Background Methylation of nucleotides, notably in the forms of 5-methylcytosine (5mC) in DNA and N 6 -methyladenosine (m 6 A) in mRNA, carries important information for gene regulation. 5mC has been elucidated to participate in the regulation of fruit ripening, whereas the function of m 6 A in this process and the interplay between 5mC and m 6 A remain uncharacterized. Results Here, we show that mRNA m 6 A methylation exhibits dynamic changes similar to DNA methylation during tomato fruit ripening. RNA methylome analysis reveals that m 6 A methylation is a prevalent modification in the mRNA of tomato fruit, and the m 6 A sites are enriched around the stop codons and within the 3′ untranslated regions. In the fruit of the ripening-deficient epimutant Colorless non-ripening ( Cnr ) which harbors DNA hypermethylation, over 1100 transcripts display increased m 6 A levels, while only 134 transcripts show decreased m 6 A enrichment, suggesting a global increase in m 6 A. The m 6 A deposition is generally negatively correlated with transcript abundance. Further analysis demonstrates that the overall increase in m 6 A methylation in Cnr mutant fruit is associated with the decreased expression of RNA demethylase gene SlALKBH2 , which is regulated by DNA methylation. Interestingly, SlALKBH2 has the ability to bind the transcript of SlDML2 , a DNA demethylase gene required for tomato fruit ripening, and modulates its stability via m 6 A demethylation. Mutation of SlALKBH2 decreases the abundance of SlDML2 mRNA and delays fruit ripening. Conclusions Our study identifies a novel layer of gene regulation for key ripening genes and establishes an essential molecular link between DNA methylation and mRNA m 6 A methylation during fruit ripening. Electronic supplementary material The online version of this article (10.1186/s13059-019-1771-7) contains supplementary material, which is available to authorized users.

Background Epigenetic mark such as DNA methylation plays pivotal roles in regulating ripening of both climacteric and non-climacteric fruits. However, it remains unclear whether mRNA m6A methylation, which has been shown to regulate ripening of the tomato, a typical climacteric fruit, is functionally conserved for ripening control among different types of fruits. Results Here we show that m6A methylation displays a dramatic change at ripening onset of strawberry, a classical non-climacteric fruit. The m6A modification in coding sequence (CDS) regions appears to be ripening-specific and tends to stabilize the mRNAs, whereas m6A around the stop codons and within the 3′ untranslated regions is generally negatively correlated with the abundance of associated mRNAs. We identified thousands of transcripts with m6A hypermethylation in the CDS regions, including those of NCED5, ABAR, and AREB1 in the abscisic acid (ABA) biosynthesis and signaling pathway. We demonstrate that the methyltransferases MTA and MTB are indispensable for normal ripening of strawberry fruit, and MTA-mediated m6A modification promotes mRNA stability of NCED5 and AREB1, while facilitating translation of ABAR. Conclusion Our findings uncover that m6A methylation regulates ripening of the non-climacteric strawberry fruit by targeting the ABA pathway, which is distinct from that in the climacteric tomato fruit.

The selective hydrodeoxygenation of lignin-derived guaiacol to value-added products, especially phenol, under relatively mild reaction conditions remains an important challenge. A Cl-modified Ru/TiO 2 catalyst exhibited higher phenol selectivity compared with an unmodified one in the conversion of guaiacol in 1,4-dioxane at 240 °C and 1 MPa H 2 . Unlike Ru/TiO 2 , the modified catalyst exhibited a modest activity of demethoxylation producing phenol but an inferior ability of hydrogenation of its aromatic ring, resulting in much slower consumption of phenol. The Cl species were likely localized at the metal−support interface and on the surface of metal particles, and these modified both Ru and Ti species electronically. It is presumed that electron-enriched Ru inhibits the ring hydrogenation reaction, and the defects on the TiO 2 surface promote the deoxygenation reaction.

Summary Dynamic chemical modifications in eukaryotic messenger RNAs (mRNAs) constitute an essential layer of gene regulation, among which N6‐methyladenosine (m6A) was unveiled to be the most abundant. m6A functionally modulates important biological processes in various mammals and plants through the regulation of mRNA metabolism, mainly mRNA degradation and translation efficiency. Physiological functions of m6A methylation are diversified and affected by intricate sequence contexts and m6A machineries. A number of studies have dissected the functional roles and the underlying mechanisms of m6A modifications in regulating plant development and stress responses. Recently, it was demonstrated that the human FTO‐mediated plant m6A removal caused dramatic yield increases in rice and potato, indicating that modulation of m6A methylation could be an efficient strategy for crop improvement. In this review, we summarize the current progress concerning the m6A‐mediated regulation of crop development and stress responses, and provide an outlook on the potential application of m6A epitranscriptome in the future improvement of crops.

The addition of Re to Ru/TiO2 could promote the reaction rate and product selectivity of n-C18H38via adjusting acid sites.

Epigenetic marks, such as DNA methylation, play pivotal roles in regulating ripening of both climacteric and non-climacteric fruits. However, it remains unclear whether mRNA m6A methylation, the epitranscriptome, is functionally conserved for ripening control. Here we show that m6A methylation, which has been revealed to regulate ripening of tomato, a typical climacteric fruit, displays a dramatic change at ripening onset of strawberry, a classical non-climacteric fruit. The m6A modification in the coding sequence (CDS) regions appears to be ripening-specific and tends to stabilize the mRNAs, whereas m6A around the stop codons and within the 3' untranslated regions is generally negatively correlated with the abundance of the mRNAs. We identified thousands of transcripts with m6A hypermethylation in the CDS regions, including those of NCED5, ABAR, and AREB1 in the abscisic acid (ABA) biosynthesis and signaling pathway. We demonstrated that the methyltransferases MTA and MTB are indispensable for normal ripening of strawberry fruit, and MTA-mediated m6A modification promotes mRNA stability of NCED5 and AREB1, while facilitates translation of ABAR.Our findings uncover that m6A methylation regulates ripening of non-climacteric strawberry fruit by targeting ABA pathway, which is distinct from that in climacteric tomato fruit.

BackgroundOligogalacturonic acids (OGs) are oligomers of alpha-1,4-linked galacturonosyl residues that are released from cell walls by the hydrolysis of polygalacturonic acids upon fruit ripening and under abiotic/biotic stress. OGs may induce ethylene production and fruit ripening, however, the mechanism(s) behind these processes is unknown.ResultsTomato cultivar ‘Ailsa Craig’ (AC) and mutant Neverripe, ripening inhibitor, non-ripening, and colorless non-ripening fruits were treated with OGs at different stages. Only AC fruits at mature green stage 1 showed an advanced ripening phenomenon, although transient ethylene production was detected in all of the tomato fruits. Ethylene synthesis genes LeACS2 and LeACO1 were rapidly up-regulated, and the phosphorylated LeACS2 protein was detected after OGs treatment. Protein kinase/phosphatase inhibitors significantly affected the ripening process induced by the OGs. As a potential receptor of OGs, LeWAKL2 was also up-regulated in their presence.ConclusionsWe demonstrated that OGs promoted tomato fruit ripening by inducing ethylene synthesis through the regulation of LeACS2 at transcriptional and post-translational levels.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0634-y) contains supplementary material, which is available to authorized users.

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