Dataset Information

MYB44 competitively inhibits the formation of the MYB340-bHLH2-NAC56 complex to regulate anthocyanin biosynthesis in purple-fleshed sweet potato.

ABSTRACT: BACKGROUND:Anthocyanins, which have important biological functions and have a beneficial effect on human health, notably account for pigmentation in purple-fleshed sweet potato tuberous roots. Individual regulatory factors of anthocyanin biosynthesis have been identified; however, the regulatory network of anthocyanin biosynthesis in purple-fleshed sweet potato is unclear. RESULTS:We functionally determined that IbMYB340 cotransformed with IbbHLH2 in tobacco and strawberry receptacles induced anthocyanin accumulation, and the addition of IbNAC56a or IbNAC56b caused increased pigmentation. Furthermore, we confirmed the interaction of IbMYB340 with IbbHLH2 and IbNAC56a or IbNAC56b via yeast two-hybrid and firefly luciferase complementation assays; these proteins could form a MYB340-bHLH2-NAC56a or MYB340-bHLH2-NAC56b transcriptional complex to regulate anthocyanin biosynthesis by binding to the IbANS promoter rather than the IbUFGT promoter. Furthermore, it was found by a transient expression system in tobacco leaves that IbMYB44 could decrease anthocyanin accumulation. Moreover, the interaction of IbMYB44 with IbMYB340 and IbNAC56a or IbNAC56b was verified. This result suggested that IbMYB44 acts as a repressor of anthocyanin in sweet potato. CONCLUSIONS:The repressor IbMYB44 affected anthocyanin biosynthesis by competitively inhibiting the IbMYB340-IbbHLH2-IbNAC56a or IbMYB340-IbbHLH2-IbNAC56b regulatory complex formation. Overall, the present study proposed a novel regulatory network whereby several vital TFs play key roles in regulating anthocyanin biosynthesis, and it provides strong insight into the potential mechanism underlying anthocyanin biosynthesis in sweet potato tuberous roots with purple color.

SUBMITTER: Wei ZZ

PROVIDER: S-EPMC7275474 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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MYB44 competitively inhibits the formation of the MYB340-bHLH2-NAC56 complex to regulate anthocyanin biosynthesis in purple-fleshed sweet potato.

Wei Zeng-Zheng ZZ Hu Kang-Di KD Zhao Dong-Lan DL Tang Jun J Huang Zhong-Qin ZQ Jin Peng P Li Yan-Hong YH Han Zhuo Z Hu Lan-Ying LY Yao Gai-Fang GF Zhang Hua H

BMC plant biology 20200605 1

<h4>Background</h4>Anthocyanins, which have important biological functions and have a beneficial effect on human health, notably account for pigmentation in purple-fleshed sweet potato tuberous roots. Individual regulatory factors of anthocyanin biosynthesis have been identified; however, the regulatory network of anthocyanin biosynthesis in purple-fleshed sweet potato is unclear.<h4>Results</h4>We functionally determined that IbMYB340 cotransformed with IbbHLH2 in tobacco and strawberry recepta ...[more]

PMID: 32503504

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Project description:In various plant species, many transcription factors (TFs), such as MYB, bHLH, and WD40, have been identified as regulators of anthocyanin biosynthesis in underground organs. However, the regulatory elements of anthocyanin biosynthesis in the tuberous roots of sweet potato have not been elucidated yet. Here, we selected the purple-fleshed sweet potato cultivar "Zhezi1" (ZZ P ) and its spontaneous yellow-fleshed mutant "Xinli" (XL Y ) to investigate the regulatory mechanism of the anthocyanin biosynthesis in the tuberous roots of sweet potato. By analyzing the IbMYB1 genotype in ZZ P and XL Y , we found that the IbMYB1-2, a MYB TF involved in anthocyanin biosynthesis, was missing in the XL Y genome, which might lead to an extreme decrease in anthocyanins in XL Y . A comparative transcriptome analysis of ZZ P and XL Y was conducted to find the TFs involved in anthocyanin biosynthesis in ZZ P and XL Y . The anthocyanin structural genes were significantly enriched among the differentially expressed genes. Moreover, one MYB activator (IbMYB1), one bHLH (IbbHLH2), three WRKY activator candidates (IbWRKY21, IbWRKY24, and IbWRKY44), and two MYB repressors (IbMYB27 and IbMYBx-ZZ) were highly expressed in ZZ P accompanied with anthocyanin structural genes. We also tested the expression of these TFs in six purple- and two orange-fleshed sweet potato cultivars. Interestingly, most of these TFs were significantly positively correlated with anthocyanin contents in these cultivars. The function of the anthocyanin biosynthesis repression of IbMYB27 and IbMYBx-ZZ was verified through transient co-transformation with IbMYB1 into tobacco leaves. Further functional verification of the above TFs was conducted by Y2H, BiFC, and dual-luciferase assays. These tests showed that the MYB-bHLH-WD40/MYB-bHLH-WD40-WRKY complex activated the promoter of anthocyanin structural gene IbDFR and promoters for IbWRKY44, IbMYB27, and IbMYBx-ZZ, indicating reinforcement and feedback regulation to maintain the level of anthocyanin accumulation in the tuberous roots of purple-fleshed sweet potato. These results may provide new insights into the regulatory mechanism of anthocyanin biosynthesis and accumulation in underground organs of sweet potatoes.

Dataset Information

MYB44 competitively inhibits the formation of the MYB340-bHLH2-NAC56 complex to regulate anthocyanin biosynthesis in purple-fleshed sweet potato.

Publications

MYB44 competitively inhibits the formation of the MYB340-bHLH2-NAC56 complex to regulate anthocyanin biosynthesis in purple-fleshed sweet potato.

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