title: Overexpression of the IbMYB1 gene in an orange-fleshed sweet potato cultivar produces a dual-pigmented transgenic sweet potato with improved antioxidant activity.
abstract: The R2R3-type protein IbMYB1 is a key regulator of anthocyanin biosynthesis in the storage roots of sweet potato [Ipomoea batatas (L.) Lam]. Previously, we demonstrated that IbMYB1 expression stimulated anthocyanin pigmentation in tobacco leaves and Arabidopsis. Here, we generated dual-pigmented transgenic sweet potato plants that accumulated high levels of both anthocyanins and carotenoids in a single sweet potato storage root. An orange-fleshed cultivar with high carotenoid levels was transformed with the IbMYB1 gene under the control of either the storage root-specific sporamin 1 (SPO1) promoter or the oxidative stress-inducible peroxidase anionic 2 (SWPA2) promoter. The SPO1-MYB transgenic lines exhibited higher anthocyanin levels in storage roots than empty vector control (EV) or SWPA2-MYB plants, but carotenoid content was unchanged. SWPA2-MYB transgenic lines exhibited higher levels of both anthocyanin and carotenoids than EV plants. Analysis of hydrolyzed anthocyanin extracts indicated that cyanidin and peonidin predominated in both overexpression lines. Quantitative reverse transcription-polymerase chain reaction analysis demonstrated that IbMYB1 expression in both IbMYB1 transgenic lines strongly induced the upregulation of several genes in the anthocyanin biosynthetic pathway, whereas the expression of carotenoid biosynthetic pathway genes varied between transgenic lines. Increased anthocyanin levels in transgenic plants also promoted the elevation of proanthocyanidin and total phenolic levels in fresh storage roots. Consequently, all IbMYB1 transgenic plants displayed much higher antioxidant activities than EV plants. In field cultivations, storage root yields varied between the transgenic lines. Taken together, our results indicate that overexpression of IbMYB1 is a highly promising strategy for the generation of transgenic plants with enhanced antioxidant capacity.
authors.affiliation: Plant Systems Engineering Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Korea; Department of Green Chemistry and Environmental Biotechnology, University of Science & Technology (UST), Daejeon, Korea.
authors.forename: Sung-Chul
authors.initials: SC
authors.lastname: Park
authors.forename: Yun-Hee
authors.initials: YH
authors.lastname: Kim
authors.forename: Sun Ha
authors.initials: SH
authors.lastname: Kim
authors.forename: Yu Jeong
authors.initials: YJ
authors.lastname: Jeong
authors.forename: Cha Young
authors.initials: CY
authors.lastname: Kim
authors.forename: Joon Seol
authors.initials: JS
authors.lastname: Lee
authors.forename: Ji-Yeong
authors.initials: JY
authors.lastname: Bae
authors.forename: Mi-Jeong
authors.initials: MJ
authors.lastname: Ahn
authors.forename: Jae Cheol
authors.initials: JC
authors.lastname: Jeong
authors.forename: Haeng-Soon
authors.initials: HS
authors.lastname: Lee
authors.forename: Sang-Soo
authors.initials: SS
authors.lastname: Kwak
mesh_terms: D000872:Anthocyanins / Q000378:metabolism*; D000975:Antioxidants / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism*; D015870:Gene Expression; D027723:Ipomoea batatas / Q000235:genetics* / Q000378:metabolism; D009928:Organ Specificity; D010084:Oxidation-Reduction; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D014026:Nicotiana / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D000872:Anthocyanins; D000975:Antioxidants; D010940:Plant Proteins; D014157:Transcription Factors; D002338:Carotenoids