College of Horticulture, China Agricultural University, Beijing, 100193, China.
Department of Fruit Tree Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel.
BMC Plant Biol. 2023 Jul 15;23(1):361. doi: 10.1186/s12870-023-04368-8.
Red flesh is a desired fruit trait, but the regulation of red flesh formation in grape is not well understood. 'Mio Red' is a seedless table grape variety with light-red flesh and blue-purple skin. The skin color develops at veraison whereas the flesh color develops at a later stage of berry development. The flesh and skin flavonoid metabolomes and transcriptomes were analyzed.
A total of 161 flavonoids were identified, including 16 anthocyanins. A total of 66 flavonoids were found at significantly different levels in the flesh and skin (fold change ≥ 2 or ≤ 0.5, variable importance in projection (VIP) ≥ 1). The main anthocyanins in the flesh were pelargonidin and peonidin, and in the skin were peonidin, delphinidin, and petunidin. Transcriptome comparison revealed 57 differentially expressed structural genes of the flavonoid-metabolism pathway (logfold change ≥ 1, FDR < 0.05, FPKM ≥ 1). Two differentially expressed anthocyanin synthase (ANS) genes were annotated, ANS2 (Vitvi02g00435) with high expression in flesh and ANS1 (Vitvi11g00565) in skin, respectively. One dihydro flavonol 4-reductase (DFR, Vitvi18g00988) gene was differentially expressed although high in both skin and flesh. Screened and correlation analysis of 12 ERF, 9 MYB and 3 bHLH genes. The Y1H and dual luciferase assays showed that MYBA1 highly activates the ANS2 promoter in flesh and that ERFCBF6 was an inhibitory, EFR23 and bHLH93 may activate the DFR gene. These genes may be involved in the regulation of berry flesh color.
Our study revealed that anthocyanin biosynthesis in grape flesh is independent of that in the skin. Differentially expressed ANS, MYB and ERF transcription factors provide new clues for the future breeding of table grapes that will provide the health benefits as red wine.
红色果肉是人们所期望的果实特征，但葡萄中红色果肉形成的调控机制尚不清楚。‘Mio Red’是一种无核鲜食葡萄品种，其果肉呈浅红色，果皮呈蓝紫色。果皮颜色在转色期形成，而果肉颜色则在浆果发育的后期形成。对果肉和果皮的类黄酮代谢组学和转录组学进行了分析。
共鉴定出 161 种类黄酮，包括 16 种花色苷。果肉和果皮中差异表达的类黄酮有 66 种（差异倍数≥2 或≤0.5，变量重要性投影值（VIP）≥1）。果肉中的主要花色苷为矢车菊素和芍药素，果皮中的主要花色苷为芍药素、天竺葵素、飞燕草素和锦葵素。转录组比较显示，类黄酮代谢途径中有 57 个结构基因差异表达（差异倍数≥1，错误发现率（FDR）<0.05，每千碱基转录组每百万映射 reads（FPKM）≥1）。注释了 2 个差异表达的花色素苷合酶（ANS）基因，即 ANS2（Vitvi02g04355）在果肉中高表达，ANS1（Vitvi11g00565）在果皮中高表达。DFR（Vitvi18g00988）基因虽然在果皮和果肉中均高表达，但差异表达。筛选并分析了 12 个 ERF、9 个 MYB 和 3 个 bHLH 基因。Y1H 和双荧光素酶报告基因实验表明，MYBA1 可在果肉中高度激活 ANS2 启动子，而 ERFCBF6 为抑制因子，EFR23 和 bHLH93 可能激活 DFR 基因。这些基因可能参与了浆果果肉颜色的调控。
本研究表明，葡萄果肉中的花色苷合成与果皮中的花色苷合成是独立的。差异表达的 ANS、MYB 和 ERF 转录因子为未来培育具有红酒健康益处的鲜食葡萄提供了新的线索。
