Transcriptome analysis reveals molecular mechanisms underlying chloroplast biogenesis in albino Agave angustifolia plantlets.

Albino plants display partial or complete loss of photosynthetic pigments and defective thylakoid membrane development, consequently impairing plastid function and development. These distinctive attributes render albino plants excellent models for investigating chloroplast biogenesis. Despite their potential, limited exploration has been conducted regarding the molecular alterations underlying these phenotypes, extending beyond photosynthetic metabolism. In this study, we present a novel de novo transcriptome assembly of an albino somaclonal variant of Agave angustifolia Haw., which spontaneously emerged during the micropropagation of green plantlets. Additionally, RT-qPCR analysis was employed to validate the expression of genes associated with chloroplast biogenesis, and plastome copy numbers were quantified. This research aims to gain insight into the molecular disruptions affecting chloroplast development and ascertain whether the expression of critical genes involved in plastid development and differentiation is compromised in albino tissues of A. angustifolia. Our transcriptomic findings suggest that albino Agave plastids exhibit high proliferation, activation of the protein import machinery, altered transcription directed by PEP and NEP, dysregulation of plastome expression genes, reduced expression of photosynthesis-associated nuclear genes, disruption in the tetrapyrrole and carotenoid biosynthesis pathway, alterations in the plastid ribosome, and an increased number of plastome copies, among other alterations.

Picky eaters: selective autophagy in plant cells.

Autophagy, a fundamental cellular process, plays a vital role in maintaining cellular homeostasis by degrading damaged or unnecessary components. While selective autophagy has been extensively studied in animal cells, its significance in plant cells has only recently gained attention. In this review, we delve into the intriguing realm selective autophagy in plants, with specific focus on its involvement in nutrient recycling, organelle turnover, and stress response. Moreover, recent studies have unveiled the interesting interplay between selective autophagy and epigenetic mechanisms in plants, elucidating the significance of epigenetic regulation in modulating autophagy-related gene expression and finely tuning the selective autophagy process in plants. By synthesizing existing knowledge, this review highlights the emerging field of selective autophagy in plant cells, emphasizing its pivotal role in maintaining nutrient homeostasis, facilitating cellular adaptation, and shedding light on the epigenetic regulation that governs these processes. Our comprehensive study provides the way for a deeper understanding of the dynamic control of cellular responses to nutrient availability and stress conditions, opening new avenues for future research in this field of autophagy in plant physiology.

Epigenetic Regulation in Heterosis and Environmental Stress: The Challenge of Producing Hybrid Epigenomes to Face Climate Change.

Epigenetic regulation has the potential to revolutionize plant breeding and improve crop yields by regulating gene expression in plants. DNA methylation and histone modifications are key epigenetic modifications that can impact plant development, stress responses, productivity, and yields. Higher-yielding crops not only generate greater profits for farmers and seed producers, but also require less land, water, fuel, and fertilizer than traditional crops for equivalent yields. The use of heterosis in crops can influence productivity and food quality, but producing hybrids with superior agronomic traits to their parents remains challenging. However, epigenetic markers, such as histone methylation and acetylation, may help select parental and hybrid combinations with better performances than the parental plants. This review assesses the potential applications of epigenetics in crop breeding and improvement, rendering agriculture more efficient, sustainable, and adaptable to changing environmental conditions.

Physiological, epigenetic, and proteomic responses in Pfaffia glomerata growth in vitro under salt stress and 5-azacytidine.

Plants adjust their complex molecular, biochemical, and metabolic processes to overcome salt stress. Here, we investigated the proteomic and epigenetic alterations involved in the morphophysiological responses of Pfaffia glomerata, a medicinal plant, to salt stress and the demethylating agent 5-azacytidine (5-azaC). Moreover, we investigated how these changes affected the biosynthesis of 20-hydroxyecdysone (20-E), a pharmacologically important specialized metabolite. Plants were cultivated in vitro for 40 days in Murashige and Skoog medium supplemented with NaCl (50 mM), 5-azaC (25 µM), and NaCl + 5-azaC. Compared with the control (medium only), the treatments reduced growth, photosynthetic rates, and photosynthetic pigment content, with increase in sucrose, total amino acids, and proline contents, but a reduction in starch and protein. Comparative proteomic analysis revealed 282 common differentially accumulated proteins involved in 87 metabolic pathways, most of them related to amino acid and carbohydrate metabolism, and specialized metabolism. 5-azaC and NaCl + 5-azaC lowered global DNA methylation levels and 20-E content, suggesting that 20-E biosynthesis may be regulated by epigenetic mechanisms. Moreover, downregulation of a key protein in jasmonate biosynthesis indicates the fundamental role of this hormone in the 20-E biosynthesis. Taken together, our results highlight possible regulatory proteins and epigenetic changes related to salt stress tolerance and 20-E biosynthesis in P. glomerata, paving the way for future studies of the mechanisms involved in this regulation.

Same modification, different location: the mythical role of N6-adenine methylation in plant genomes.

MAIN CONCLUSION: The present review summarizes recent advances in the understanding of 6mA in DNA as an emergent epigenetic mark with distinctive characteristics, discusses its importance in plant genomes, and highlights its chemical nature and functions. Adenine methylation is an epigenetic modification present in DNA (6mA) and RNA (m6A) that has a regulatory function in many cellular processes. This modification occurs through a reversible reaction that covalently binds a methyl group, usually at the N6 position of the purine ring. This modification carries biophysical properties that affect the stability of nucleic acids as well as their binding affinity with other molecules. DNA 6mA has been related to genome stability, gene expression, DNA replication, and repair mechanisms. Recent advances have shown that 6mA in plant genomes is related to development and stress response. In this review, we present recent advances in the understanding of 6mA in DNA as an emergent epigenetic mark with distinctive characteristics. We discuss the key elements of this modification, focusing mainly on its importance in plant genomes. Furthermore, we highlight its chemical nature and the regulatory effects that it exerts on gene expression and plant development. Finally, we emphasize the functions of 6mA in photosynthesis, stress, and flowering.

Effects on the Post-translational Modification of H3K4Me3, H3K9ac, H3K9Me2, H3K27Me3, and H3K36Me2 Levels in Cerebral Cortex, Hypothalamus and Pons of Rats after a Systemic Administration of Cannabidiol: A Preliminary Study.

BACKGROUND: Cannabidiol (CBD), a non-psychotropic constituent of Cannabis sativa, has shown therapeutic promises by modulating several pathological conditions, including pain, epilepsy autism, among others. However, the molecular mechanism of action of CBD remains unknown and recent data suggest the engagement on CBD´s effects of nuclear elements, such as histone activity. AIM: This study assessed the changes in the post-translational modification (PTM) on the histones H3K4Me3, H3K9ac, H3K9Me2, H3K27Me3, and H3K36Me2 in several brain regions of rats after the administration of CBD (20 mg/Kg/i.p.). OBJECTIVE: To evaluate the effects on the PTM of histones H3K4Me3, H3K9ac, H3K9Me2, H3K27Me3, and H3K36Me2 levels in the cerebral cortex, hypothalamus and pons of CBD-treated rats. METHODS: Ten adult rats were randomly assigned into 2 groups: Control or CBD (20 mg/Kg/i.p). Animals were sacrificed after treatments and brains were collected for dissections of the cerebral cortex, hypothalamus and pons. Samples were analyzed for PTM on the histones H3K4Me3, H3K9ac, H3K9Me2, H3K27Me3, and H3K36Me2 levels by Western blot procedure. RESULTS: CBD increased the PTM levels on the histones H3K4Me3, H3K9ac, and H3K27Me3 in the cerebral cortex whereas no significant differences were found in H3K9Me2 and H3K36Me2. In addition, in the hypothalamus, CBD decreased the contents of H3K9ac while no significant effects were observed in H3K4Me3, H3K9Me2, H3K27Me3, and H3K36Me2. Lastly, in the pons, CBD- treated rats showed a significant decline on the PTM levels of H3K4Me3 whereas no statistical differences were found in H3K9ac, H3K9Me2, H3K27Me3, and H3K36Me2. CONCLUSION: The study showed that CBD induced differential effects in levels of PTM on the histones H3K4Me3, H3K9ac, H3K9Me2, H3K27Me3, and H3K36Me2 in several brain regions.

Auxins, the hidden player in chloroplast development.

Throughout decades of plant research, the plant hormones known as auxins have been found to be of vital importance in most plant development processes. Indole-3-acetic acid (IAA) represents the most common auxin in plants and can be synthesized from its tryptophan precursor, which is synthesized in the chloroplast. The chloroplast constitutes an organelle of great relevance to plants since the photosynthesis process by which plants get most of their energy is carried out there. The role of auxins in photosynthesis has been studied for at least 50 years, and in this time, it has been shown that auxins have an effect on several of the essential components and structure of the chloroplast. In recent decades, a high number of genes have been reported to be expressed in the chloroplast and some of their mutants have been shown to alter different auxin-mediated pathways. Genes in signaling pathways such as IAA/AUX, ARF, GH.3, SAUR and TIR, biosynthesis-related genes such as YUCCA and transport-related genes such as PIN have been identified among the most regulated genes in mutants related to alterations in the chloroplast. This review aims to provide a complete and updated summary of the relationship between auxins and several processes that involve the chloroplast, including chloroplast development, plant albinism, redox regulation and pigment synthesis.

A peak in global DNA methylation is a key step to initiate the somatic embryogenesis of coconut palm (Cocos nucifera L).

KEY MESSAGE: DNA methylation, morphogenesis and gene expression during the somatic embryogenesis of Coconut are affected by 5-Azacytidine pretreatments, indicating that DNA methylation is an important factor throughout this process. Somatic embryogenesis (SE) is a process that can aid in the production of elite Cocos nucifera palms. It has been well established that epigenetic mechanisms are regulators of cell differentiation programs; however, their role in the coconut somatic embryogenesis has not yet been addressed. To this end, the morphogenetic changes, the global DNA methylation and the expression profiles of the SE-related genes and DNA methyltransferases genes were evaluated during the SE process, with and without the presence of 5-Azacytidine (AzaC). The results show that three days of pretreatments with 15 µM and 20 µM of AzaC significantly increased early somatic embryo formation (four- and tenfold, respectively). A clear peak of the global percentage of DNA methylation (approximately 13%) was determined at the beginning of the culture, followed by a re-establishing stage and a steady increase thereafter; in all cases, the levels of DNA methylation were lower after the pretreatments with AzaC. Additionally, the expression profiles of the SERK, WUS, BBM and LEC genes are modulated during the SE process and the pretreatments with AzaC affect the expression profiles of these genes, even at early stages. Furthermore, increased levels of expression were observed for the genes encoding for DNA methyltransferases (MET, CMT and DRM) at early and late stages of SE, indicating that DNA methylation is an important factor throughout the SE.

Auxin perception in Agave is dependent on the species' Auxin Response Factors.

Auxins are one of the most important and studied phytohormones in nature. Auxin signaling and perception take place in the cytosol, where the auxin is sensed. Then, in the nucleus, the auxin response factors (ARF) promote the expression of early-response genes. It is well known that not all plants respond to the same amount and type of auxins and that the response can be very different even among plants of the same species, as we present here. Here we investigate the behavior of ARF in response to various auxins in Agave angustifolia Haw., A. fourcroydes Lem. and A. tequilana Weber var. Azul. By screening the available database of A. tequilana genes, we have identified 32 ARF genes with high sequence identity in the conserved domains, grouped into three main clades. A phylogenetic tree was inferred from alignments of the 32 Agave ARF protein sequences and the evolutionary relationship with other species was analyzed. AteqARF 4, 15, 21, and 29 were selected as a representative diverse sample coming from each of the different subclades that comprise the two main clades of the inferred phylogenetic reconstruction. These ARFs showed differential species-specific expression patterns in the presence of indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D). Interestingly, A. angustifolia showed different phenotypes in the presence and absence of auxins. In the absence of auxin, A. angustifolia produces roots, while shoots are developed in the presence of IAA. However, in the presence of 2,4-D, the plant meristem converts into callus. According to our results, it is likely that AteqARF15 participates in this outcome.

DNA Methylation and Transcriptomic Next-Generation Technologies in Cereal Genomics.

RNA sequencing (RNA-seq) coupled to DNA methylation strategies enables the detection and characterization of genes which expression levels might be mediated by DNA methylation. Here we describe a bioinformatics protocol to analyze gene expression levels using RNA-seq data that allow us to identify candidate genes to be tested by bisulfite assays. The candidate methylated genes are usually those that are low expressed in a particular condition or developmental stage.

Signaling Overview of Plant Somatic Embryogenesis.

Somatic embryogenesis (SE) is a means by which plants can regenerate bipolar structures from a somatic cell. During the process of cell differentiation, the explant responds to endogenous stimuli, which trigger the induction of a signaling response and, consequently, modify the gene program of the cell. SE is probably the most studied plant regeneration model, but to date it is the least understood due to the unclear mechanisms that occur at a cellular level. In this review, the authors seek to emphasize the importance of signaling on plant SE, highlighting the interactions between the different plant growth regulators (PGR), mainly auxins, cytokinins (CKs), ethylene and abscisic acid (ABA), during the induction of SE. The role of signaling is examined from the start of cell differentiation through the early steps on the embryogenic pathway, as well as its relation to a plant's tolerance of different types of stress. Furthermore, the role of genes encoded to transcription factors (TFs) during the embryogenic process such as the LEAFY COTYLEDON (LEC), WUSCHEL (WUS), BABY BOOM (BBM) and CLAVATA (CLV) genes, Arabinogalactan-proteins (AGPs), APETALA 2 (AP2) and epigenetic factors is discussed.

Detection of Histone Modifications Associated with miRNAs.

The posttranslational modifications of histones and miRNAs are key epigenetic mechanisms participating in the development, growth, and reproduction of plants. Recently, coordination between these two mechanisms has been demonstrated; each mechanism can be controlled by the other for the regulation of several biological processes. For example, the acetylation of histone H3, a key modification for chromatin remodeling and gene activation, has been linked to the actions of miRNA. In this work, we describe a method for the isolation and immunodetection of two posttranslational modifications in the residues of lysine 9 and 27 of H3, which have been associated with long miRNAs in plants.

5-Azacytidine: A Promoter of Epigenetic Changes in the Quest to Improve Plant Somatic Embryogenesis.

Somatic embryogenesis (SE) is a widely studied process due to its biotechnological potential to generate large quantities of plants in short time frames and from different sources of explants. The success of SE depends on many factors, such as the nature of the explant, the microenvironment generated by in vitro culture conditions, and the regulation of gene expression, among others. Epigenetics has recently been identified as an important factor influencing SE outcome. DNA methylation is one of the most studied epigenetic mechanisms due to its essential role in gene expression, and its participation in SE is crucial. DNA methylation levels can be modified through the use of drugs such as 5-Azacytidine (5-AzaC), an inhibitor of DNA methylation, which has been used during SE protocols. The balance between hypomethylation and hypermethylation seems to be the key to SE success. Here, we discuss the most prominent recent research on the role of 5-AzaC in the regulation of DNA methylation, highlighting its importance during the SE process. Also, the molecular implications that this inhibitor might have for the increase or decrease in the embryogenic potential of various explants are reviewed.

Chromatin Immunoprecipitation (ChiP) Protocol for the Analysis of Gene Regulation by Histone Modifications in Agave angustifolia Haw.

Chromatin is a dynamic entity that regulates different biological processes crucial for the proper functioning of the cell. Chromatin regulation depends largely on the interactions that occur between DNA with histones and nonhistone proteins. The chromatin immunoprecipitation assay (ChiP) is a widely used technique for the study of these DNA-histone and DNA-nonhistone interactions and their biological repercussions. Here we describe a ChiP protocol that allows in vivo analysis of the associations of histone modifications with genomic DNA in Agave angustifolia Haw. Although this protocol is established for A. angustifolia, it can be used in other species to obtain similar results. We also propose a strategy to shorten the times in some steps of the standard protocol.

Dad's Snoring May Have Left Molecular Scars in Your DNA: the Emerging Role of Epigenetics in Sleep Disorders.

The sleep-wake cycle is a biological phenomena under the orchestration of neurophysiological, neurochemical, neuroanatomical, and genetical mechanisms. Moreover, homeostatic and circadian processes participate in the regulation of sleep across the light-dark period. Further complexity of the understanding of the genesis of sleep engages disturbances which have been characterized and classified in a variety of sleep-wake cycle disorders. The most prominent sleep alterations include insomnia as well as excessive daytime sleepiness. On the other side, several human diseases have been linked with direct changes in DNA, such as chromatin configuration, genomic imprinting, DNA methylation, histone modifications (acetylation, methylation, ubiquitylation or sumoylation, etc.), and activating RNA molecules that are transcribed from DNA but not translated into proteins. Epigenetic theories primarily emphasize the interaction between the environment and gene expression. According to these approaches, the environment to which mammals are exposed has a significant role in determining the epigenetic modifications occurring in chromosomes that ultimately would influence not only development but also the descendants' physiology and behavior. Thus, what makes epigenetics intriguing is that, unlike genetic variation, modifications in DNA are altered directly by the environment and, in some cases, these epigenetic changes may be inherited by future generations. Thus, it is likely that epigenetic phenomena might contribute to the homeostatic and/or circadian control of sleep and, possibly, have an undescribed link with sleep disorders. An exciting new horizon of research is arising between sleep and epigenetics since it represents the relevance of the study of how the genome learns from its experiences and modulates behavior, including sleep.

Stem Cells from Dental Pulp: What Epigenetics Can Do with Your Tooth.

Adult stem cells have attracted scientific attention because they are able to self-renew and differentiate into several specialized cell types. In this context, human dental tissue-derived mesenchymal stem cells (hDT-MSCs) have emerged as a possible solution for repairing or regenerating damaged tissues. These cells can be isolated from primary teeth that are naturally replaced, third molars, or other dental tissues and exhibit self-renewal, a high proliferative rate and a great multilineage potential. However, the cellular and molecular mechanisms that determine lineage specification are still largely unknown. It is known that a change in cell fate requires the deletion of existing transcriptional programs, followed by the establishment of a new developmental program to give rise to a new cell lineage. Increasing evidence indicates that chromatin structure conformation can influence cell fate. In this way, reversible chemical modifications at the DNA or histone level, and combinations thereof can activate or inactivate cell-type-specific gene sequences, giving rise to an alternative cell fates. On the other hand, miRNAs are starting to emerge as a possible player in establishing particular somatic lineages. In this review, we discuss two new and promising research fields in medicine and biology, epigenetics and stem cells, by summarizing the properties of hDT-MSCs and highlighting the recent findings on epigenetic contributions to the regulation of cellular differentiation.

Assessment of molecular and epigenetic changes in the albinism of Agave angustifolia Haw.

Albinism in plants is a rare phenomenon that occurs in nature and is characterized by the total or partial loss of photosynthetic pigments. Although progress has been made in understanding the nature of this phenomenon, the precise causes and biological basis are still unexplored. Here, we study the genetic and epigenetic differences between green (G), variegated (V) and albino (A) A. angustifolia Haw. plantlets obtained by in vitro propagation in order to present new insights into albinism from a plant system that offers a unique set of biological phenotypic characteristics. Low transcript levels of genes involved in carotenoids and photosynthesis such as PSY, PDS, LCYƐ, rubS, PEPCase and LHCP suggest a disruption in these processes in albino plants. Due to a high level of genetic similarity being found between the three phenotypes, we analyzed global DNA methylation and different histone marks (H3K4me2, H3K36me2, H3K9ac, H3K9me2 and H3K27me3). Although no significant differences in global 5-methyl deoxicytidine were found, almost a 2-4.5-fold increase in H3K9ac was observed in albino plants in comparison with variegated or green plants, suggesting a change in chromatin compaction related to A. angustifolia albinism.

Plant hormone signaling in flowering: An epigenetic point of view.

Reproduction is one of the most important phases in an organism's lifecycle. In the case of angiosperm plants, flowering provides the major developmental transition from the vegetative to the reproductive stage, and requires genetic and epigenetic reprogramming to ensure the success of seed production. Flowering is regulated by a complex network of genes that integrate multiple environmental cues and endogenous signals so that flowering occurs at the right time; hormone regulation, signaling and homeostasis are very important in this process. Working alone or in combination, hormones are able to promote flowering by epigenetic regulation. Some plant hormones, such as gibberellins, jasmonic acid, abscisic acid and auxins, have important effects on chromatin compaction mediated by DNA methylation and histone posttranslational modifications, which hints at the role that epigenetic regulation may play in flowering through hormone action. miRNAs have been viewed as acting independently from DNA methylation and histone modification, ignoring their potential to interact with hormone signaling - including the signaling of auxins, gibberellins, ethylene, jasmonic acid, salicylic acid and others - to regulate flowering. Therefore, in this review we examine new findings about interactions between epigenetic mechanisms and key players in hormone signaling to coordinate flowering.