The R3-Type MYB Transcription Factor BrMYBL2.1 Negatively Regulates Anthocyanin Biosynthesis in Chinese Cabbage (<i>Brassica rapa</i> L.) by Repressing MYB–bHLH–WD40 Complex Activity

Chinese cabbage (<i>Brassica rapa</i> L.) leaves are purple in color due to anthocyanin accumulation and have nutritional and aesthetic value, as well as antioxidant properties. Here, we identified the R3 MYB transcription factor BrMYBL2.1 as a key negative regulator of anthocyanin biosy...

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Main Authors: JiYeon Kim, Da-Hye Kim, Jong-Yeol Lee, Sun-Hyung Lim
Format: Article
Language:English
Published: MDPI AG 2022-03-01
Series:International Journal of Molecular Sciences
Subjects:
Online Access:https://www.mdpi.com/1422-0067/23/6/3382
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author JiYeon Kim
Da-Hye Kim
Jong-Yeol Lee
Sun-Hyung Lim
author_facet JiYeon Kim
Da-Hye Kim
Jong-Yeol Lee
Sun-Hyung Lim
author_sort JiYeon Kim
collection DOAJ
description Chinese cabbage (<i>Brassica rapa</i> L.) leaves are purple in color due to anthocyanin accumulation and have nutritional and aesthetic value, as well as antioxidant properties. Here, we identified the R3 MYB transcription factor BrMYBL2.1 as a key negative regulator of anthocyanin biosynthesis. A Chinese cabbage cultivar with green leaves harbored a functional BrMYBL2.1 protein, designated BrMYBL2.1-G, with transcriptional repressor activity of anthocyanin biosynthetic genes. By contrast, BrMYBL2.1 from a Chinese cabbage cultivar with purple leaves carried a poly(A) insertion in the third exon of the gene, resulting in the insertion of multiple lysine residues in the predicted protein, designated BrMYBL2.1-P. Although both BrMYBL2.1 variants localized to the nucleus, only BrMYBL2.1-G interacted with its cognate partner BrTT8. Transient infiltration assays in tobacco leaves revealed that BrMYBL2.1-G, but not BrMYBL2.1-P, actively represses pigment accumulation by inhibiting the transcription of anthocyanin biosynthetic genes. Transient promoter activation assay in Arabidopsis protoplasts verified that BrMYBL2.1-G, but not BrMYBL2.1-P, can repress transcriptional activation of <i>BrCHS</i> and <i>BrDFR</i>, which was activated by co-expression with BrPAP1 and BrTT8. We determined that BrMYBL2.1-P may be more prone to degradation than BrMYBL2.1-G via ubiquitination. Taken together, these results demonstrate that BrMYBL2.1-G blocks the activity of the MBW complex and thus represses anthocyanin biosynthesis, whereas the variant BrMYBL2.1-P from purple Chinese cabbage cannot, thus leading to higher anthocyanin accumulation.
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spelling doaj.art-cd2246625e3e432e99009946c6ee2c722023-11-24T01:38:34ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672022-03-01236338210.3390/ijms23063382The R3-Type MYB Transcription Factor BrMYBL2.1 Negatively Regulates Anthocyanin Biosynthesis in Chinese Cabbage (<i>Brassica rapa</i> L.) by Repressing MYB–bHLH–WD40 Complex ActivityJiYeon Kim0Da-Hye Kim1Jong-Yeol Lee2Sun-Hyung Lim3Division of Horticultural Biotechnology, School of Biotechnology, Hankyong National University, Anseong 17579, KoreaDivision of Horticultural Biotechnology, School of Biotechnology, Hankyong National University, Anseong 17579, KoreaNational Institute of Agricultural Sciences, Rural Development Administration, Jeonju 54874, KoreaDivision of Horticultural Biotechnology, School of Biotechnology, Hankyong National University, Anseong 17579, KoreaChinese cabbage (<i>Brassica rapa</i> L.) leaves are purple in color due to anthocyanin accumulation and have nutritional and aesthetic value, as well as antioxidant properties. Here, we identified the R3 MYB transcription factor BrMYBL2.1 as a key negative regulator of anthocyanin biosynthesis. A Chinese cabbage cultivar with green leaves harbored a functional BrMYBL2.1 protein, designated BrMYBL2.1-G, with transcriptional repressor activity of anthocyanin biosynthetic genes. By contrast, BrMYBL2.1 from a Chinese cabbage cultivar with purple leaves carried a poly(A) insertion in the third exon of the gene, resulting in the insertion of multiple lysine residues in the predicted protein, designated BrMYBL2.1-P. Although both BrMYBL2.1 variants localized to the nucleus, only BrMYBL2.1-G interacted with its cognate partner BrTT8. Transient infiltration assays in tobacco leaves revealed that BrMYBL2.1-G, but not BrMYBL2.1-P, actively represses pigment accumulation by inhibiting the transcription of anthocyanin biosynthetic genes. Transient promoter activation assay in Arabidopsis protoplasts verified that BrMYBL2.1-G, but not BrMYBL2.1-P, can repress transcriptional activation of <i>BrCHS</i> and <i>BrDFR</i>, which was activated by co-expression with BrPAP1 and BrTT8. We determined that BrMYBL2.1-P may be more prone to degradation than BrMYBL2.1-G via ubiquitination. Taken together, these results demonstrate that BrMYBL2.1-G blocks the activity of the MBW complex and thus represses anthocyanin biosynthesis, whereas the variant BrMYBL2.1-P from purple Chinese cabbage cannot, thus leading to higher anthocyanin accumulation.https://www.mdpi.com/1422-0067/23/6/3382anthocyaninBrMYBL2.1Chinese cabbageinsertional mutationrepressorubiquitination
spellingShingle JiYeon Kim
Da-Hye Kim
Jong-Yeol Lee
Sun-Hyung Lim
The R3-Type MYB Transcription Factor BrMYBL2.1 Negatively Regulates Anthocyanin Biosynthesis in Chinese Cabbage (<i>Brassica rapa</i> L.) by Repressing MYB–bHLH–WD40 Complex Activity
International Journal of Molecular Sciences
anthocyanin
BrMYBL2.1
Chinese cabbage
insertional mutation
repressor
ubiquitination
title The R3-Type MYB Transcription Factor BrMYBL2.1 Negatively Regulates Anthocyanin Biosynthesis in Chinese Cabbage (<i>Brassica rapa</i> L.) by Repressing MYB–bHLH–WD40 Complex Activity
title_full The R3-Type MYB Transcription Factor BrMYBL2.1 Negatively Regulates Anthocyanin Biosynthesis in Chinese Cabbage (<i>Brassica rapa</i> L.) by Repressing MYB–bHLH–WD40 Complex Activity
title_fullStr The R3-Type MYB Transcription Factor BrMYBL2.1 Negatively Regulates Anthocyanin Biosynthesis in Chinese Cabbage (<i>Brassica rapa</i> L.) by Repressing MYB–bHLH–WD40 Complex Activity
title_full_unstemmed The R3-Type MYB Transcription Factor BrMYBL2.1 Negatively Regulates Anthocyanin Biosynthesis in Chinese Cabbage (<i>Brassica rapa</i> L.) by Repressing MYB–bHLH–WD40 Complex Activity
title_short The R3-Type MYB Transcription Factor BrMYBL2.1 Negatively Regulates Anthocyanin Biosynthesis in Chinese Cabbage (<i>Brassica rapa</i> L.) by Repressing MYB–bHLH–WD40 Complex Activity
title_sort r3 type myb transcription factor brmybl2 1 negatively regulates anthocyanin biosynthesis in chinese cabbage i brassica rapa i l by repressing myb bhlh wd40 complex activity
topic anthocyanin
BrMYBL2.1
Chinese cabbage
insertional mutation
repressor
ubiquitination
url https://www.mdpi.com/1422-0067/23/6/3382
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