Unique features of the m⁶A methylome and its response to drought stress in sea buckthorn (<i>Hippophae rhamnoides</i> Linn.)

In plants, recent studies have revealed that N6-methyladenosine (m⁶A) methylation of mRNA has potential regulatory functions of this mRNA modification in many biological processes. m⁶A methyltransferase, m⁶A demethylase and m⁶A-binding proteins can cause differential phenotypes, indicating that m⁶A may have critical roles in the plant. In this study, we depicted the m⁶A map of sea buckthorn (<i>Hippophae rhamnoides</i> Linn.) transcriptome. Similar to <i>A. thaliana</i>, m⁶A sites of sea buckthorn transcriptome is significantly enriched around the stop codon and within 3ʹ-untranslated regions (3ʹUTR). Gene ontology analysis shows that the m⁶A modification genes are associated with metabolic biosynthesis. In addition, we identified 13,287 different m⁶A peaks (DMPs) between leaf under drought (TR) and control (CK) treatment. It reveals that m⁶A has a high level of conservation and has a positive correlation with mRNA abundance in plants. GO and KEGG enrichment results showed that DMP modification DEGs in TR were particularly associated with ABA biosynthesis. Interestingly, our results showed three m⁶A demethylase (<i>HrALKBH10B, HrALKBH10C</i> and <i>HrALKBH10D</i>) genes were significantly increased following drought stress, which indicated that it may contributed the decreased m⁶A levels. This exhaustive m⁶A map provides a basis and resource for the further functional study of mRNA m⁶A modification in abiotic stress.