Defining the commonalities between post-transcriptional and post-translational modification communities.

Post-transcriptional modifications of RNA (PRMs) and post-translational modifications of proteins (PTMs) are important regulatory mechanisms in biological processes and have many commonalities. However, the integration of these research areas is lacking. A recent discussion identified the priorities, areas of emphasis, and necessary technologies to advance and integrate these areas of study.

The covalent nucleotide modifications within plant mRNAs: What we know, how we find them, and what should be done in the future.

Although covalent nucleotide modifications were first identified on the bases of transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs), a number of these epitranscriptome marks have also been found to occur on the bases of messenger RNAs (mRNAs). These covalent mRNA features have been demonstrated to have various and significant effects on the processing (e.g. splicing, polyadenylation, etc.) and functionality (e.g. translation, transport, etc.) of these protein-encoding molecules. Here, we focus our attention on the current understanding of the collection of covalent nucleotide modifications known to occur on mRNAs in plants, how they are detected and studied, and the most outstanding future questions of each of these important epitranscriptomic regulatory signals.

Pathogen-induced m6A dynamics affect plant immunity.

Posttranscriptional regulation of mRNA mediated by methylation at the N6 position of adenine (N6-methyladenosine [m6A]) has profound effects on transcriptome regulation in plants. Focused studies across eukaryotes offer glimpses into the processes governed by m6A throughout developmental and disease states. However, we lack an understanding of the dynamics and the regulatory potential of m6A during biotic stress in plants. Here, we provide a comprehensive look into the effects of m6A on both the short-term and long-term responses to pathogen signaling in Arabidopsis (Arabidopsis thaliana). We demonstrate that m6A-deficient plants are more resistant to bacterial and fungal pathogen infections and have altered immune responses. Furthermore, m6A deposition is specifically coordinated on transcripts involved in defense and immunity prior to and proceeding the pathogen signal flagellin. Consequently, the dynamic modulation of m6A on specific stress-responsive transcripts is correlated with changes in abundance and cleavage of these transcripts. Overall, we show that the m6A methylome is regulated prior to and during simulated and active pathogen stress and functions in the coordination and balancing of normal growth and pathogen responses.

Transcription Is Just the Beginning of Gene Expression Regulation: The Functional Significance of RNA-Binding Proteins to Post-transcriptional Processes in Plants.

Plants have developed sophisticated mechanisms to compensate and respond to ever-changing environmental conditions. Research focus in this area has recently shifted towards understanding the post-transcriptional mechanisms that contribute to RNA transcript maturation, abundance and function as key regulatory steps in allowing plants to properly react and adapt to these never-ending shifts in their environments. At the center of these regulatory mechanisms are RNA-binding proteins (RBPs), the functional mediators of all post-transcriptional processes. In plants, RBPs are becoming increasingly appreciated as the critical modulators of core cellular processes during development and in response to environmental stimuli. With the majority of research on RBPs and their functions historically in prokaryotic and mammalian systems, it has more recently been unveiled that plants have expanded families of conserved and novel RBPs compared with their eukaryotic counterparts. To better understand the scope of RBPs in plants, we present past and current literature detailing specific roles of RBPs during stress response, development and other fundamental transition periods. In this review, we highlight examples of complex regulation coordinated by RBPs with a focus on the diverse mechanisms of plant RBPs and the unique processes they regulate. Additionally, we discuss the importance for additional research into understanding global interactions of RBPs on a systems and network-scale, with genome mining and annotation providing valuable insight for potential uses in improving crop plants in order to maintain high-level production in this era of global climate change.

The Diversity and Functions of Plant RNA Modifications: What We Know and Where We Go from Here.

Since the discovery of the first ribonucleic acid (RNA) modifications in transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs), scientists have been on a quest to decipher the identities and functions of RNA modifications in biological systems. The last decade has seen monumental growth in the number of studies that have characterized and assessed the functionalities of RNA modifications in the field of plant biology. Owing to these studies, we now categorize RNA modifications based on their chemical nature and the RNA on which they are found, as well as the array of proteins that are involved in the processes that add, read, and remove them from an RNA molecule. Beyond their identity, another key piece of the puzzle is the functional significance of the various types of RNA modifications. Here, we shed light on recent studies that help establish our current understanding of the diversity of RNA modifications found in plant transcriptomes and the functions they play at both the molecular (e.g., RNA stability, translation, and transport) and organismal (e.g., stress response and development) levels. Finally, we consider the key research questions related to plant gene expression and biology in general and highlight developments in various technologies that are driving our insights forward in this research area.

The fold makes all the difference in COOLAIR-mediated regulation of plant flowering time.

The secondary structure of an RNA molecule affects its regulation and function, but whether transcript isoforms adopt specific arrangements affecting their functionality is unclear. In a recent issue of Nature, Yang et al. reveal that the non-coding RNA COOLAIR can adopt isoform specific secondary structures that differentially regulate flowering.

Covalent RNA modifications and their budding crosstalk with plant epigenetic processes.

Our recent cognizance of diverse RNA classes undergoing dynamic covalent chemical modifications (or epitranscriptomic marks) in plants has provided fresh insight into the underlying molecular mechanisms of gene expression regulation. Comparatively, epigenetic marks comprising heritable modifications of DNA and histones have been extensively studied in plants and their impact on plant gene expression is quite established. Based on our growing knowledge of the plant epitranscriptome and epigenome, it is logical to explore how the two regulatory layers intermingle to intricately determine gene expression levels underlying key biological processes such as development and response to stress. Herein, we focus on the emerging evidence of crosstalk between the plant epitranscriptome with epigenetic regulation involving DNA modification, histone modification, and non-coding RNAs.

RNA biology takes root in plant systems.

Advances in RNA biology such as RNAi, CRISPR, and the first mRNA vaccine represent the enormous potential of RNA research to address current problems. Additionally, plants are a diverse and undeniably essential resource for life threatened by climate change, loss of arable land, and pollution. Different aspects of RNA such as its processing, modification and structure are intertwined with plant development, physiology and stress response. This report details the findings of researchers around the world during the 23rd Penn State Symposium in Plant Biology with a focus in RNA biology.

TRIM11 Prevents and Reverses Protein Aggregation and Rescues a Mouse Model of Parkinson's Disease.

Neurodegenerative diseases are characterized by the formation and propagation of protein aggregates, especially amyloid fibrils. However, what normally suppresses protein misfolding and aggregation in metazoan cells remains incompletely understood. Here, we show that TRIM11, a member of the metazoan tripartite motif (TRIM) family, both prevents the formation of protein aggregates and dissolves pre-existing protein deposits, including amyloid fibrils. These molecular chaperone and disaggregase activities are ATP independent. They enhance folding and solubility of normal proteins and cooperate with TRIM11 SUMO ligase activity to degrade aberrant proteins. TRIM11 abrogates α-synuclein fibrillization and restores viability in cell models of Parkinson's disease (PD). Intracranial adeno-associated viral delivery of TRIM11 mitigates α-synuclein-mediated pathology, neurodegeneration, and motor impairments in a PD mouse model. Other TRIMs can also function as ATP-independent molecular chaperones and disaggregases. Thus, we define TRIMs as a potent and multifunctional protein quality-control system in metazoa, which might be applied to treat neurodegenerative diseases.

Assays for the Degradation of Misfolded Proteins in Cells.

Protein misfolding and aggregation are associated with various neurodegenerative diseases. Cellular mechanisms that recognize and degrade misfolded proteins may serve as potential therapeutic targets. To distinguish degradation of misfolding-prone proteins from other mechanisms that regulate their levels, one important method is to measure protein half-life in cells. However, this can be challenging because misfolding-prone proteins may exist in different forms, including the native form and misfolded forms of distinct characteristics. Here we describe assays to examine the half-life of misfolded proteins in mammalian cells using a highly aggregation-prone protein, Ataxin-1 with an extended polyglutamine (polyQ) stretch, and a conformationally unstable luciferase mutant as models. Cycloheximide chase is combined with cell fractionation to examine the turnover rate of misfolding-prone proteins in various cellular fractions. We further depict a fluorescence-based assay using an enhanced green fluorescence protein (EGFP)-fusion of the luciferase mutant, which can be adapted for high throughput screening on a microplate-reader.

Utility of a Phylogenetic Perspective in Structural Analysis of CYP72A Enzymes from Flowering Plants.

Plant adaptation to external pressures depends on functional diversity in cytochrome P450 (CYP) enzymes. CYPs contain structural domains necessary for the characteristic P450 fold that allows monooxygenation, but they also have great variation in substrate binding affinity. Plant genomes typically contain hundreds of CYPs that contribute to essential functions and species-specific metabolism. The CYP72A subfamily is conserved in angiosperms but its contribution to physiological functions is largely unknown. With genomic information available for many plants, a focused analysis of CYP subfamily diversity is important to understand the contributions of these enzymes to plant evolution. This study examines the extent to which independent gene duplication and evolution have contributed to structural diversification of CYP72A enzymes in different plant lineages. CYP72A genes are prevalent across angiosperms, but the number of genes within each genome varies greatly. The prevalence of CYP72As suggest that the last common ancestor of flowering plants contained a CYP72A sequence, but gene duplication and retention has varied greatly for this CYP subfamily. Sequence comparisons show that CYP72As are involved in species-specific metabolic functions in some plants while there is likely functional conservation between closely related species. Analysis of structural and functional domains within groups of CYP72As reveals clade-specific residues that contribute to functional constraints within subsets of CYP72As. This study provides a phylogenetic framework that allows comparisons of structural features within subsets of the CYP72A subfamily. We examined a large number of sequences from a broad collection of plant species to detect patterns of functional conservation across the subfamily. The evolutionary relationships between CYPs in plant genomes are an important component in understanding the evolution of biochemical diversity in plants.