Differences in the methylation patterns of the VaSTS1 and VaSTS10 genes of Vitis amurensis Rupr.

Resveratrol is a plant-derived phenol but the mechanism that regulates its biosynthesis remains unidentified. Stilbene synthase (STS) catalyzes resveratrol formation in vivo and we have proposed that inducers of resveratrol production affect STS expression through an unidentified epigenetic mechanism. To investigate the role of DNA methylation in resveratrol biosynthesis, we treated both rolB transgenic and empty vector control Vitis amurensis cell cultures with the DNA demethylation agent, 5-azacytidine. Treated cells had increased resveratrol production through activation of VaSTS10 expression. The lowest levels of cytosine methylation were at the 5′- and 3′-ends of the VaSTS1 protein-coding sequence. Cytosine methylation decreased mostly at the 5′- and 3′-ends of VaSTS10 after azaC treatment with an intriguing regularity in the number of cytosine nucleotides within the 5′- and 3′- ends of the protein-coding sequences. Thus, cytosine methylation is crucial for the regulation of the resveratrol biosynthetic pathway.     

Resveratrol content and expression patterns of stilbene synthase genes in <Emphasis Type="Italic">Vitis amurensis</Emphasis> cells treated with 5-azacytidine

DNA methylation is known to be involved in the regulation of plant development and defense mechanisms. However, there is a general lack of data on the role of methylation in plant secondary metabolism. We have investigated the effect of a cytidine analog, 5-azacytidine (azaC), which is known to block DNA methylation, on resveratrol biosynthesis and stilbene synthase (STS) gene expression in Vitis amurensis cultured cells. Resveratrol is a naturally occurring polyphenol that has been reported to exhibit a wide range of important biological and pharmacological properties. We previously obtained a control cell line of V. amurensis (VV) as well as a rolB-transgenic cell line of V. amurensis (VB2) that has a higher level of resveratrol accumulation. In our experimental setup, the azaC-treated VV and VB2 calli produced 0.092% and 0.455% dry weight (DW) resveratrol, respectively. We found that treatment with 200 μM of azaC resulted in 1.9- and 2.0-fold increases in resveratrol production in VV and VB2 calli, respectively. A quantitative real-time PCR assay for STS gene expression in the azaC-treated VV and VB2 cells revealed that there were statistically increased expression levels of VaSTS10 in VV calli and of VaSTS5, VaSTS6, and VaSTS10 in VB2 calli. These results demonstrate that azaC is able to increase resveratrol production in V. amurensis calli through a mechanism that involves the induction of STS gene expression.     

Effects of 5-azacytidine induced DNA demethylation on methyltransferase gene expression and resveratrol production in cell cultures of Vitis amurensis

DNA becomes methylated in vivo through the action of a specific group of enzymes known as methyltransferases or methylases. Plants are known to possess the methyltransferases (Met), chromo methyltransferases (CMT), and domainrearranged methyltransferases (DRM) methylase families, which affect cytosine methylation within different contexts. DNA methylation has been proposed to play a role in secondary plant metabolism, but there is a lack of valid data connecting these two processes. In this study, we treated control and transformed with rolB gene from Agrobacterium rhizogenes cell cultures of Vitis amurensis with the demethylation agent 5-azacytidine (azaC). The purpose of the current investigation was to study effects of induced DNA demethylation on methyltransferase gene expression in connection to resveratrol production, a naturally occurring polyphenol that has a wide range of intriguing biological properties. Using semi-quantitative and real-time PCR, we showed that rolB gene transformation of V. amurensis cells decreased Met and CMT expression, but significantly increased DRM expression. AzaC treatment of the control and the rolB-transgenic calli significantly increased expression of all methylases (excluding Met). Following 3 months of azaC treatment, we detected significantly elevated levels of rolB gene expression in the transgenic calli. In current paper, we discuss how methylase expression may influence resveratrol biosynthesis and rolB transgene expression. Effects of azaC application are discussed.     

Resveratrol content and expression of phenylalanine ammonia-lyase and stilbene synthase genes in rolC transgenic cell cultures of Vitis amurensis

Resveratrol, a naturally occurring polyphenol, has been reported to exhibit a wide range of valuable biological and pharmacological properties. In the present investigation, we show that transformation of Vitis amurensis Rupr. with the oncogene rolC of Agrobacterium rhizogenes increased resveratrol production in the two transformed callus cultures 3.7 and 11.9 times. The rolC-transformed calli were capable of producing 0.099% and 0.144% dry weight of resveratrol. We characterized phenylalanine ammonia-lyase (PAL) and stilbene synthase (STS) gene expression in the two rolC transgenic callus cultures of V. amurensis. In the rolC transgenic culture with higher resveratrol content, expression of VaPAL3, VaSTS3, VaSTS4, VaSTS5, VaSTS6, VaSTS8, VaSTS9, and VaSTS10 was increased; while in the rolC culture with lower resveratrol content, expression of VaPAL3 and VaSTS9 was increased. We suggest that transformation of V. amurensis calli with the rolС gene induced resveratrol accumulation via selective enhancement of expression of individual PAL and STS genes involved in resveratrol biosynthesis. We compared the data on PAL and STS gene expression in rolC transgenic calli with the previously obtained results for rolB transgenic calli of V. amurensis. We propose that the transformation of V. amurensis with the rolC and rolB genes of A. rhizogenes increased resveratrol accumulation through different regulatory pathways.     

Influence of calcium influx induced by the calcium ionophore, A23187, on resveratrol content and the expression of CDPK and STS genes in the cell cultures of Vitis amurensis

The present study examines the effect of calcium influx induced by the calcium ionophore (CI) on the biosynthesis of resveratrol and the expression of stilbene synthase (STS) and calcium-dependent protein kinase (CDPK) genes in cell cultures of Vitis amurensis, which have different levels of resveratrol production. The present study utilized the control cell culture V2 of V. amurensis, which contains no more than 0.02?% dry weight (DW) of resveratrol, in addition to rolB transgenic cell cultures VB1 and VB2, which have increased resveratrol contents (0.1–0.8?% DW). Treatment with the CI at a 1?μM concentration significantly increased STS gene expression (6 of 10 analyzed STS genes) and resveratrol production in the control V2 cell culture by fourfold; however, use of the CI at 10?μM significantly decreased resveratrol production by 2–4 fold in all cell cultures tested. In the control V2 grape cell culture, treatment with the CI increased expression of all of the CDPK genes except VaCDPK1a and VaCDPK3a. In the rolB transgenic VB2 grape cell culture treated with the CI, we detected alterations in expression of several CDPK genes, but these changes in gene expression were not significant. Our results indicated that treatment with 1?μM of the CI increased resveratrol content and production in control grape cells by selectively increasing the expression of STS genes. Conversely, the CI treatment did not significantly increase resveratrol content and production, or the expression of CDPK or STS genes in the rolB transgenic cells. Likely, untreated VB2 cells have increased concentrations of cytoplasmic calcium, and therefore, treatment with the CI did not significantly change CDPK expression. These results suggest that the rolB gene has an important role in the regulation of calcium-dependent transduction pathways in transformed cells.     

Effect of long-term cultivation on resveratrol accumulation in a high-producing cell culture of Vitis amurensis

Resveratrol is a polyphenol, present in grapes, peanuts, and other plant sources, with a wide range of valuable biological activities. We established a Vitis amurensis cell culture accumulating high levels of resveratrol by introducing the rolB gene of Agrobacterium rhizogenes in the V. amurensis genome, and studied the stability of resveratrol accumulation during 27 months of continuous subculturing. This study demonstrates a decline in the high level of resveratrol production by the rolB transgenic cell line during its long-term cultivation. Elicitation of the rolB transgenic calli with methyl jasmonate and salicylic acid, which are known to stimulate the production of plant secondary metabolites, resulted in a recovery of resveratrol accumulation in the rolB transgenic cell culture, while the empty vector-transformed culture with trace starting content of resveratrol exhibited low inducibility to the treatment.     

Chromosome variability in grape (Vitis amurensis Rupr.) cells transformed with plant Oncogene rolB

The numbers of chromosomes and nucleoli in cultured cells of Vitis amurensis transformed with the rolB oncogene from A. rhizogenes have been studied. In general, the integration of the rolB gene in grape DNA mostly caused the elevation of the level of the chromosome variability, as well as higher numbers of nucleoli in the cultured cells. The possible influence of the observed chromosomal modifications on the productivity parameters of the grape cell cultures is discussed.     

Unstable expression of transgene is associated with the methylation of CAG promoter in the offspring from the same litter of homozygous transgenic mice

Transgenic animals have been established for studying gene function, improving animals’ production traits, and providing organ models for the exploration of human diseases. However, the stability of inheritance and transgene expression in transgenic animals has gained extensive attention. The unstable expression of transgene through DNA methyltransferase (DNMT) targeting to the methylation of transgenic DNA such as CAG promoter and Egfp coding region in homozygous transgenic animals is still unknown. In the present study, the offspring from the same litter of homozygous transgenic mice carrying ubiquitously expressed enhanced green fluorescence protein driven by CMV early enhancer/chicken β-actin (CAG) promoter was observed to have unstable expression of transgene Egfp, quantitative PCR, western blot and bisulfite sequencing were conducted to quantify the expressional characteristics and methylation levels in various tissues. The correlation between transgene expression and methylation was analyzed. We have found that transgene expression is dependent on the methylation of CAG promoter, but not Egfp coding region. We have also characterized the correlation between the methylation of CAG promoter and DNMT, and found that only Dnmt3b expression is correlated with the methylation of CAG promoter. In conclusion, Dnmt3b-related methylation of CAG promoter can inhibit the transgene expression and may result in the unstable expression of transgene in the offspring from the same litter of homozygous transgenic mice.     

The influence of the rolC gene on isoflavonoid production in callus cultures of Maackia amurensis

The polyphenolic complex of Maackia amurensis, as well as a complex of isoflavonoids from M. amurensis callus cultures, display strong hepatoprotective effects in experimental animal and human studies. To increase the yield of polyphenols in cultures of M. amurensis, calli were transformed with the rolC gene as well as with an empty vector that was used as a control. HPLC analysis revealed that the transgenic cultures produced the same complex of isoflavonoids. The complex consisted of 20 compounds, including isoflavones and their glucosides as well as pterocarpans and their glucosides. The cultures transformed with either the empty vector or the rolC gene construct produced on average 1.22 % dry weight (DW) and 1.39 % DW of isoflavonoids, respectively. Isoflavonoid production in the transformed callus lines carrying the empty vector and the rolC gene construct reached 106 and 146 mg/L, respectively. Moreover, the rolC gene construct promoted cell growth and overall cell productivity. The transgenic callus lines expressing the rolC gene exhibited higher levels of the following six isoflavonoids: daidzein, calycosin, formononetin, 4′-Ο-β-glucopyranosyldaidzin, maackiain and 6′-O-malonyl-3-O-β-D-glucopyranosylmaackiain. However, lower levels of genistin were observed in rolC calli than in those carrying the empty vector.     

Locus- and Site-Specific DNA Methylation of 19 kDa Zein Genes in Maize

An interesting question in maize development is why only a single zein gene is highly expressed in each of the 19-kDa zein gene clusters (A and B types), z1A2-1 and z1B4, in the immature endosperm. For instance, epigenetic marks could provide a structural difference. Therefore, we investigated the DNA methylation of the arrays of gene copies in both promoter and gene body regions of leaf (non-expressing tissue as a control), normal endosperm, and cultured endosperm. Although we could show that expressed genes have much lower methylation levels in promoter regions than silent ones in both leaf and normal endosperm, there was surprisingly also a difference in the pattern of the z1A and z1B gene clusters. The expression of z1B gene is suppressed by increased DNA methylation and activated with reduced DNA methylation, whereas z1A gene expression is not. DNA methylation in gene coding regions is higher in leaf than in endosperm, whereas no significant difference is observed in gene bodies between expressed and non-expressed gene copies. A median CHG methylation (25–30%) appears to be optimal for gene expression. Moreover, tissue-cultured endosperm can reset the DNA methylation pattern and tissue-specific gene expression. These results reveal that DNA methylation changes of the 19-kDa zein genes is subject to plant development and tissue culture treatment, but varies in different chromosomal locations, indicating that DNA methylation changes do not apply to gene expression in a uniform fashion. Because tissue culture is used to produce transgenic plants, these studies provide new insights into variation of gene expression of integrated sequences.     

Activation of stilbene synthesis in cell cultures of <Emphasis Type="Italic">Vitis amurensis</Emphasis> by calcium-dependent protein kinases <Emphasis Type="Italic">VaCPK1</Emphasis> and <Emphasis Type="Italic">VaCPK26</Emphasis>

Stilbenes, including trans-resveratrol (3,4′,5-trihydroxy-trans-stilbene), are known to exert beneficial health effects and contribute to plant biotic stress resistance. Much remains to be discovered about the cell signaling pathways regulating stilbene biosynthesis. It has recently been shown that overexpression of the calcium-dependent protein kinase VaCPK20 gene considerably increased t-resveratrol accumulation in cell cultures of Vitis amurensis. In this study, we analyzed the involvement of other CDPK family members, VaCPK1 and VaCPK26, on stilbene synthesis and biomass production by cell cultures of V. amurensis. We showed that overexpression of the VaCPK1 and 26 genes induced production of stilbenes by 1.7–4.6-fold (for VaCPK1) and by 2.5–6.2-fold (for VaCPK26) in several independently established cell lines compared to the empty vector-transformed control. Using HPLC-UV-MS, we detected five stilbenes in the grape cells: t-resveratrol diglucoside, t-piceid, t-resveratrol, ε- and δ-viniferin. The VaCPK1- and VaCPK26-transformed calli were capable of producing 1.4–3.1 and 1.8–4.9 mg/l of t-resveratrol, respectively (up to 0.4 for and 0.6 mg/g of dry weight for VaCPK26 and VaCPK1, respectively), while the control line synthesized only 0.5 mg/l of t-resveratrol (0.07 mg/g DW). The up-regulation of t-resveratrol production in the VaCPK1- and VaCPK26-overexpressing grape calli correlated with a significant up-regulation of stilbene synthase (STS) gene expression, especially VaSTS7. The data indicate that VaCPK1 and 26 genes, which are close homologues of VaCPK20, are positive regulators of stilbene biosynthesis in grapevine.     

Effect of the rol genes from Agrobacterium Rhizogenes on the content and structure of pectic substances and glycanase activity in Rubia Cordifolia transgenic cell cultures

The expression of the rolB gene was found to increase the pectic yield in Rubia cordifolia cells, while the rolC gene inhibited the pectin production, which correlated with its expression level. The expression of the rolA, rolB, and rolC genes led to an increase in the content of arabinogalactan (AG) in cells. The increase in the expression of the rolB and rolC genes resulted in a more significant reduction in the content of arabinose residues in pectin, which was accompanied by an increased activity of α-L-arabinofuranosidase in cells. Moreover, the amount of galactose residues in pectin increased with the enhancement of the rolB expression due to a decrease in the activity of β-galactosidase in cells. The content of galacturonic acid residues in pectin from transgenic cultures decreased in the following order: rolC > rolB > rolA. The amount of arabinose residues in AG decreased independently of the gene type. The amount of arabinose residues in AG was found to be considerably reduced when the rolB expression level was increased.     

Resistance to ACNU induced toxicity in transgenic tobacco suspension cultures withada gene transferred fromEscherichia coli

The protein coding region of theE. coli DNA repair geneada combined with the CaMV 35S promoter has been transferred to tobacco by means ofAgrobacterium tumefaciens Ti plasmid. In transgenic plants having theada gene in a sense orientation, detectable amounts of O⁶-alkylguanine-DNA-alkyltransferase has been found whereas in non-transformed plants this activity is absent. Cell suspension cultures derived from the former plants showed lower sensitivity to the toxic (growth inhibiting) effects of the bifunctional alkylating agent 1-(2-chloroethyl)-1-nitroso-3-(aminomethyl-1,3-diazinylo)-methylurea compared with cell cultures derived from a control non-transformed plant or from transgenic plants harbouring theada gene in an opposite, non-sense orientation.     

Effects of the Calmodulin Antagonist W7 on Resveratrol Biosynthesis in Vitis amurensis Rupr.

The calmodulin antagonist N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide (W7) binds to calmodulzin and inhibits Ca²⁺/calmodulin-regulated enzyme activities. In plant cells, W7 inhibits the activity of calcium-dependent protein kinases (CDPKs)—the major calcium sensors in plants. In the present study, we examined the effect of W7 on increased resveratrol biosynthesis and expression of CDPK and stilbene synthase (STS) genes in a cell culture of Vitis amurensis Rupr. We used coumaric acid (CA), salicylic acid (SA), and phenylalanine (Phe) to increase the content of resveratrol in V. amurensis calli, since its content is low under standard conditions. W7 significantly decreased resveratrol production and expression of STS genes in CA-, SA-, and Phe-treated grape cells. Also, treatment of the V. amurensis calli with SA, Phe, or CA considerably increased expression of VaCDPK1a (with SA, Phe), VaCDPK1L (with SA, Phe), VaCDPK2a (with Phe) genes, and decreased expression of VaCDPK3a (with CA). Addition of W7 to CA-, SA-, and Phe-treated grape cells reversed this effect, resulting in increased VaCDPK3a expression and decreased VaCDPK1a, VaCDPK1L, and VaCDPK2a expression. The results obtained suggest that CDPK activities might play an important role in resveratrol biosynthesis.