mRNA ADENOSINE METHYLASE promotes drought tolerance through N6-methyladenosine-dependent and independent impacts on mRNA regulation in Arabidopsis

• Among many mRNA modifications, adenine methylation at the N6 position (N6-methyladenosine, m6A) is known to affect mRNA biology extensively. The influence of m6A has yet to be assessed under drought, one of the most impactful abiotic stresses. • We show that Arabidopsis thaliana (L.) Heynh. (Arabidopsis) plants lacking mRNA ADENOSINE METHYLASE (MTA) are drought sensitive. Subsequently, we comprehensively assess the impacts of MTA-dependent m6A changes during drought on mRNA abundance, stability, and translation in Arabidopsis. • During drought, there is a global trend towards hyper-methylation of many protein-coding transcripts that does not occur in mta. We also observe complex regulation of m6A at a transcript-specific level, possibly reflecting compensation by other m6A components. Importantly, a subset of transcripts that are hyper-methylated in an MTA-dependent manner exhibited reduced turnover and translation in mta, compared to wild-type plants, during drought. Additionally, MTA impacts transcript stability and translation independently of m6A. We also correlate drought-associated deposition of m6A with increased translation of modulators of drought response, such as RD29A, COR47, COR413, ALDH2B, ERD7, and ABF4 in WT, which is impaired in mta. • m6A is dynamic during drought and, alongside MTA, promotes tolerance by regulating drought-responsive changes in transcript turnover and translation. Arabidopsis Col-0 (WT) and a line with embryo-specific expression of MTA (proABI3:MTA/mta) were exposed to a 12-day drought and leaf tissue was profiled with mRNA-seq, GMUCT, polysomal RNA-seq, and m6A-RIP-seq.