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Tc-MYBPA an Arabidopsis TT2-like transcription factor and functions in the regulation of proanthocyanidin synthesis in Theobroma cacao.

Liu Y, Shi Z, Maximova SN, Payne MJ, Guiltinan MJ - BMC Plant Biol. (2015)

Bottom Line: These compounds have been associated with several health benefits in humans.We observed that overexpression of the Tc-MYBPA gene resulted in increased expression of several key genes encoding the major structural enzymes of the PA and anthocyanidin pathway, including DFR (dihydroflavanol reductase), LDOX (leucoanthocyanidin dioxygenase) and BAN (ANR, anthocyanidin reductase).We conclude that the Tc-MYBPA gene that encodes an R2R3 type MYB transcription factor is an Arabidopsis TT2 like transcription factor, and may be involved in the regulation of both anthocyanin and PA synthesis in cacao.

View Article: PubMed Central - PubMed

Affiliation: Huck Institute of Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA. dr.yiliu@gmail.com.

ABSTRACT

Background: The flavan-3-ols catechin and epicatechin, and their polymerized oligomers, the proanthocyanidins (PAs, also called condensed tannins), accumulate to levels of up to 15 % of the total weight of dry seeds of Theobroma cacao L. These compounds have been associated with several health benefits in humans. They also play important roles in pest and disease defense throughout the plant. In Arabidopsis, the R2R3 type MYB transcription factor TT2 regulates the major genes leading to the synthesis of PA.

Results: To explore the transcriptional regulation of the PA synthesis pathway in cacao, we isolated and characterized an R2R3 type MYB transcription factor MYBPA from cacao. We examined the spatial and temporal gene expression patterns of the Tc-MYBPA gene and found it to be developmentally expressed in a manner consistent with its involvement in PAs and anthocyanin synthesis. Functional complementation of an Arabidopsis tt2 mutant with Tc-MYBPA suggested that it can functionally substitute the Arabidopsis TT2 gene. Interestingly, in addition to PA accumulation in seeds of the Tc-MYBPA expressing plants, we also observed an obvious increase of anthocyanidin accumulation in hypocotyls. We observed that overexpression of the Tc-MYBPA gene resulted in increased expression of several key genes encoding the major structural enzymes of the PA and anthocyanidin pathway, including DFR (dihydroflavanol reductase), LDOX (leucoanthocyanidin dioxygenase) and BAN (ANR, anthocyanidin reductase).

Conclusion: We conclude that the Tc-MYBPA gene that encodes an R2R3 type MYB transcription factor is an Arabidopsis TT2 like transcription factor, and may be involved in the regulation of both anthocyanin and PA synthesis in cacao. This research may provide molecular tools for breeding of cacao varieties with improved disease resistance and enhanced flavonoid profiles for nutritional and pharmaceutical applications.

No MeSH data available.


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Semi-quantitative RT-PCR analysis of expression of flavonoid structural genes in young seedlings of the same Arabidopsis lines analyzed in Fig. 6. DFR, dihydroflavonol reductase; LDOX, leucoanthocyanidin dioxygenase; BAN, banyuls (anthocyanidin reductase); UFGT, UDP-Glc flavonoid glucosyltransferase; CHS, chalcone synthase; CHI, chalcone isomerase; F3H, flavonoid 3’-hydroxylase; FLS, flavonol synthase, UBi, Ubiquitin
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Fig8: Semi-quantitative RT-PCR analysis of expression of flavonoid structural genes in young seedlings of the same Arabidopsis lines analyzed in Fig. 6. DFR, dihydroflavonol reductase; LDOX, leucoanthocyanidin dioxygenase; BAN, banyuls (anthocyanidin reductase); UFGT, UDP-Glc flavonoid glucosyltransferase; CHS, chalcone synthase; CHI, chalcone isomerase; F3H, flavonoid 3’-hydroxylase; FLS, flavonol synthase, UBi, Ubiquitin

Mentions: In order to confirm that Tc-MYBPA activates PA synthesis genes, we used semi-quantitative RT-PCR to examine the expression of relevant genes in young seedlings of transgenic Tc-MYBPA-tt2 lines, untransformed tt2 mutant and wild-type plants (Fig. 8). Expression levels were measured for the PA-related structural genes (DFR, LDOX and BAN) as well as the general flavonoid pathway genes (chalcone synthase, CHS; chalcone isomerase, CHI; and flavonoid 3'-hydroxylase, F3H), a flavonol-specific gene (flavonol synthase; FLS) and an anthocyanin-specific gene (UDP-Glc-flavonoid glucosyltransferase, UFGT). Gene expression of DFR and LDOX was at about the same level as in the wild-type (Col-0) control and the tt2 mutant, a result consistent with their contribution to anthocyanidin synthesis. In all transgenic lines, overexpression of Tc-MYBPA was found to activate the flavonoid late biosynthesis genes [10] related to PA synthesis (DFR, LDOX and BAN). There was a 2-fold increase of DFR gene expression in all transgenic lines, and an approximate 1.5-1.7-fold increase of LDOX gene expression. BAN was not expressed in either tt2 or Col-0 seedlings but it was significantly activated in the transgenic lines, suggesting that Tc-MYBPA controls its activation. However, no significant gene activation was detected for all the other flavonoid genes including CHS, CHI, F3H representing the general flavonoid pathway, FLS representing the flavonol-specific pathway and UFGT representing the anthocyanin-specific pathway.Fig. 8


Tc-MYBPA an Arabidopsis TT2-like transcription factor and functions in the regulation of proanthocyanidin synthesis in Theobroma cacao.

Liu Y, Shi Z, Maximova SN, Payne MJ, Guiltinan MJ - BMC Plant Biol. (2015)

Semi-quantitative RT-PCR analysis of expression of flavonoid structural genes in young seedlings of the same Arabidopsis lines analyzed in Fig. 6. DFR, dihydroflavonol reductase; LDOX, leucoanthocyanidin dioxygenase; BAN, banyuls (anthocyanidin reductase); UFGT, UDP-Glc flavonoid glucosyltransferase; CHS, chalcone synthase; CHI, chalcone isomerase; F3H, flavonoid 3’-hydroxylase; FLS, flavonol synthase, UBi, Ubiquitin
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4481123&req=5

Fig8: Semi-quantitative RT-PCR analysis of expression of flavonoid structural genes in young seedlings of the same Arabidopsis lines analyzed in Fig. 6. DFR, dihydroflavonol reductase; LDOX, leucoanthocyanidin dioxygenase; BAN, banyuls (anthocyanidin reductase); UFGT, UDP-Glc flavonoid glucosyltransferase; CHS, chalcone synthase; CHI, chalcone isomerase; F3H, flavonoid 3’-hydroxylase; FLS, flavonol synthase, UBi, Ubiquitin
Mentions: In order to confirm that Tc-MYBPA activates PA synthesis genes, we used semi-quantitative RT-PCR to examine the expression of relevant genes in young seedlings of transgenic Tc-MYBPA-tt2 lines, untransformed tt2 mutant and wild-type plants (Fig. 8). Expression levels were measured for the PA-related structural genes (DFR, LDOX and BAN) as well as the general flavonoid pathway genes (chalcone synthase, CHS; chalcone isomerase, CHI; and flavonoid 3'-hydroxylase, F3H), a flavonol-specific gene (flavonol synthase; FLS) and an anthocyanin-specific gene (UDP-Glc-flavonoid glucosyltransferase, UFGT). Gene expression of DFR and LDOX was at about the same level as in the wild-type (Col-0) control and the tt2 mutant, a result consistent with their contribution to anthocyanidin synthesis. In all transgenic lines, overexpression of Tc-MYBPA was found to activate the flavonoid late biosynthesis genes [10] related to PA synthesis (DFR, LDOX and BAN). There was a 2-fold increase of DFR gene expression in all transgenic lines, and an approximate 1.5-1.7-fold increase of LDOX gene expression. BAN was not expressed in either tt2 or Col-0 seedlings but it was significantly activated in the transgenic lines, suggesting that Tc-MYBPA controls its activation. However, no significant gene activation was detected for all the other flavonoid genes including CHS, CHI, F3H representing the general flavonoid pathway, FLS representing the flavonol-specific pathway and UFGT representing the anthocyanin-specific pathway.Fig. 8

Bottom Line: These compounds have been associated with several health benefits in humans.We observed that overexpression of the Tc-MYBPA gene resulted in increased expression of several key genes encoding the major structural enzymes of the PA and anthocyanidin pathway, including DFR (dihydroflavanol reductase), LDOX (leucoanthocyanidin dioxygenase) and BAN (ANR, anthocyanidin reductase).We conclude that the Tc-MYBPA gene that encodes an R2R3 type MYB transcription factor is an Arabidopsis TT2 like transcription factor, and may be involved in the regulation of both anthocyanin and PA synthesis in cacao.

View Article: PubMed Central - PubMed

Affiliation: Huck Institute of Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA. dr.yiliu@gmail.com.

ABSTRACT

Background: The flavan-3-ols catechin and epicatechin, and their polymerized oligomers, the proanthocyanidins (PAs, also called condensed tannins), accumulate to levels of up to 15 % of the total weight of dry seeds of Theobroma cacao L. These compounds have been associated with several health benefits in humans. They also play important roles in pest and disease defense throughout the plant. In Arabidopsis, the R2R3 type MYB transcription factor TT2 regulates the major genes leading to the synthesis of PA.

Results: To explore the transcriptional regulation of the PA synthesis pathway in cacao, we isolated and characterized an R2R3 type MYB transcription factor MYBPA from cacao. We examined the spatial and temporal gene expression patterns of the Tc-MYBPA gene and found it to be developmentally expressed in a manner consistent with its involvement in PAs and anthocyanin synthesis. Functional complementation of an Arabidopsis tt2 mutant with Tc-MYBPA suggested that it can functionally substitute the Arabidopsis TT2 gene. Interestingly, in addition to PA accumulation in seeds of the Tc-MYBPA expressing plants, we also observed an obvious increase of anthocyanidin accumulation in hypocotyls. We observed that overexpression of the Tc-MYBPA gene resulted in increased expression of several key genes encoding the major structural enzymes of the PA and anthocyanidin pathway, including DFR (dihydroflavanol reductase), LDOX (leucoanthocyanidin dioxygenase) and BAN (ANR, anthocyanidin reductase).

Conclusion: We conclude that the Tc-MYBPA gene that encodes an R2R3 type MYB transcription factor is an Arabidopsis TT2 like transcription factor, and may be involved in the regulation of both anthocyanin and PA synthesis in cacao. This research may provide molecular tools for breeding of cacao varieties with improved disease resistance and enhanced flavonoid profiles for nutritional and pharmaceutical applications.

No MeSH data available.


Related in: MedlinePlus