Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Science, College of Horticulture, China Agricultural University, Beijing, 100193, China.
Theor Appl Genet. 2020 Sep;133(9):2729-2742. doi: 10.1007/s00122-020-03628-7. Epub 2020 Jun 20.
The anthocyanin biosynthesis gene Ca3GT was fine-mapped in a 110.5-kb region through a map-based cloning strategy. Gene expression and promoter analyses confirmed the strong candidate gene Capana10g001978. Pepper (Capsicum annum L.) fruit can be dark green, green, light green, purple, yellow, or ivory at the juvenile stage. Anthocyanins are responsible for fruit color formation in mature unripe pepper fruit, and transient accumulation of anthocyanins is the main problem in breeding pepper plants with mature purple fruit. Only a few genes controlling this trait have been cloned. The present study aimed to map and identify an anthocyanin biosynthesis gene from pepper using an F population derived from a cross between line '17C3808' (purple mature unripe fruit) and line '17C3807' (green mature unripe fruit). The trait was mapped on a 110.5-kb interval between markers SSR18213 and SSR18228 on chromosome 10. There were three open reading frames in this region; Capana10g001978 was predicted in this region as markers CAPS-78-708 and InDel146 co-segregated with it. Capana10g001978 is a structural gene encoding the GTB transcription factor involved in the biosynthesis of anthocyanins. Comparing parental sequences, two base mutations were identified in the exon of Capana10g001978, at positions + 528 bp and + 708 bp, which resulted in changes in the 176th and 236th amino acid residues, from glutamine (CAA) to histidine (CAC), causing a nonsense mutation (from CAG to CAA). Additionally, Capana10g001978 was highly expressed in the pericarp of mature, unripe pepper fruit. There were four single nucleotide polymorphisms, three sequence deletions, and one sequence insertion in the promoter region of purple, mature, and unripe pepper fruit, leading to the formation of a W-box and a GT1-motif. Thus, Capana10g001978 is a strong candidate gene of Ca3GT involved in anthocyanin biosynthesis in mature unripe pepper fruit. These results provide important information regarding the isolation and characterization of Ca3GT, and they are the starting point for studying the regulatory pathway responsible for anthocyanin biosynthesis in pepper.
花色苷生物合成基因 Ca3GT 通过图谱克隆策略精细定位在 110.5kb 区域内。基因表达和启动子分析证实了候选基因 Capana10g001978 的强候选性。辣椒（Capsicum annum L.）果实幼果期颜色为深绿、绿、浅绿、紫、黄或象牙色。花色苷负责成熟未成熟辣椒果实的颜色形成，花色苷的瞬时积累是培育成熟紫色果实辣椒植物的主要问题。只有少数控制该性状的基因被克隆。本研究旨在利用来自 '17C3808'（成熟未成熟紫色果实）和 '17C3807'（成熟未成熟绿色果实）杂交的 F 群体，从辣椒中定位和鉴定花色苷生物合成基因。该性状被定位在 10 号染色体 SSR18213 和 SSR18228 标记之间的 110.5kb 区间内。该区域有三个开放阅读框；Capana10g001978 被预测为该区域的标记 CAPS-78-708 和 InDel146 与其共分离。Capana10g001978 是一个结构基因，编码参与花色苷生物合成的 GTB 转录因子。比较亲本序列，在 Capana10g001978 的外显子中发现了两个碱基突变，位置分别在 +528bp 和 +708bp，导致第 176 位和第 236 位氨基酸残基的变化，从谷氨酰胺（CAA）变为组氨酸（CAC），导致无义突变（从 CAG 变为 CAA）。此外，Capana10g001978 在成熟未成熟辣椒果皮中高度表达。紫色、成熟未成熟辣椒果皮启动子区有四个单核苷酸多态性、三个序列缺失和一个序列插入，导致 W-box 和 GT1-motif 的形成。因此，Capana10g001978 是参与成熟未成熟辣椒果实花色苷生物合成的 Ca3GT 的强候选基因。这些结果为 Ca3GT 的分离和表征提供了重要信息，为研究辣椒花色苷生物合成的调控途径奠定了基础。
