Page 168 - 《广西植物》2025年第7期
P. 168

1 3 6 0                                广  西  植  物                                         45 卷
             ( 1. School of Tropical Agriculture and Forestryꎬ Hainan Universityꎬ Danzhou 571737ꎬ Hainanꎬ Chinaꎻ 2. Key Laboratory of Crop Gene Resources
                and Germplasm Enhancement in Southern Chinaꎬ Ministry of Agriculture and Rural Affairsꎬ Key Laboratory of Tropical Crops Germplasm
                Resources Genetic Improvement and Innovation of Hainan Provinceꎬ The Engineering Technology Research Center of Tropical Ornamental
                             Plant Germplasm Innovation and Utilizationꎬ Tropical Crops Genetic Resources Instituteꎬ Chinese
                                      Academy of Tropical Agricultural Sciencesꎬ Haikou 571101ꎬ China )

                 Abstract: Carotenoids is one of the important floral pigments in Phalaenopsis ̄type Dendrobium hybrids (Den ̄Phals). In
                 order to explore the biosynthesis of carotenoids in Den ̄Phals flowers two key synthase genes DhLCYB and DhLCYE on the
                 downstream branch of carotenoid synthesis pathway were cloned from the flower buds of Den ̄Phals cultivar Dendrobium
                 ‘Thongchai Gold’ꎬ and their sequences were analyzedꎬ and their expression characteristics at different stages of flower
                 development in Den ̄Phals with different flower colors were measured using RT ̄qPCRꎬ and their correlation with the
                 composition and content of carotenoids were analyzedꎬ which were investigated through targeted metabolomics assay. The
                 results were as follows: (1) Transcripts of DhLCYB and DhLCYE genes were cloned. Their amino acid sequences showed
                 the highest homology to those of species of the same genusꎬ D. candidum and D. chrysotoxumꎬ showed the highest
                 homology. As two lycopene cyclase enzymesꎬ DhLCYB and DhLCYE showed highly similar in protein 3D structure. (2)
                 DhLCYB and DhLCYE had different expression characteristics at different stages of flowering in Den ̄Phals. DhLCYE had
                 a higher expression level in yellow flowers than that in purple ̄red flowersꎬ and was significantly positively correlated with
                 the content of lutein and α ̄caroteneꎻ there was no regular pattern in the expression of DhLCYB in various cultivars with
                 different colorsꎬ but its expression level during the S1 stage was significantly positively correlated with the βꎬ β ̄
                 carotenoid metabolites of LCYB catalytic branching pathways such as antheraxanthin and violaxanthin. (3) A total of 48
                 kinds of carotenoids were identified from the flowers of Den ̄Phalsꎬ including 4 carotenes and 44 xanthophyllsꎻ the total
                 carotenoid content was higher in yellow cultivars than that in purple ̄red ones. (4) The content of 15 kinds of carotenoids
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                 and their derivativesꎬ as well as total carotenoidsꎬ was significantly negatively correlated with the chroma a value and
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                 significantly positively correlated with b value. This study provides genetic resources and breeding ideas for flower color
                 improvement of Den ̄Phals.
                 Key words: lycopene β ̄cyclaseꎬ lycopene ε ̄cyclaseꎬ gene cloningꎬ expression level analysisꎬ flower colorꎬ carotenoids


                类胡萝卜素( carotenoids) 是由异戊二烯骨架                   晨飞等ꎬ2022)ꎮ 2 个 GGPP 分子由八氢番茄红素
            构成的 C 或 C 萜类化合物ꎬ植物花、叶、根和果                          合酶(phytoene synthaseꎬPSY) 缩合产生 C 八氢番
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            皮等部位广泛存在类胡萝卜素( 戴思兰等ꎬ2013)ꎮ                         茄红素是类胡萝卜素生物合成途径中的第 1 个关
            类胡萝卜素种类与含量的不同ꎬ从而呈现出不同                              键步骤( 何静娟和范燕萍ꎬ2022)ꎮ 而番茄红素 β ̄
            程度的黄、橙、红等颜色( Kishimoto et al.ꎬ2004)ꎬ               环化酶( lycopene β ̄cyclaseꎬLCYB) 和番茄红素 ε ̄
            因其观赏性和营养价值ꎬ近年在园艺植物研究中                              环化酶( lycopene ε ̄cyclaseꎬLCYE) 是控制下游类
            备受关注(Hermanns et al.ꎬ 2020)ꎮ                       胡萝卜素合成分支的关键酶ꎮ
                 在类胡萝卜素生物合成途径中ꎬ类胡萝卜素                               在 LCYB 的催化下ꎬ番茄红素 2 个末端均形成
            最初来源于 2 个异戊二烯异构体ꎬ包括异戊二烯                            β 环ꎬ生成 β ̄胡萝卜素ꎮ 其在 β ̄胡萝卜素羟化酶
            焦磷酸( isopentenyl diphosphateꎬIPP) 和二甲基丙            (β ̄carotene hydrolaseꎬ BCH) 的催化下依次转变为
            烯基 二 磷 酸 ( dimethylallyl diphosphateꎬ DMAPP )ꎬ     β ̄隐 黄 质 ( β ̄cryptoxanthin ) 和 玉 米 黄 质
            其 主 要 通 过 甲 基 赤 藓 糖 磷 酸 ( 2 ̄C ̄methyl ̄D ̄            ( zeaxanthin )ꎮ 后 者 在 玉 米 黄 质 环 氧 化 酶
            erythritol 4 ̄phosphateꎬ MEP ) 途 径 合 成ꎮ 随 后ꎬ 在      (zeaxanthin epoxidaseꎬ ZEP) 的作用下依次合成花

            IPP 异构酶(isopentenyl diphosphate isomeraseꎬ IPI)    药黄质(antheraxanthin)和紫黄质( violaxanthin)ꎬ最
            和 牻 牛 儿 牻 牛 儿 基 焦 磷 酸 合 酶 ( geranylgeranyl         终 进 一 步 在 新 黄 质 合 酶 ( neoxanthin synthaseꎬ
            diphosphate synthaseꎬ GGPPS) 的 作 用 下ꎬ 1 分 子        NXS)的催化作用下生成新黄质(neoxanthin)ꎬ其可
            DMAPP 与 3 分子 IPP 缩合成 C 的牻牛儿牻牛儿                     作为合成脱落酸( abscisic acidꎬABA) 的前体物质
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            基焦磷酸( geranylgeranyl diphosphateꎬ GGPP) ( 陆        (Jahns & Holzwarthꎬ 2012ꎻNeuman et al.ꎬ 2014ꎻ刘
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