6-methyladenosine (m6A), the most abundant internal modification of eukaryotic mRNAs, participates in the post-transcriptional control of gene expression. In Saccharomyces cerevisiae, m6A is only found during meiosis. Although the deletion of the m6A-methyltransferase Ime4 impairs this process, the molecular impact of m6A on gene expression remains ill defined. Here we investigated the function of the budding yeast m6A reader Pho92. We found that Pho92 is specifically expressed during meiosis and impacts meiotic progression. We used high-throughput RNA sequencing and mapping of Pho92-binding sites following UV-crosslinking to show that Pho92 is recruited to specific mRNAs in an m6A-dependent manner during the meiotic prophase, preceding their down-regulation. Strikingly, point mutations altering m6A sites in mRNAs targeted by Pho92 are sufficient to delay their down-regulation and, in one case, to impact meiotic progression. Altogether, our results indicate that Pho92 facilitate the meiotic progression by accelerating the down-regulation of timely-regulated mRNAs during meiotic recombination.