Spice and Beverage Research Institute, Chinese Academy of Tropical Agricultural Sciences, Wanning, 571533, Hainan, China.
Key Laboratory of Genetic Resources Utilization of Spice and Beverage Crops, Ministry of Agriculture and Rural Affairs, Wanning, 571533, Hainan, China.
J Plant Res. 2021 Nov;134(6):1323-1334. doi: 10.1007/s10265-021-01338-9. Epub 2021 Aug 22.
The Theobroma cacao presents a wide diversity in pod color among different cultivars. Although flavonoid biosynthesis has been studied in many plants, molecular mechanisms governing the diversity of coloration in cacao pods are largely unknown. The flavonoid metabolite profiles and flavonoid biosynthetic gene expression in the pod exocarps of light green pod 'TAS 410' (GW), green pod 'TAS 166' (GF), and mauve pod 'TAS 168' (PF) were determined. Changes in flavonoid metabolites, particularly the anthocyanins (cyanidin 3-O-galactoside, cyanidin 3-O-glucoside, and cyanidin O-syringic acid) were significantly up-accumulated in the mauve phenotype (PF) compared to the light green or green phenotypes, endowing the pod color change from light green or green to mauve. Consistently, the PF phenotype showed different expression patterns of flavonoid biosynthetic structural genes in comparison with GW/GF phenotypes. The expression level of LAR and ANR in GW/GF was significantly higher than PF, while the expression level of UFGT in GW/GF was lower than PF. These genes likely generated more anthocyanins in the exocarps samples of PF than that of GW/GF. Simultaneously, colorless flavan-3-ols (catechin, epicatechin and proanthocyanidin) content in the exocarp samples of PF was lower than GW/GF. Additionally, MYB (gene18079) and bHLH (gene5045 and gene21575) may participate in the regulation of the pod color. This study sheds light on the molecular basis of cacao pod color variation, which will contribute to breeding cacao varieties with enhanced flavonoid profiles for nutritional applications.
可可豆荚在不同品种之间呈现出广泛的颜色多样性。尽管在许多植物中已经研究了类黄酮的生物合成，但可可豆荚颜色多样性的分子机制在很大程度上尚不清楚。本研究测定了浅绿荚 'TAS 410'（GW）、绿荚 'TAS 166'（GF）和淡紫色荚 'TAS 168'（PF）的外种皮中类黄酮代谢物谱和类黄酮生物合成基因表达。与浅绿或绿表型相比，淡紫色表型（PF）中类黄酮代谢物，特别是花色苷（矢车菊素 3-O-半乳糖苷、矢车菊素 3-O-葡萄糖苷和矢车菊素 O-丁香酸）显著增加，使荚色从浅绿或绿变为淡紫色。与 GW/GF 表型相比，PF 表型的类黄酮生物合成结构基因表达模式也不同。GW/GF 中 LAR 和 ANR 的表达水平明显高于 PF，而 GW/GF 中 UFGT 的表达水平低于 PF。这些基因可能在 PF 的外果皮样本中产生了比 GW/GF 更多的花色苷。同时，PF 外果皮样本中无色黄烷-3-醇（儿茶素、表儿茶素和原花青素）的含量低于 GW/GF。此外，MYB（基因 18079）和 bHLH（基因 5045 和基因 21575）可能参与了荚果颜色的调节。本研究揭示了可可豆荚颜色变化的分子基础，这将有助于培育具有增强类黄酮谱的可可品种，以用于营养应用。
