The m6A reader ECT8 is an abiotic stress sensor that accelerates mRNA decay in Arabidopsis.

N 6-methyladenosine (m6A) is the most abundant mRNA modification and plays diverse roles in eukaryotes, including plants. It regulates various processes, including plant growth, development, and responses to external or internal stress responses. However, the mechanisms underlying how m6A is related to environmental stresses in both mammals and plants remain elusive. Here, we identified EVOLUTIONARILY CONSERVED C-TERMINAL REGION 8 (ECT8) as an m6A reader protein and showed that its m6A-binding capability is required for salt stress responses in Arabidopsis (Arabidopsis thaliana). ECT8 accelerates the degradation of its target transcripts through direct interaction with the decapping protein DECAPPING 5 within processing bodies. We observed a significant increase in the ECT8 expression level under various environmental stresses. Using salt stress as a representative stressor, we found that the transcript and protein levels of ECT8 rise in response to salt stress. The increased abundance of ECT8 protein results in the enhanced binding capability to m6A-modified mRNAs, thereby accelerating their degradation, especially those of negative regulators of salt stress responses. Our results demonstrated that ECT8 acts as an abiotic stress sensor, facilitating mRNA decay, which is vital for maintaining transcriptome homeostasis and enhancing stress tolerance in plants. Our findings not only advance the understanding of epitranscriptomic gene regulation but also offer potential applications for breeding more resilient crops in the face of rapidly changing environmental conditions.

The m6A reader SlYTH2 negatively regulates tomato fruit aroma by impeding the translation process.

N6-methyladenosine (m6A) is a fundamentally important RNA modification for gene regulation, whose function is achieved through m6A readers. However, whether and how m6A readers play regulatory roles during fruit ripening and quality formation remains unclear. Here, we characterized SlYTH2 as a tomato m6A reader protein and profiled the binding sites of SlYTH2 at the transcriptome-wide level. SlYTH2 undergoes liquid-liquid phase separation and promotes RNA-protein condensate formation. The target mRNAs of SlYTH2, namely m6A-modified SlHPL and SlCCD1B associated with volatile synthesis, are enriched in SlYTH2-induced condensates. Through polysome profiling assays and proteomic analysis, we demonstrate that knockout of SlYTH2 expedites the translation process of SlHPL and SlCCD1B, resulting in augmented production of aroma-associated volatiles. This aroma enrichment significantly increased consumer preferences for CRISPR-edited fruit over wild type. These findings shed light on the underlying mechanisms of m6A in plant RNA metabolism and provided a promising strategy to generate fruits that are more attractive to consumers.

Principles, functions, and biological implications of m6A in plants.

Over the past decade, N 6-methyladenosine (m6A) has emerged as a prevalent and dynamically regulated modification across the transcriptome; it has been reversibly installed, removed, and interpreted by specific binding proteins, and has played crucial roles in molecular and biological processes. Within this scope, we consolidate recent advancements of m6A research in plants regarding gene expression regulation, diverse physiologic and pathogenic processes, as well as crop trial implications, to guide discussions on challenges associated with and leveraging epitranscriptome editing for crop improvement.

FIONA1-mediated methylation of the 3'UTR of FLC affects FLC transcript levels and flowering in Arabidopsis.

Adenosine bases of RNA can be transiently modified by the deposition of a methyl-group to form N6-methyladenosine (m6A). This adenosine-methylation is an ancient process and the enzymes involved are evolutionary highly conserved. A genetic screen designed to identify suppressors of late flowering transgenic Arabidopsis plants overexpressing the miP1a microProtein yielded a new allele of the FIONA1 (FIO1) m6A-methyltransferase. To characterize the early flowering phenotype of fio1 mutant plants we employed an integrative approach of mRNA-seq, Nanopore direct RNA-sequencing and meRIP-seq to identify differentially expressed transcripts as well as differentially methylated RNAs. We provide evidence that FIO1 is the elusive methyltransferase responsible for the 3'-end methylation of the FLOWERING LOCUS C (FLC) transcript. Furthermore, our genetic and biochemical data suggest that 3'-methylation stabilizes FLC mRNAs and non-methylated FLC is a target for rapid degradation.

Methyltransferase ATMETTL5 writes m6A on 18S ribosomal RNA to regulate translation in Arabidopsis.

Aberrant RNA modifications can lead to dysregulated gene expression and impeded growth in plants. Ribosomal RNA (rRNA) constitutes a substantial portion of total RNA, while the precise functions and molecular mechanisms underlying rRNA modifications in plants remain largely elusive. Here, we elucidated the exclusive occurrence of the canonical RNA modification N6-methyladenosine (m6A) solely 18S rRNA, but not 25S rRNA. We identified a completely uncharacterized protein, ATMETTL5, as an Arabidopsis m6A methyltransferase responsible for installing m6A methylation at the 1771 site of the 18S rRNA. ATMETTL5 is ubiquitously expressed and localized in both nucleus and cytoplasm, mediating rRNA m6A methylation. Mechanistically, the loss of ATMETTL5-mediated methylation results in attenuated translation. Furthermore, we uncovered the role of ATMETTL5-mediated methylation in coordinating blue light-mediated hypocotyl growth by regulating the translation of blue light-related messenger RNAs (mRNAs), specifically HYH and PRR9. Our findings provide mechanistic insights into how rRNA modification regulates ribosome function in mRNA translation and the response to blue light, thereby advancing our understanding of the role of epigenetic modifications in precisely regulating mRNA translation in plants.

The m6A Reader ECT2 Controls Trichome Morphology by Affecting mRNA Stability in Arabidopsis.

The epitranscriptomic mark N6-methyladenosine (m6A) can be written, read, and erased via the action of a complex network of proteins. m6A binding proteins read m6A marks and transduce their downstream regulatory effects by altering RNA metabolic processes. The characterization of m6A readers is an essential prerequisite for understanding the roles of m6A in plants, but the identities of m6A readers have been unclear. Here, we characterized the YTH-domain family protein ECT2 as an Arabidopsis thaliana m6A reader whose m6A binding function is required for normal trichome morphology. We developed the formaldehyde cross-linking and immunoprecipitation method to identify ECT2-RNA interaction sites at the transcriptome-wide level. This analysis demonstrated that ECT2 binding sites are strongly enriched in the 3' untranslated regions (3' UTRs) of target genes and led to the identification of a plant-specific m6A motif. Sequencing analysis suggested that ECT2 plays dual roles in regulating 3' UTR processing in the nucleus and facilitating mRNA stability in the cytoplasm. Disruption of ECT2 accelerated the degradation of three ECT2 binding transcripts related to trichome morphogenesis, thereby affecting trichome branching. The results shed light on the underlying mechanisms of the roles of m6A in RNA metabolism, as well as plant development and physiology.

RNA methylation in mammalian development and cancer.

Similar to epigenetic DNA and histone modifications, epitranscriptomic modifications (RNA modifications) have emerged as crucial regulators in temporal and spatial gene expression during eukaryotic development. To date, over 170 diverse types of chemical modifications have been identified upon RNA nucleobases. Some of these post-synthesized modifications can be reversibly installed, removed, and decoded by their specific cellular components and play critical roles in different biological processes. Accordingly, dysregulation of RNA modification effectors is tightly orchestrated with developmental processes. Here, we particularly focus on three well-studied RNA modifications, including N6-methyladenosine (m6A), 5-methylcytosine (m5C), and N1-methyladenosine (m1A), and summarize recent knowledge of underlying mechanisms and critical roles of these RNA modifications in stem cell fate determination, embryonic development, and cancer progression, providing a better understanding of the whole association between epitranscriptomic regulation and mammalian development.

Mendelian randomization study on the causal relationship between food and cholelithiasis.

Background: Cholelithiasis, commonly referred to as gallstones, is a prevalent medical condition influenced by a combination of genetic factors, lifestyle choices, and dietary habits. Specific food items have been associated with an increased susceptibility to cholelithiasis, whereas others seem to offer a protective effect against its development. Methods: In this study, we conducted a Mendelian randomization (MR) analysis using a large-scale genetic dataset comprising individuals with European ancestry to explore the potential causal relationship between diet and cholelithiasis. The analysis incorporated 17 food-related variables, which were considered as potential factors influencing the occurrence of this condition. Results: Our findings indicate that a higher consumption of cooked vegetables, dried fruit, and oily fish is associated with a reduced risk of cholelithiasis. Conversely, a higher consumption of lamb is associated with an increased risk of developing the condition. Importantly, these associations proved robust to sensitivity and heterogeneity tests, and the pleiotropic test results further supported the hypothesis of a causal relationship between diet and cholelithiasis. Conclusion: Through our study, we provide compelling evidence for the existence of a causal relationship between diet and cholelithiasis. Adopting a dietary pattern enriched with cooked vegetables, dried fruit, and oily fish, while minimizing lamb intake, may contribute to the prevention of cholelithiasis. Recognizing diet as a modifiable risk factor in the prevention and management of this condition is of paramount importance, and our study offers valuable insights in this regard.

C2-methyladenosine in tRNA promotes protein translation by facilitating the decoding of tandem m2A-tRNA-dependent codons.

RNA modification C2-methyladenosine (m2A) exists in both rRNA and tRNA of Escherichia coli (E. coli), installed by the methyltransferase RlmN using a radical-S-adenosylmethionine (SAM) mechanism. However, the precise function of m2A in tRNA and its ubiquity in plants have remained unclear. Here we discover the presence of m2A in chloroplast rRNA and tRNA, as well as cytosolic tRNA, in multiple plant species. We identify six m2A-modified chloroplast tRNAs and two m2A-modified cytosolic tRNAs across different plants. Furthermore, we characterize three Arabidopsis m2A methyltransferases-RLMNL1, RLMNL2, and RLMNL3-which methylate chloroplast rRNA, chloroplast tRNA, and cytosolic tRNA, respectively. Our findings demonstrate that m2A37 promotes a relaxed conformation of tRNA, enhancing translation efficiency in chloroplast and cytosol by facilitating decoding of tandem m2A-tRNA-dependent codons. This study provides insights into the molecular function and biological significance of m2A, uncovering a layer of translation regulation in plants.

The RNA binding protein EHD6 recruits the m6A reader YTH07 and sequesters OsCOL4 mRNA into phase-separated ribonucleoprotein condensates to promote rice flowering.

N6-Methyladenosine (m6A) is one of the most abundant modifications of eukaryotic mRNA, but its comprehensive biological functionality remains further exploration. In this study, we identified and characterized a new flowering-promoting gene, EARLY HEADING DATE6 (EHD6), in rice. EHD6 encodes an RNA recognition motif (RRM)-containing RNA binding protein that is localized in the non-membranous cytoplasm ribonucleoprotein (RNP) granules and can bind both m6A-modified RNA and unmodified RNA indiscriminately. We found that EHD6 can physically interact with YTH07, a YTH (YT521-B homology) domain-containing m6A reader. We showed that their interaction enhances the binding of an m6A-modified RNA and triggers relocation of a portion of YTH07 from the cytoplasm into RNP granules through phase-separated condensation. Within these condensates, the mRNA of a rice flowering repressor, CONSTANS-like 4 (OsCOL4), becomes sequestered, leading to a reduction in its protein abundance and thus accelerated flowering through the Early heading date 1 pathway. Taken together, these results not only shed new light on the molecular mechanism of efficient m6A recognition by the collaboration between an RNA binding protein and YTH family m6A reader, but also uncover the potential for m6A-mediated translation regulation through phase-separated ribonucleoprotein condensation in rice.

Colorectal cancer therapy mediated by nanomedicines.

Colorectal cancer is the third most malignant gastrointestinal tumor. Although traditional chemotherapy and radiotherapy have been widely used for treating colorectal cancer, the treatment effect is still unsatisfactory, resulting in a high mortality rate and a low 5-year survival rate. In recent years, with the development of molecular biology of colorectal cancer, many promising therapeutic strategies based on nanomaterials have been developed for colorectal cancer. In this review, we focus on recent advances in colorectal cancer treatment-related nanomedicines. We first discuss the exploration of stimuli-responsive drug delivery systems (DDSs) for colorectal cancer treatment using pH, hypoxia, glutathione (GSH), enzymes, light, magnetic fields (MF), and ultrasound (US) as stimuli. Moreover, the latest progress in emerging therapy for colorectal cancer is further summarized, including photothermal therapy (PTT), magnetothermal therapy (MTT), photodynamic therapy (PDT), sonodynamic therapy (SDT), and chemodynamic therapy (CDT). Finally, we explore the existing challenges and future directions for the better design and development of nanomedicines for clinical colorectal cancer treatment.

Multifunctional biocompatible Ni/Ni-P nanospheres for anti-tumor "neoadjuvant phototherapy" combining photothermal therapy and photodynamic therapy.

Gastric cancer, a gastrointestinal tumor with high morbidity and lethality, is often treated using strategies that are not as effective as they could be due to the locally advanced stage. Although pre-operative neoadjuvant chemotherapy can degrade the tumor stage to afford the possibility of surgery, it still possesses the problems of high systemic toxicity and low selectivity. In this work, we constructed an intelligent multi-functional nanoplatform (NNPIP NPs) with synergistic effects of photothermal therapy (PTT) and photodynamic therapy (PDT), which consisted of the nickel/nickel phosphide (Ni/Ni-P) nanosphere as the core, polyethyleneimine (PEI) as the shell, and the loaded indocyanine green (ICG). The mutual reinforcement of heat generated by the core and photosensitizer under 808 nm NIR laser irradiation is highly effective in the synergistic action of PTT. And co-delivery of ICG with nanoparticles into the cell enhances the PDT effect by reducing the consumption of singlet oxygen (1O2). Ultimately, this therapeutic strategy in vivo not only shrunk tumors but even eliminated tumors completely in a quarter of samples, which may be considered as a potential alternative to neoadjuvant chemotherapy and called "neoadjuvant phototherapy". In addition, as a nanoplatform based on transition metal nickel, NNPIP NPs could also be considered as a potential contrast agent for T1-weighted magnetic resonance imaging (MRI). Herein, we can diagnose and achieve pre-surgical downstaging of tumors and hope to improve R0 resection rates with lower toxicity and higher selectivity.

m6A readers ECT2/ECT3/ECT4 enhance mRNA stability through direct recruitment of the poly(A) binding proteins in Arabidopsis.

BACKGROUND: RNA N6-methyladenosine (m6A) modification is critical for plant growth and crop yield. m6A reader proteins can recognize m6A modifications to facilitate the functions of m6A in gene regulation. ECT2, ECT3, and ECT4 are m6A readers that are known to redundantly regulate trichome branching and leaf growth, but their molecular functions remain unclear. RESULTS: Here, we show that ECT2, ECT3, and ECT4 directly interact with each other in the cytoplasm and perform genetically redundant functions in abscisic acid (ABA) response regulation during seed germination and post-germination growth. We reveal that ECT2/ECT3/ECT4 promote the stabilization of their targeted m6A-modified mRNAs, but have no function in alternative polyadenylation and translation. We find that ECT2 directly interacts with the poly(A) binding proteins, PAB2 and PAB4, and maintains the stabilization of m6A-modified mRNAs. Disruption of ECT2/ECT3/ECT4 destabilizes mRNAs of ABA signaling-related genes, thereby promoting the accumulation of ABI5 and leading to ABA hypersensitivity. CONCLUSION: Our study reveals a unified functional model of m6A mediated by m6A readers in plants. In this model, ECT2/ECT3/ECT4 promote stabilization of their target mRNAs in the cytoplasm.

FIONA1 is an RNA N6-methyladenosine methyltransferase affecting Arabidopsis photomorphogenesis and flowering.

BACKGROUND: N6-methyladenosine (m6A) mRNA modification is essential for mammalian and plant viability. The U6 m6A methyltransferases in other species regulate S-adenosylmethionine (SAM) homeostasis through installing m6A in pre-mRNAs of SAM synthetases. However, U6 m6A methyltransferase has not been characterized in Arabidopsis and little is known about its role in regulating photomorphogenesis and flowering. RESULTS: Here we characterize that FIONA1 is an Arabidopsis U6 m6A methyltransferase that installs m6A in U6 snRNA and a small subset of poly(A)+ RNA. Disruption of FIONA1 leads to phytochrome signaling-dependent hypocotyl elongation and photoperiod-independent early flowering. Distinct from mammalian METTL16 and worm METT-10, FIONA1 neither installs m6A in the mRNAs of Arabidopsis SAM synthetases nor affects their transcript expression levels under normal or high SAM conditions. We confirm that FIONA1 can methylate plant mRNA m6A motifs in vitro and in vivo. We further show that FIONA1 installs m6A in several phenotypic related transcripts, thereby affecting downstream mRNA stability and regulating phytochrome signaling and floral transition. CONCLUSION: FIONA1 is functional as a U6 m6A methyltransferase in Arabidopsis, distinct from mammalian METTL16 and worm METT-10. Our results demonstrate that FIONA1-mediated m6A post-transcriptional regulation is an autonomous regulator for flowering and phytochrome signaling-dependent photomorphogenesis.

Arabidopsis N6-methyladenosine reader CPSF30-L recognizes FUE signals to control polyadenylation site choice in liquid-like nuclear bodies.

The biological functions of the epitranscriptomic modification N6-methyladenosine (m6A) in plants are not fully understood. CPSF30-L is a predominant isoform of the polyadenylation factor CPSF30 and consists of CPSF30-S and an m6A-binding YTH domain. Little is known about the biological roles of CPSF30-L and the molecular mechanism underlying its m6A-binding function in alternative polyadenylation. Here, we characterized CPSF30-L as an Arabidopsis m6A reader whose m6A-binding function is required for the floral transition and abscisic acid (ABA) response. We found that the m6A-binding activity of CPSF30-L enhances the formation of liquid-like nuclear bodies, where CPSF30-L mainly recognizes m6A-modified far-upstream elements to control polyadenylation site choice. Deficiency of CPSF30-L lengthens the 3' untranslated region of three phenotypes-related transcripts, thereby accelerating their mRNA degradation and leading to late flowering and ABA hypersensitivity. Collectively, this study uncovers a new molecular mechanism for m6A-driven phase separation and polyadenylation in plants.

RNA demethylation increases the yield and biomass of rice and potato plants in field trials.

RNA N6-methyladenosine (m6A) modifications are essential in plants. Here, we show that transgenic expression of the human RNA demethylase FTO in rice caused a more than threefold increase in grain yield under greenhouse conditions. In field trials, transgenic expression of FTO in rice and potato caused ~50% increases in yield and biomass. We demonstrate that the presence of FTO stimulates root meristem cell proliferation and tiller bud formation and promotes photosynthetic efficiency and drought tolerance but has no effect on mature cell size, shoot meristem cell proliferation, root diameter, plant height or ploidy. FTO mediates substantial m6A demethylation (around 7% of demethylation in poly(A) RNA and around 35% decrease of m6A in non-ribosomal nuclear RNA) in plant RNA, inducing chromatin openness and transcriptional activation. Therefore, modulation of plant RNA m6A methylation is a promising strategy to dramatically improve plant growth and crop yield.