Characterization of DNA methyltransferase and demethylase genes in Fragaria vesca

Genome-Wide Analysis of DNA Demethylases in Land Plants and Their Expression Pattern in Rice

DNA demethylation is a very important biochemical pathway regulating a group of biological processes, such as embryo development, fruit ripening, and response to stress. Despite the essential role of DNA demethylases, their evolutionary relationship and detailed biological functions in different land plants remain unclear. In this study, 48 DNA demethylases in 12 land plants were identified and classified. A phylogenetic tree was constructed to demonstrate the evolutionary relationships among these DNA demethylases, indicating how they are related across different species. Conserved domain, protein motif, and gene structure analysis showed that these 48 DNA demethylases fell into the presently identified four classes of DNA demethylases. Amino acid alignment revealed conserved catalytic sites and a previously less-studied protein region (referred to as domain A) within the DNA demethylases. An analysis showed a conserved pattern of gene duplication for DNA demethylases throughout their evolutionary history, suggesting that these genes had been maintained due to their importance. The examination of promoter cis-elements displayed potential signaling and regulating pathways of DNA demethylases. Furthermore, the expression profile was analyzed to investigate the physiological role of rice DNA demethylase in different developmental stages, in tissues, and in response to stress and various phytohormone signals. The findings offer a deeper insight into the functional regions of DNA demethylases and their evolutionary relationships, which can guide future research directions. Understanding the role of DNA demethylases can lead to improved plant stress resistance and contribute to the development of better crop and fruit varieties.

Systematic Analysis of DNA Demethylase Gene Families in Foxtail Millet (Setaria italica L.) and Their Expression Variations after Abiotic Stresses

DNA methylation is a highly conserved epigenetic modification involved in many biological processes, including growth and development, stress response, and secondary metabolism. DNA demethylase (DNA-deMTase) genes have been identified in some plant species; however, there are no reports on the identification and analysis of DNA-deMTase genes in Foxtail millet (Setaria italica L.). In this study, seven DNA-deMTases were identified in S. italica. These DNA-deMTase genes were divided into four subfamilies (DML5, DML4, DML3, and ROS1) by phylogenetic and gene structure analysis. Further analysis shows that the physical and chemical properties of these DNA-deMTases proteins are similar, contain the typical conserved domains of ENCO3c and are located in the nucleus. Furthermore, multiple cis-acting elements were observed in DNA-deMTases, including light responsiveness, phytohormone responsiveness, stress responsiveness, and elements related to plant growth and development. The DNA-deMTase genes are expressed in all tissues detected with certain tissue specificity. Then, we investigated the abundance of DNA-deMTase transcripts under abiotic stresses (cold, drought, salt, ABA, and MeJA). The results showed that different genes of DNA-deMTases were involved in the regulation of different abiotic stresses. In total, our findings will provide a basis for the roles of DNA-deMTase in response to abiotic stress.

DNA methylation in the wild: epigenetic transgenerational inheritance can mediate adaptation in clones of wild strawberry (Fragaria vesca)

Due to the accelerating climate change, it is crucial to understand how plants adapt to rapid environmental changes. Such adaptation may be mediated by epigenetic mechanisms like DNA methylation, which could heritably alter phenotypes without changing the DNA sequence, especially across clonal generations. However, we are still missing robust evidence of the adaptive potential of DNA methylation in wild clonal populations. Here, we studied genetic, epigenetic and transcriptomic variation of Fragaria vesca, a predominantly clonally reproducing herb. We examined samples from 21 natural populations across three climatically distinct geographic regions, as well as clones of the same individuals grown in a common garden. We found that epigenetic variation was partly associated with climate of origin, particularly in non-CG contexts. Importantly, a large proportion of this variation was heritable across clonal generations. Additionally, a subset of these epigenetic changes affected the expression of genes mainly involved in plant growth and responses to pathogen and abiotic stress. These findings highlight the potential influence of epigenetic changes on phenotypic traits. Our findings indicate that variation in DNA methylation, which can be environmentally inducible and heritable, may enable clonal plant populations to adjust to their environmental conditions even in the absence of genetic adaptation.

Identification and gene expression analysis of cytosine-5 DNA methyltransferase and demethylase genes in Amaranthus cruentus L. under heavy metal stress

Amaranth has become increasingly popular due to its highly nutritious grains and ability to tolerate environmental stress. The mechanism underlying defense and adaptation to environmental stress is a complicated process involving DNA methylation and demethylation. These epigenetic features have been well documented to play an important role in plant stress response, including heavy metal-induced stress. This study was aimed at the identification and analysis of cytosine-5 DNA methyltransferase (C5-MTase) and demethylase (DMTase) genes in Amaranthus cruentus. Eight C5-MTase and two DMTase genes were identified and described in response to individual heavy metals (Cd, Pb, Zn, Mn) and their combination (Cd/Pb, Cd/Zn, Pb/Zn) in root and leaf tissues. Studied heavy metals, individually and in combinations, differentially regulated C5-MTase and DMTase gene expression. Interestingly, most of the genes were transcriptionally altered under Zn exposure. Our results suggest that identified amaranth MTase and DMTase genes are involved in heavy metal stress responses through regulating DNA methylation and demethylation level in amaranth plants.

Identification and Characterization of DNA Demethylase Genes and Their Association With Thermal Stress in Wheat (Triticum aestivum L.)

DNA demethylases (dMTases) are essential proteins in plants that regulate DNA methylation levels. The dMTase genes have been explored in a number of plant species, however, members of this family have not been reported in wheat. We identified 12 wheat dMTase genes divided into two subfamilies: repressor of silencing 1 (ROS1) and DEMETER-Like (DML). The TadMTases in the same subfamily or clade in the phylogenetic tree have similar gene structures, protein motifs, and domains. The promoter sequence contains multiple cis-regulatory elements (CREs) that respond to abiotic stress, hormones, and light, suggesting that the majority of TadMTase genes play a role in wheat growth, development, and stress response. The nuclear localization signals (NLSs), subcellular localization, and SRR motifs were also analyzed. The expression profile analyses revealed that TadMTase genes showed differential gene expression patterns in distinct developmental stages and tissues as well as under heat stress (HS). Furthermore, the qRT-PCR analysis revealed that TadMTase gene expression differed amongst wheat cultivars with varying degrees of HS tolerance. Overall, this work contributes to the understanding of the biological function of wheat dMTases and lays the foundation for future investigations.

Azacytidine arrests ripening in cultivated strawberry (Fragaria × ananassa) by repressing key genes and altering hormone contents

BACKGROUND

Strawberry ripening involves a number of irreversible biochemical reactions that cause sensory changes through accumulation of sugars, acids and other compounds responsible for fruit color and flavor. The process, which is strongly dependent on methylation marks in other fruits such as tomatoes and oranges, is highly controlled and coordinated in strawberry.

RESULTS

Repeated injections of the hypomethylating compound 5-azacytidine (AZA) into green and unripe Fragaria × ananassa receptacles fully arrested the ripening of the fruit. The process, however, was reversible since treated fruit parts reached full maturity within a few days after AZA treatment was stopped. Transcriptomic analyses showed that key genes responsible for the biosynthesis of anthocyanins, phenylpropanoids, and hormones such as abscisic acid (ABA) were affected by the AZA treatment. In fact, AZA downregulated genes associated with ABA biosynthetic genes but upregulated genes associated with its degradation. AZA treatment additionally downregulated a number of essential transcription factors associated with the regulation and control of ripening. Metabolic analyses revealed a marked imbalance in hormone levels, with treated parts accumulating auxins, gibberellins and ABA degradation products, as well as metabolites associated with unripe fruits.

CONCLUSIONS

AZA completely halted strawberry ripening by altering the hormone balance, and the expression of genes involves in hormone biosynthesis and degradation processes. These results contradict those previously obtained in other climacteric and fleshly fruits, where AZA led to premature ripening. In any case, our results suggests that the strawberry ripening process is governed by methylation marks.

ROS1 promotes low temperature-induced anthocyanin accumulation in apple by demethylating the promoter of anthocyanin-associated genes

Low temperature can affect the growth and development of plants through changes in DNA demethylation patterns. Another known effect of low temperature is the accumulation of anthocyanin pigments. However, it is not known whether the two phenomena are linked, specifically, whether DNA demethylation participates in anthocyanin accumulation in response to low-temperature stress. The ROS1 gene is involved in plant DNA demethylation and influences methylation levels in response to low temperature stress. In this study, using RNA sequencing, we detected that the transcription levels of MdROS1 correlate with the anthocyanin content, as well as with those of anthocyanin biosynthesis-related genes in apple (Malus domestica), at low temperatures. Genomic bisulfite sequencing showed that the methylation levels of the promoters of the anthocyanin related genes MdCHS, MdCHI, MdF3'H, MdANS, MdUFGT, and MdMYB10 decreased in apple leaves after low-temperature treatment. Similar expression and methylation results were also found in apple fruit. Transiently silencing MdROS1 in the leaves and fruit of apple cultivars inhibited the accumulation of anthocyanins and led to decreased expression of anthocyanin biosynthetic genes, and the opposite results were detected in MdROS1-overexpressing leaves and fruit. A promoter binding assay showed that the conserved RRD-DME domains of MdROS1 directly bind to the promoters of MdF3'H and MdUFGT. Taken together, these results suggest that ROS1 affects the anthocyanin biosynthetic pathway by decreasing the methylation level of anthocyanin-related gene promoters, thereby increasing their expression and increasing anthocyanin accumulation.

Exploration of the Potential Transcriptional Regulatory Mechanisms of DNA Methyltransferases and MBD Genes in Petunia Anther Development and Multi-Stress Responses

Cytosine-5 DNA methyltransferases (C5-MTases) and methyl-CpG-binding-domain (MBD) genes can be co-expressed. They directly control target gene expression by enhancing their DNA methylation levels in humans; however, the presence of this kind of cooperative relationship in plants has not been determined. A popular garden plant worldwide, petunia (Petunia hybrida) is also a model plant in molecular biology. In this study, 9 PhC5-MTase and 11 PhMBD proteins were identified in petunia, and they were categorized into four and six subgroups, respectively, on the basis of phylogenetic analyses. An expression correlation analysis was performed to explore the co-expression relationships between PhC5-MTases and PhMBDs using RNA-seq data, and 11 PhC5-MTase/PhMBD pairs preferentially expressed in anthers were identified as having the most significant correlations (Pearson’s correlation coefficients > 0.9). Remarkably, the stability levels of the PhC5-MTase and PhMBD pairs significantly decreased in different tissues and organs compared with that in anthers, and most of the selected PhC5-MTases and PhMBDs responded to the abiotic and hormonal stresses. However, highly correlated expression relationships between most pairs were not observed under different stress conditions, indicating that anther developmental processes are preferentially influenced by the co-expression of PhC5-MTases and PhMBDs. Interestingly, the nuclear localization genes PhDRM2 and PhMBD2 still had higher correlations under GA treatment conditions, implying that they play important roles in the GA-mediated development of petunia. Collectively, our study suggests a regulatory role for DNA methylation by C5-MTase and MBD genes in petunia anther maturation processes and multi-stress responses, and it provides a framework for the functional characterization of C5-MTases and MBDs in the future.

Genome-wide identification and analysis of DNA methyltransferase and demethylase gene families in Dendrobium officinale reveal their potential functions in polysaccharide accumulation

BACKGROUND

DNA methylation is a conserved and important epigenetic modification involved in the regulation of numerous biological processes, including plant development, secondary metabolism, and response to stresses. However, no information is available regarding the identification of cytosine-5 DNA methyltransferase (C5-MTase) and DNA demethylase (dMTase) genes in the orchid Dendrobium officinale.

RESULTS

In this study, we performed a genome-wide analysis of DoC5-MTase and DodMTase gene families in D. officinale. Integrated analysis of conserved motifs, gene structures and phylogenetic analysis showed that eight DoC5-MTases were divided into four subfamilies (DoCMT, DoDNMT, DoDRM, DoMET) while three DodMTases were divided into two subfamilies (DoDML3, DoROS1). Multiple cis-acting elements, especially stress-responsive and hormone-responsive ones, were found in the promoter region of DoC5-MTase and DodMTase genes. Furthermore, we investigated the expression profiles of DoC5-MTase and DodMTase in 10 different tissues, as well as their transcript abundance under abiotic stresses (cold and drought) and at the seedling stage, in protocorm-like bodies, shoots, and plantlets. Interestingly, most DoC5-MTases were downregulated whereas DodMTases were upregulated by cold stress. At the seedling stage, DoC5-MTase expression decreased as growth proceeded, but DodMTase expression increased.

CONCLUSIONS

These results provide a basis for elucidating the role of DoC5-MTase and DodMTase in secondary metabolite production and responses to abiotic stresses in D. officinale.

Dynamic Changes of DNA Methylation Induced by Heat Treatment Were Involved in Ethylene Signal Transmission and Delayed the Postharvest Ripening of Tomato Fruit

Deoxyribonucleic acid (DNA) methylation plays an important role in fruit ripening and senescence. Here, the role of DNA methylation of the CpG island of SlACS10, LeCTR1, LeEIN3, LeERT10, and SlERF-A1 genes induced by heat treatment (37 °C) in postharvest ripening of tomato fruit was studied. After heat treatment, the firmness and vitamin C content showed higher levels, the loss of aldehydes in volatile components was delayed, and the activities of methylase and demethylase decreased in tomato fruit. Moreover, in heat-treated fruit, significant changes in DNA methylation of SlACS10, LeCTR1, LeEIN3, LeERT10, and SlERF-A1 were induced, the expression of LeERT10 and LeEIN3 was inhibited, the expression of SlERF-A1 was increased, by which ethylene signal transmission might be suppressed and the postharvest ripening of tomato fruit was delayed. The present study provided valuable information for understanding the essential role of DNA methylation in the postharvest ripening of tomato fruit.

Characterization of DNA methylation variations during fruit development and ripening of Vitis vinifera (cv. 'Fujiminori')

The fruit is the most important economical organ in the grape; accordingly, to investigate the grapevine genomic methylation landscape and examine its functional significance during fruit development, we generated whole genome DNA methylation maps for various developmental stages in the fruit of grapevine. In this study, thirteen DNA methylation-related genes and their expression profiles were identified and analyzed. The methylation levels for mC, mCG, mCHG, and mCHH contexts in 65 days after flowering (65DAF) fruit (véraison stage) were higher than those in 40DAF (green stage) and 90DAF (mature stage) fruits. Relative to methylation in the mC context, methylation levels in the mCHH context were higher than those of mCG and mCHG. The DNA methylation level in the ncRNA regions was significantly higher than that in exon, gene, intron, and mRNA regions. The differentially methylated regions (DMRs) and differentially methylated promoters (DMPs) in 65DAF_vs_40DAF were both higher than those in 90DAF_vs_65DAF and 90DAF_vs_40DAF. Most DMRs (or DMPs) were involved in metabolic processes and cell processes, binding, and catalytic activity. These results indicated that DNA methylation represses gene expression during grape fruit development, and it broadens our understanding of the landscape and function of DNA methylation in grapevine genomes.

A roadmap for research in octoploid strawberry

The cultivated strawberry (Fragaria × ananassa) is an allo-octoploid species, originating nearly 300 years ago from wild progenitors from the Americas. Since that time the strawberry has become the most widely cultivated fruit crop in the world, universally appealing due to its sensory qualities and health benefits. The recent publication of the first high-quality chromosome-scale octoploid strawberry genome (cv. Camarosa) is enabling rapid advances in genetics, stimulating scientific debate and provoking new research questions. In this forward-looking review we propose avenues of research toward new biological insights and applications to agriculture. Among these are the origins of the genome, characterization of genetic variants, and big data approaches to breeding. Key areas of research in molecular biology will include the control of flowering, fruit development, fruit quality, and plant-pathogen interactions. In order to realize this potential as a global community, investments in genome resources must be continually augmented.

Genome-wide investigation and transcriptional analysis of cytosine-5 DNA methyltransferase and DNA demethylase gene families in tea plant (Camellia sinensis) under abiotic stress and withering processing

DNA methylation is a highly conserved epigenetic modification involved in many biological processes, including growth and development, stress response, and secondary metabolism. In the plant kingdom, cytosine-5 DNA methyltransferase (C5-MTase) and DNA demethylase (dMTase) genes have been identified in some plant species. However, to the best of our knowledge, no investigator has focused on the identification and analysis of C5-MTase and dMTase genes in tea plants (Camellia sinensis) based on genome-wide levels. In this study, eight CsC5-MTases and four dMTases were identified in tea plants. These CsC5-MTase genes were divided into four subfamilies, including CsMET, CsCMT, CsDRM and CsDNMT2. The CsdMTase genes can be classified into CsROS, CsDME and CsDML. Based on conserved domain analysis of these genes, the gene loss and duplication events occurred during the evolution of CsC5-MTase and CsdMTase. Furthermore, multiple cis-acting elements were observed in the CsC5-MTase and CsdMTase, including light responsiveness, phytohormone responsiveness, stress responsiveness, and plant growth and development-related elements. Then, we investigated the transcript abundance of CsC5-MTase and CsdMTase under abiotic stress (cold and drought) and withering processing (white tea and oolong tea). Notably, most CsC5-MTases, except for CsCMT1 and CsCMT2, were significantly downregulated under abiotic stress, while the transcript abundance of all four CsdMTase genes was significantly induced. Similarly, the same transcript abundance of CsC5-MTase and CsdMTase was found during withering processing of white tea and oolong tea, respectively. In total, our findings will provide a basis for the roles of CsC5-MTase and CsdMTase in response to abiotic stress and the potential functions of these two gene families in affecting tea flavor during tea withering processing.

N 6-Methyladenine DNA Modification in the Woodland Strawberry (Fragaria vesca) Genome Reveals a Positive Relationship With Gene Transcription

N 6-methyladenine (6mA) DNA modification has been detected in several eukaryotic organisms, where it plays important roles in gene regulation and epigenetic memory maintenance. However, the genome-wide distribution patterns and potential functions of 6mA DNA modification in woodland strawberry (Fragaria vesca) remain largely unknown. Here, we examined the 6mA landscape in the F. vesca genome by adopting single-molecule real-time sequencing technology and found that 6mA modification sites were broadly distributed across the woodland strawberry genome. The pattern of 6mA distribution in the long non-coding RNA was significantly different from that in protein-coding genes. The 6mA modification influenced the gene transcription and was positively associated with gene expression, which was validated by computational and experimental analyses. Our study provides new insights into the DNA methylation in F. vesca.

Transcriptome profiling of 'Kyoho' grape at different stages of berry development following 5-azaC treatment

Background

5-Azacytidine (5-azaC) promotes the development of ‘Kyoho’ grape berry but the associated changes in gene expression have not been reported. In this study, we performed transcriptome analysis of grape berry at five developmental stages after 5-azaC treatment to elucidate the gene expression networks controlling berry ripening.

Results

The expression patterns of most genes across the time series were similar between the 5-azaC treatment and control groups. The number of differentially expressed genes (DEGs) at a given developmental stage ranged from 9 (A3_C3) to 690 (A5_C5). The results indicated that 5-azaC treatment had not very great influences on the expressions of most genes. Functional annotation of the DEGs revealed that they were mainly related to fruit softening, photosynthesis, protein phosphorylation, and heat stress. Eight modules showed high correlation with specific developmental stages and hub genes such as PEROXIDASE 4, CAFFEIC ACID 3-O-METHYLTRANSFERASE 1, and HISTONE-LYSINE N-METHYLTRANSFERASE EZA1 were identified by weighted gene correlation network analysis.

Conclusions

5-AzaC treatment alters the transcriptional profile of grape berry at different stages of development, which may involve changes in DNA methylation.

Identification of DNA methyltransferases and demethylases in Solanum melongena L., and their transcription dynamics during fruit development and after salt and drought stresses

DNA methylation through the activity of cytosine-5-methyltransferases (C5-MTases) and DNA demethylases plays important roles in genome protection as well as in regulating gene expression during plant development and plant response to environmental stresses. In this study, we report on a genome-wide identification of six C5-MTases (SmelMET1, SmelCMT2, SmelCMT3a, SmelCMT3b, SmelDRM2, SmelDRM3) and five demethylases (SmelDemethylase_1, SmelDemethylase_2, SmelDemethylase_3, SmelDemethylase_4, SmelDemethylase_5) in eggplant. Gene structural characteristics, chromosomal localization and phylogenetic analyses are also described. The transcript profiling of both C5-MTases and demethylases was assessed at three stages of fruit development in three eggplant commercial F1 hybrids: i.e. 'Clara', 'Nite Lady' and 'Bella Roma', representative of the eggplant berry phenotypic variation. The trend of activation of C5-MTases and demethylase genes varied in function of the stage of fruit development and was genotype dependent. The transcription pattern of C5MTAses and demethylases was also assessed in leaves of the F1 hybrid 'Nite Lady' subjected to salt and drought stresses. A marked up-regulation and down-regulation of some C5-MTases and demethylases was detected, while others did not vary in their expression profile. Our results suggest a role for both C5-MTases and demethylases during fruit development, as well as in response to abiotic stresses in eggplant, and provide a starting framework for supporting future epigenetic studies in the species.

Characterization and Expression Analysis of ERF Genes in Fragaria vesca Suggest Different Divergences of Tandem ERF Duplicates

Ethylene-responsive factors (ERFs) play important roles in plant growth and development and in responses to abiotic stresses. However, little information was available about the ERF genes in woodland strawberry (Fragaria vesca), a genetic model plant for the Fragaria genus and Rosaceae family. In this study, 91 FveERF genes were identified, including 35 arrayed in tandem, indicating that tandem duplication is a major mechanism for the expansion of the FveERF family. According to their phylogenetic relationships with AtERFs from Arabidopsis thaliana, the tandem FveERF genes could be grouped into ancestral and lineage-specific tandem ones. The ancestral tandem FveERFs are likely derived from tandem duplications that occurred in the common ancestor of F. vesca and A. thaliana, whereas the lineage-specific ones are specifically present in the F. vesca lineage. The lineage-specific tandem FveERF duplicates are more conserved than the ancestral ones in sequence and structure. However, their expression in flowers and fruits is similarly diversified, indicating that tandem FveERFs have diverged rapidly after duplication in this respect. The lineage-specific tandem FveERFs display the same response patterns with only one exception under drought or cold, whereas the ancestral tandem ones are largely differentially expressed, suggesting that divergence of tandem FveERF expression under stress may have occurred later in the reproductive development. Our results provide evidence that the retention of tandem FveERF duplicates soon after their duplication may be related to their divergence in the regulation of reproductive development. In contrast, their further divergence in expression pattern likely contributes to plant response to abiotic stress.

Identification and expression analysis of strigolactone biosynthetic and signaling genes reveal strigolactones are involved in fruit development of the woodland strawberry (Fragaria vesca)

BACKGROUND

The development and ripening of fresh fruits is an important trait for agricultural production and fundamental research. Almost all plant hormones participate in this process. Strigolactones (SLs) are a new class of plant hormones that regulate plant organ development and stress tolerance, but little is known about their roles in fruit development.

RESULTS

In this study, we identified SL biosynthetic and signaling genes in woodland strawberry, a typical non-climacteric fruit, and analyzed the expression patterns of these genes in different plant tissues and developing fruits. One D27, two MAX1, and one LBO gene were identified as involved in SL biosynthesis, and one D14, one D3, and two D53 genes as related to SL signaling. The proteins encoded by these genes had similar motifs as SL biosynthetic and signaling proteins in rice and Arabidopsis. The genes had different expression levels in the root, stem, leaf, and petiole of woodland strawberry. In addition, the expression of most SL biosynthetic genes was high in developing carpel, anther, and style, while that of SL signaling genes was high in carpel and style, but low in anther, suggesting active SL biosynthesis and signaling in the developing carpel and style. Notably, the expression of SL biosynthetic and signaling genes was significantly increased in the receptacle after pollination and decreased during receptacle development. Moreover, low or no expression of these genes was detected in ripening fruits.

CONCLUSIONS

Our results suggest that SLs play a role in the early stages of woodland strawberry fruit development. Our findings provide insight into the function of SLs and will facilitate further study of the regulation by SLs of fresh fruit development.

MDR: an integrative DNA N6-methyladenine and N4-methylcytosine modification database for Rosaceae

Eukaryotic DNA methylation has been receiving increasing attention for its crucial epigenetic regulatory function. The recently developed single-molecule real-time (SMRT) sequencing technology provides an efficient way to detect DNA N6-methyladenine (6mA) and N4-methylcytosine (4mC) modifications at a single-nucleotide resolution. The family Rosaceae contains horticultural plants with a wide range of economic importance. However, little is currently known regarding the genome-wide distribution patterns and functions of 6mA and 4mC modifications in the Rosaceae. In this study, we present an integrated DNA 6mA and 4mC modification database for the Rosaceae (MDR, http://mdr.xieslab.org). MDR, the first repository for displaying and storing DNA 6mA and 4mC methylomes from SMRT sequencing data sets for Rosaceae, includes meta and statistical information, methylation densities, Gene Ontology enrichment analyses, and genome search and browse for methylated sites in NCBI. MDR provides important information regarding DNA 6mA and 4mC methylation and may help users better understand epigenetic modifications in the family Rosaceae.

The C2 protein of tomato leaf curl Taiwan virus is a pathogenicity determinant that interferes with expression of host genes encoding chromomethylases

Tomato (Solanum lycopersicum) is one of the most important crops worldwide and is severely affected by geminiviruses. Tomato leaf curl Taiwan virus (ToLCTWV), belonging to the geminiviruses, was isolated in Taiwan and causes tremendous crop loss. The geminivirus-encoded C2 proteins are crucial for a successful interaction between the virus and host plants. However, the exact functions of the viral C2 protein of ToLCTWV have not been investigated. We analyzed the molecular function(s) of the C2 protein by transient or stable expression in tomato cv. Micro-Tom and Nicotiana benthamiana. Severe stunting of tomato and N. benthamiana plants infected with ToLCTWV was observed. Expression of ToLCTWV C2-green fluorescent protein (GFP) fusion protein was predominately located in the nucleus and contributed to activation of a coat protein promoter. Notably, the C2-GFP fluorescence was distributed in nuclear aggregates. Tomato and N. benthamiana plants inoculated with potato virus X (PVX)-C2 displayed chlorotic lesions and stunted growth. PVX-C2 elicited hypersensitive responses accompanied by production of reactive oxygen species in N. benthamiana plants, which suggests that the viral C2 was a potential recognition target to induce host-defense responses. In tomato and N. benthamiana, ToLCTWV C2 was found to interfere with expression of genes encoding chromomethylases. N. benthamiana plants with suppressed NbCMT3-2 expression were more susceptible to ToLCTWV infection. Transgenic N. benthamiana plants expressing the C2 protein showed decreased expression of the NbCMT3-2 gene and pNbCMT3-2::GUS (β-glucuronidase) promoter activity. C2 protein is an important pathogenicity determinant of ToLCTWV and interferes with host components involved in DNA methylation.

Bioinformatic and expression analyses on carotenoid dioxygenase genes in fruit development and abiotic stress responses in Fragaria vesca

Carotenoid dioxygenases, including 9-cis-epoxycarotenoid dioxygenases (NCEDs) and carotenoid cleavage dioxygenases (CCDs), can selectively cleave carotenoids into various apocarotenoid products that play important roles in fleshy fruit development and abiotic stress response. In this study, we identified 12 carotenoid dioxygenase genes in diploid strawberry Fragaria vesca, and explored their evolution with orthologous genes from nine other species. Phylogenetic analyses suggested that the NCED and CCDL groups moderately expanded during their evolution, whereas gene numbers of the CCD1, CCD4, CCD7, and CCD8 groups maintained conserved. We characterized the expression profiles of FveNCED and FveCCD genes during flower and fruit development, and in response to several abiotic stresses. FveNCED1 expression positively responded to osmotic, cold, and heat stresses, whereas FveNCED2 was only induced under cold stress. In contrast, FveNCED2 was the unique gene highly and continuously increasing in receptacle during fruit ripening, which co-occurred with the increase in endogenous abscisic acid (ABA) content previously reported in octoploid strawberry. The differential expression patterns suggested that FveNCED1 and FveNCED2 were key genes for ABA biosynthesis in abiotic stress responses and fruit ripening, respectively. FveCCD1 exhibited the highest expression in most stages of flower and fruit development, while the other FveCCDs were expressed in a subset of stages and tissues. Our study suggests distinct functions of FveNCED and FveCCD genes in fruit development and stress responses and lays a foundation for future study to understand the roles of these genes and their metabolites, including ABA and other apocarotenoid products, in the growth and development of strawberry.

Rosaceae Fruit Development, Ripening and Post-harvest: An Epigenetic Perspective

Rosaceae is a family with an extraordinary spectrum of fruit types, including fleshy peach, apple, and strawberry that provide unique contributions to a healthy diet for consumers, and represent an excellent model for studying fruit patterning and development. In recent years, many efforts have been made to unravel regulatory mechanism underlying the hormonal, transcriptomic, proteomic and metabolomic changes occurring during Rosaceae fruit development. More recently, several studies on fleshy (tomato) and dry (Arabidopsis) fruit model have contributed to a better understanding of epigenetic mechanisms underlying important heritable crop traits, such as ripening and stress response. In this context and summing up the results obtained so far, this review aims to collect the available information on epigenetic mechanisms that may provide an additional level in gene transcription regulation, thus influencing and driving the entire Rosaceae fruit developmental process. The whole body of information suggests that Rosaceae fruit could become also a model for studying the epigenetic basis of economically important phenotypes, allowing for their more efficient exploitation in plant breeding.