[Show abstract][Hide abstract] ABSTRACT: Lignin biosynthesis and its transcriptional regulatory networks have been studied in model plants and woody trees. However, lignification also occurs in some fleshy fruit and has rarely been considered in this way. Loquat (Eriobotrya japonica) is one such convenient tissue for exploring the transcription factors involved in regulating fruit flesh lignification. Firmness and lignin content of 'Luoyangqing' loquat were fund to increase during low-temperature storage as a typical symptom of chilling injury, while heat treatment (HT) and low-temperature conditioning (LTC) effectively alleviated them. Two novel EjMYB genes, EjMYB1 and EjMYB2, were isolated and were found to be localized in the nucleus. These genes responded differently to low temperature, with EjMYB1 induced and EjMYB2 inhibited at 0 °C. They also showed different temperature responses under HT and LTC conditions, and may be responsible for different regulation of flesh lignification at the transcriptional level. Transactivation assays indicated that EjMYB1 and EjMYB2 are a transcriptional activator and repressor, respectively. EjMYB1 activated promoters of both Arabidopsis and loquat lignin biosynthesis genes, while EjMYB2 countered the inductive effects of EjMYB1. This finding was also supported by transient overexpression in tobacco. Regulation of lignification by EjMYB1 and EjMYB2 is likely to be achieved via their competitive interaction with AC elements in the promoter region of lignin biosynthesis genes such as Ej4CL1.
Journal of Experimental Botany 05/2014; · 5.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The AP2/ERF gene family encodes plant-specific transcription factors. In model plants, AP2/ERF genes have been shown to be expressed in response to developmental and environmental stimuli, and many function downstream of the ethylene, biotic, and abiotic stress signaling pathways. In citrus, ethylene is effective in regulation citrus fruit quality, such as degreening and aroma. However, information about the citrus AP2/ERF family is limited, and would enhance our understanding of fruit responses to environmental stress, fruit development and quality. CitAP2/ERF genes were isolated using the citrus genome database, and their expression patterns analyzed by real-time PCR using various orange organs and samples from a fruit developmental series. 126 sequences with homologies to AP2/ERF proteins were identified from the citrus genome, and, on the basis of their structure and sequence, assigned to the ERF family (102), AP2 family (18), RAV family (4) and Soloist (2). MEME motif analysis predicted the defining AP2/ERF domain and EAR repressor domains. Analysis of transcript accumulation in Citrus sinensis cv. 'Newhall' indicated that CitAP2/ERF genes show organ-specific and temporal expression, and provided a framework for understanding the transcriptional regulatory roles of AP2/ERF gene family members in citrus. Hierarchical cluster analysis and t tests identified regulators that potentially function during orange fruit growth and development.
[Show abstract][Hide abstract] ABSTRACT: Bagging is a useful method to improve fruit quality by altering its exposure to light, whereas its effect on fruit volatiles production is inconsistent, and the genes responsible for the observed changes remain unknown. In the present study, single-layer yellow paper bags were used to study the effects of bagging treatment on the formation of C6 aldehydes in peach fruit (Prunus persica L. Batsch, cv. Yulu) over two succeeding seasons. Higher concentrations of n-hexanal and (E)-2-hexenal, which are characteristic aroma volatiles of peach fruit, were induced by bagging treatment. After bagging treatment, peach fruit had significantly higher LOX and HPL enzyme activities, accompanying increased contents of C6 aldehydes. The gene expression data obtained through real-time PCR showed that no consistent significant differences in transcript levels of LOX genes were observed over the two seasons, but significantly up-regulated expression was found for PpHPL1 after bagging treatment In addition, bagging-treated fruit produced more (E)-2-hexenal and had higher expression levels of PpHPL1 during postharvest ripening at room temperature. The regulatory role of the LOX-HPL pathway on the biosynthesis of n-hexanal and (E)-2-hexenal in response to bagging treatment during peach fruit development is discussed in the text.
[Show abstract][Hide abstract] ABSTRACT: A hypoxic environment is generally undesirable for most plants and stimulates anaerobic metabolism. It is a beneficial treatment, however, for the removal of astringency from persimmon to improve the fruit quality after harvest. High soluble tannins (SCTs) content is one of most important causes of astringency. High CO2 (95%) treatment effectively reduced SCTs in both "Mopan" and "Gongcheng-shuishi" persimmon fruit by causing increases in acetaldehyde. Using RNA-seq and realtime PCR, twelve ethylene response factor genes (DkERF11-22) were isolated and characterized, to determine those responsive to high CO2 treatment. Only two genes, DkERF19 and DkERF22, showed trans-activation effects on the promoters of deastringency-related genes pyruvate decarboxylase genes (DkPDC2 and DkPDC3) and the transcript levels of these genes was enhanced by hypoxia. Moreover, DkERF19 and the previously isolated DkERF9 had additive effects on activating the DkPDC2 promoter. Taken together, these results provide further evidence that transcriptome changes in the level of DkERF mRNAs regulate deastringency-related genes and their role in the mechanism of persimmon fruit deastringency is discussed.
PLoS ONE 01/2014; 9(5):e97043. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Peach fruits are sensitive to chilling injury (CI) during postharvest cold storage and their subsequent shelf-life, which results in loss of quality and market value. Many studies have examined the development of CI, including analyses of changes in biochemical composition, enzyme activity and gene expression; however, the molecular mechanism of CI remains unresolved. Six C-repeat (CRT) / dehydration-responsive element (DRE) binding factor (CBF) genes (PpCBF1-6) were isolated and characterized in peach fruit based on their homology to CBF genes that are available in public Prunus persica genome databases. The expression patterns of these genes were analyzed in response to varying temperatures and durations of treatment. Transcription of PpCBF1/5/6 was induced at low temperatures, whereas expression of other CBF genes remained relatively constant. The results presented here indicate that treating peach fruit with a CI-delaying temperature (0 °C) resulted in a greater accumulation of PpCBF1/5/6 transcripts than that observed in fruit treated with a CI-inducing temperature (5 °C). CBF gene induction was accompanied by a decrease in CI symptoms, including a loss of firmness, flesh browning and increased electrical conductivity, throughout the experimental 21-day cold storage period. An analysis of the upstream nucleotide sequence of CBF genes showed that a cis element inducer of CBF expression 1 (ICEr1) was detected in the promoter of PpCBF1/5/6.
[Show abstract][Hide abstract] ABSTRACT: Anthocyanins, being important for both plant functions and human health, were transcriptionally regulated by the MYB–bHLH–WD40 transcription complex. The key MYB regulator for Chinese bayberry (Myrica rubra), MrMYB1, has been characterized in previous studies, while the specific bHLH partner(s) are unknown. In this study, MrbHLH1 and MrbHLH2 were isolated based on their homology to known plant bHLHs involved in anthocyanin biosynthesis regulation. Coordinate expression of MrbHLH1 with MrMYB1 and the anthocyanin biosynthetic genes was observed during fruit development, while MrbHLH2 showed a weaker correlation. Further transient assays in tobacco leaves suggested that MrbHLH1, but not MrbHLH2, was associated with MrMYB1 and triggered significant anthocyanin production. The lack of function of the MrbHLH2 in anthocyanin biosynthesis regulation suggested that different MrbHLH genes within the same phylogenic subfamily have different functions. Overexpression of MrMYB1 and MrbHLH1 in tobacco confirmed the crucial role of MrMYB1–MrbHLH1 in anthocyanin biosynthesis and all of the structural genes from NtCHS were up-regulated by the complex. Dual luciferase assays, however, indicated that MrMYB1 and MrbHLH1 selectively activated five of the eight promoters of biosynthetic genes from bayberry (MrCHI, MrF3′H, MrDFR1, MrANS, MrUFGT), although expression levels of all eight biosynthetic genes including MrCHS and downstream genes were coordinately increased during fruit ripening. Moreover, the interaction between MrbHLH1 and MrMYB1 was confirmed by yeast two-hybrid assay. In conclusion, MrbHLH1, but not MrbHLH2, was the essential partner of MrMYB1 during anthocyanin biosynthesis regulation in tobacco and bayberry, however, the biosynthetic genes in these two species responded differently to the MrMYB1–MrbHLH1 complex.
Plant Cell Tissue and Organ Culture 12/2013; · 2.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Codon usage analysis has been a classical topic for decades and has significances for studies of evolution, mRNA translation, and new gene discovery, etc. While the codon usage varies among different members of the plant kingdom, indicating the necessity for species-specific study, this work has mostly been limited to model organisms. Recently, the development of deep sequencing, especial RNA-Seq, has made it possible to carry out studies in non-model species.Result: RNA-Seq data of Chinese bayberry was analyzed to investigate the bias of codon usage and codon pairs. High frequency codons (AGG, GCU, AAG and GAU), as well as low frequency ones (NCG and NUA codons) were identified, and 397 high frequency codon pairs were observed. Meanwhile, 26 preferred and 141 avoided neighboring codon pairs were also identified, which showed more significant bias than the same pairs with one or more intervening codons. Codon patterns were also analyzed at the plant kingdom, organism and gene levels. Changes during plant evolution were evident using RSCU (relative synonymous codon usage), which was even more significant than GC3s (GC content of 3rd synonymous codons). Nine GO categories were differentially and independently influenced by CAI (codon adaptation index) or GC3s, especially in 'Molecular function' category. Within a gene, the average CAI increased from 0.720 to 0.785 in the first 50 codons, and then more slowly thereafter. Furthermore, the preferred as well as avoided codons at the position just following the start codon AUG were identified and discussed in relation to the key positions in Kozak sequences.
A comprehensive codon usage Table and number of high-frequency codon pairs were established. Bias in codon usage as well as in neighboring codon pairs was observed, and the significance of this in avoiding DNA mutation, increasing protein production and regulating protein synthesis rate was proposed. Codon usage patterns at three levels were revealed and the significance in plant evolution analysis, gene function classification, and protein translation start site predication were discussed. This work promotes the study of codon biology, and provides some reference for analysis and comprehensive application of RNA-Seq data from other non-model species.
[Show abstract][Hide abstract] ABSTRACT: The persimmon fruit is a particularly good model for studying fruit response to hypoxia, in particular, the hypoxia-response ERF (HRE) genes. An anaerobic environment reduces fruit astringency by converting soluble condensed tannins (SCTs) into an insoluble form. Although the physiology of de-astringency has been widely studied, its molecular control is poorly understood. Both CO(2) and ethylene treatments efficiently removed the astringency from 'Mopan' persimmon fruit, as indicated by a decrease in SCTs. Acetaldehyde, the putative agent for causing de-astringency, accumulated during these treatments, as did activities of the key enzymes of acetaldehyde synthesis, alcohol dehydrogenase (ADH), and pyruvate decarboxylase (PDC). Eight DkADH and DkPDC genes were isolated, and three candidates for a role in de-astringency, DkADH1, DkPDC1, and DkPDC2, were characterized by transcriptional analysis in different tissues. The significance of these specific isoforms was confirmed by principal component analysis. Transient expression in leaf tissue showed that DkPDC2 decreased SCTs. Interactions of six hypoxia-responsive ERF genes and target promoters were tested in transient assays. The results indicated that two hypoxia-responsive ERF genes, DkERF9 and DkERF10, were involved in separately regulating the DkPDC2 and DkADH1 promoters. It is proposed that a DkERF-DkADH/DkPDC cascade is involved in regulating persimmon de-astringency.
Journal of Experimental Botany 10/2012; · 5.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Chinese bayberry (Myrica rubra Sieb. and Zucc.) is an important subtropical fruit crop and an ideal species for fruit quality research due to the rapid and substantial changes that occur during development and ripening, including changes in fruit color and taste. However, research at the molecular level is limited by a lack of sequence data. The present study was designed to obtain transcript sequence data and examine gene expression in bayberry developing fruit based on RNA-Seq and bioinformatic analysis, to provide a foundation for understanding the molecular mechanisms controlling fruit quality changes during ripening.
RNA-Seq generated 1.92 G raw data, which was then de novo assembled into 41,239 UniGenes with a mean length of 531 bp. Approximately 80% of the UniGenes (32,805) were annotated against public protein databases, and coding sequences (CDS) of 31,665 UniGenes were determined. Over 3,600 UniGenes were differentially expressed during fruit ripening, with 826 up-regulated and 1,407 down-regulated. GO comparisons between the UniGenes of these two types and interactive pathways (Ipath) analysis found that energy-related metabolism was enhanced, and catalytic activity was increased. All genes involved in anthocyanin biosynthesis were up-regulated during the fruit ripening processes, concurrent with color change. Important changes in carbohydrate and acid metabolism in the ripening fruit are likely associated with expression of sucrose phosphate synthase (SPS) and glutamate decarboxylase (GAD).
Mass sequence data of Chinese bayberry was obtained and the expression profiles were examined during fruit ripening. The UniGenes were annotated, providing a platform for functional genomic research with this species. Using pathway mapping and expression profiles, the molecular mechanisms for changes in fruit color and taste during ripening were examined. This provides a reference for the study of complicated metabolism in non-model perennial species.
[Show abstract][Hide abstract] ABSTRACT: Thirteen ethylene signaling related genes were isolated and studied during ripening of non-astringent 'Yangfeng' and astringent 'Mopan' persimmon fruit. Some of these genes were characterized as ethylene responsive. Treatments, including ethylene and CO(2), had different effects on persimmon ripening, but overlapping roles in astringency removal, such as increasing the reduction in levels of soluble tannins. DkERS1, DkETR2, and DkERF8, may participate in persimmon fruit ripening and softening. The expression patterns of DkETR2, DkERF4, and DkERF5 had significant correlations with decreases in soluble tannins in 'Mopan' persimmon fruit, suggesting that these genes might be key components in persimmon fruit astringency removal and be the linkage between different treatments, while DkERF1 and DkERF6 may be specifically involved in CO(2) induced astringency removal. The possible roles of ethylene signaling genes in persimmon fruit astringency removal are discussed.
[Show abstract][Hide abstract] ABSTRACT: Three ethylene biosynthesis related genes, EjACS1, EjACO1, and EjACO2, were cloned from the non-climacteric loquat fruit (Eriobotrya japonica Lindl. cv. Luoyangqing). Real-time quantitative PCR (Q-PCR) analysis showed the specific expression of the EjACS1 and EjACO1 genes in fruit, whereas EjACO2 was also expressed in leaves and petals. The expression pattern of EjACO2 was consistent with ethylene production during fruit development, which reached a peak when the fruit color was turning. EjACS1, EjACO1, and EjACO2 all showed low transcript levels throughout 20 °C storage in the postharvest ripening loquat. This is the first time that the expression of ethylene biosynthesis related genes has been studied in loquat fruit. Climacteric increases in ethylene production and respiration rate were observed during the development of loquat fruit, and EjACO2 may play an important role in this process.Highlights► Ripening of non-climacteric loquat fruit may be regulated by ethylene biosynthesis. ► Climacteric increase in ethylene synthesis was observed during loquat development. ► Climacteric increases in respiration rate were observed during loquat development. ► EjACO2 may play an important role in loquat ethylene biosynthesis.
Scientia Horticulturae 01/2011; 130(2):452-458. · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Kiwifruit (Actinidia deliciosa) is a climacteric fruit sensitive to low concentrations of ethylene. To investigate the transcriptional mechanisms underlying kiwifruit ethylene response, transcription factors encoding four EIN3-Like (EILs) and 14 Ethylene Response Factors (ERFs) were cloned from kiwifruit. Expression of these transcription factors was examined during fruit development. The expression of transcripts of most AdERFs was higher during early fruit development, with the exception of AdERF3, which increased with maturity. Several AdERFs were apparently down-regulated by ethylene, as they were affected by the ethylene inhibitor 1-methylcyclopropene and by antisense suppression of ACO (for 1-aminocyclopropane-1-carboxylic acid oxidase) in the fruit. In contrast, AdEILs were constitutively expressed during fruit development and ripening. The transcription factors AdEIL2 and AdEIL3 activated transcription of the ripening-related genes AdACO1 and AdXET5 (xyloglucan endotransglycosylase gene) and, when overexpressed in Arabidopsis (Arabidopsis thaliana), stimulated ethylene production. The potential repressor AdERF9 suppressed this promoter activity. These results support a role for kiwifruit EILs and ERFs in transcriptional regulation of ripening-related genes and in the regulation of kiwifruit fruit-ripening processes.
[Show abstract][Hide abstract] ABSTRACT: During postharvest ripening of kiwifruit [ Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson var. deliciosa cv. Bruno] at 20 degrees C, six lipoxygenase (LOX) genes exhibited different expression patterns. AdLox1 and AdLox5 were up-regulated during ripening, and transcript accumulation was delayed by 1-methylcyclopropene (1-MCP), whereas AdLox2, AdLox3, AdLox4, and AdLox6 were down-regulated with ripening. Levels of two volatiles arising from the LOX pathway, that is, n-hexanal and (E)-2-hexenal, were highest after harvest and declined during ripening at 20 degrees C, whereas the characteristic kiwifruit esters ethyl and methyl butanoate levels increased late in the ripening process. Individual fatty acid concentrations underwent little change during ripening, with linoleic (LA) and linolenic (LeA) acids constituting about 40% of the total. Application of LA and LeA to kiwifruit flesh disks promoted LOX activity and n-hexanal and (E)-2-hexenal generation, whereas inhibitors of LOX, n-propyl gallate (n-PG) and nordihydroguariaretic acid (NDGA), caused a parallel reduction in enzyme activity and in the production of C6 aldehydes. The six LOX genes showed different sensitivities to the LOX substrates and inhibitors. The ethylene up-regulated genes AdLox1 and AdLox5 were induced by LA and LeA and inhibited by n-PG and NDGA. Of the LOX genes that were down-regulated by ethylene, only AdLox4 and AdLox6 were stimulated in response to the substrates and retarded by the inhibitors. The possible roles of the six LOX genes in kiwifruit ripening and aroma development are discussed.
Journal of Agricultural and Food Chemistry 05/2009; 57(7):2875-81. · 3.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to follow expression of ethylene signalling genes during storage and ripening of kiwifruit at low temperature. Kiwifruit (Actinidia deliciosa [A. Chev.] C.F. Liang et A.R. Ferguson var. deliciosa cv. Hayward) were stored at 0 °C for 12 weeks, followed by 6 d of shelf-life at 20 °C. Fruit ripened and softened slowly during storage at 0 °C, and no ethylene was detectable at the end of storage or during shelf-life. Five ethylene receptor genes, two CTR1-like genes and four EIN3-like genes showed different changes in expression during low temperature storage. Those genes showing altered expression could be divided into three groups: AdERS1a, AdETR2, AdETR3, AdCTR1 and four EIN3-like genes were up-regulated, while AdERS1b and AdETR1 were suppressed, and AdCTR2 was largely unchanged. On transfer to 20 °C shelf-life, most genes showed no substantial change, except for AdETR3 which was suppressed and AdETR1 and AdERS1b which were up-regulated. These gene expression patterns are indicative of specific and differential gene responses to low temperature during kiwifruit ripening.
[Show abstract][Hide abstract] ABSTRACT: Gene families associated with the ethylene signal transduction pathway in ripening kiwifruit (Actinidia deliciosa [A. Chev.] C.F. Liang et A.R. Ferguson var. deliciosa cv. Hayward) were isolated from a kiwifruit expressed sequence tag (EST) database, including five ethylene receptor genes, two CTR1-like genes, and an EIN3-like gene AdEIL1. All were differentially expressed among various kiwifruit vine tissues, and none was fruit specific. During fruit development, levels of transcripts of AdERS1a, AdETR3, and the two CTR1-like genes decreased, whereas those of AdERS1b and AdETR2 peaked at 97 d after full bloom. In ripening kiwifruit, there was a diverse response of the ethylene receptor family to internal and external ethylene. AdERS1a, AdETR2, and AdETR3 expression increased at the climacteric stage and transcripts were induced by external ethylene treatment, while AdERS1b showed no response to ethylene. AdETR1 was negatively regulated by internal and external ethylene in ripening fruit. The two CTR1-like genes also had different expression patterns, with AdCTR1 increasing at the climacteric stage and AdCTR2 undergoing little change. 1-Methylcyclopropene treatment prevented the ethylene response of all components, but transient down-regulation was only found with AdETR2 and AdCTR1. Similar gene and ethylene responses were found in both fruit flesh and core tissues. The ethylene-induced down-regulation of AdETR1 suggests that it may have a role in sensing ethylene and transmitting this response to other members of the receptor family, thus activating the signal transduction pathway.
Journal of Experimental Botany 02/2008; 59(8):2097-108. · 5.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effects of acetylsalicylic acid (ASA) on kiwifruit (Actinidia deliciosa cvs Bruno and Hayward) ethylene biosynthesis and signaling were investigated. Exogenous application of ASA inhibited ethylene production in both whole fruit, and in vitro with flesh discs, and enzymes associated with ethylene biosynthesis (ACS and ACO). The effect of ASA treatment on kiwifruit softening was relatively weak. Combination treatments also had inhibitory effects on fruit ripening, with ASA + C2H4 more effective than C2H4 + ASA. In order to evaluate the effects of ASA on ethylene signaling, twenty-four ethylene signaling components (five ethylene receptors, two CTR1 like genes, four EIN3-like genes and thirteen ERF genes) were analyzed at the transcriptional level. The results indicated that ASA treatment generally inhibited ethylene-induced modulation of ethylene receptor genes, and had little effect on softening-related ethylene signaling components, which suggested that ASA inhibits fruit ripening mainly by interfering directly with ethylene biosynthesis and perception. In addition, the ethylene response factors AdERF1, AdERF3 and AdERF12 were characterized as ASA-responsive genes, and their roles in fruit stress response are also discussed.
[Show abstract][Hide abstract] ABSTRACT: Organic acid and sugar balance is an important trait for fruit quality. The mandarin, Ponkan (Citrus reticulata Blanco cv. Ponkan) is rich in organic acids even at maturity, thus the fruit provide good material for the study of organic acid degradation. In the present research, hot air (40 °C, 2 d) treatment (HAT) was found to have significant effects on both degradation of the organic acids, especially on citric acid, and accumulation of soluble sugars, especially on fructose and glucose. Genes related to citric acid degradation related (CitAco1, CitAco2, CitAco3, CitIDH1, CitIDH2, CitIDH3, CitGAD4, CitGAD5 and CitGS2) and sucrose metabolism (CitAI1, CitAI3, CitNI1 and CitNI3) were isolated and transcription analyzed. HAT significantly up-regulated CitAco3, CitIDH2/3 and CitGAD4 expression, while having little effect on CitGS2. Sucrose metabolism related genes also differentially responded to HAT, with CitAI genes were induced and CitNI genes were relatively unchanged. It is proposed that HAT drove citric acid degradation via the GABA shunt pathway (especially by modulating CitAco3–CitIDH2/3–CitGAD4 cascade), but not the glycolysis pathway.
Scientia Horticulturae 147:118–125. · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ethylene response factors (ERFs) play important roles in fruit ripening and abiotic stress response. After harvest, fruit such as kiwifruit are subject to a range of stresses associated with postharvest handling and storage treatments. There have been few attempts to evaluate fruit ERF responses in relation to such abiotic stress. Stress treatments including low temperature (0 °C), high temperature (35 °C), high CO2 (5%) and high water loss (∼10% RH air) were applied to freshly harvested mature kiwifruit. Expression patterns of 13 AdERF genes were followed. In response to the abiotic stresses, AdERF3, AdERF4, AdERF11, AdERF12 and AdERF14 were constitutively up-regulated, and AdERF1 was generally down-regulated, while the other AdERF genes showed no regular expression patterns. These data showed that AdERF genes differentially respond to abiotic stresses experienced by fruit during postharvest storage.
[Show abstract][Hide abstract] ABSTRACT: MrMYB1, an R2R3 MYB transcription factor (TF) gene associated with anthocyanin biosynthesis in Chinese bayberry (Myrica rubra Sieb. and Zucc.), was introduced into Arabidopsis and tobacco (Nicotiana tabacum) under the control of the CaMV 35S promoter. Overexpression of MrMYB1 induced anthocyanin accumulation in all tissues of Arabidopsis as well as in petals, ovaries and young seeds of tobacco, but not in tobacco leaves. The anthocyanin biosynthetic pathway, including chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR) and anthocyanidin synthase (ANS), and the basic helix-loop-helix (bHLH) transcriptional partner TRANSPARENT TESTA8 (TT8), were up-regulated significantly in MrMYB1-overexpressing Arabidopsis. In MrMYB1-overexpressing tobacco petals, ovaries and young seeds, anthocyanin biosynthetic genes and bHLH partners NtAn1a and NtAn1b, were up-regulated. In contrast, high expression of MrMYB1 in transgenic tobacco leaves did not induce the expression of anthocyanin biosynthesis. Unlike in petals and ovaries, the foliar transcript level of NtAn1a and NtAn1b was extremely low and not stimulated by MrMYB1 transformation. These results show that higher expression of an endogenous bHLH partner, either intrinsically or stimulated by exogenous gene transformation, is required for anthocyanin production in plant tissues, and the different abundance in endogenous bHLH transcript accounts for differential accumulation of anthocyanin in Arabidopsis and tobacco leaves. These findings demonstrate that higher levels of expression of an endogenous bHLH partner, either intrinsically or following genetic transformation, are required for anthocyanin production in plant tissues. Moreover, differences in levels of endogenous bHLH transcripts account for observed differential accumulation of anthocyanin in leaves of Arabidopsis and tobacco.
Plant Cell Tissue and Organ Culture 113(3). · 2.61 Impact Factor