College of Horticulture and Landscape Architecture, Southwest University, Chongqing, 400716, People's Republic of China.
Laboratory of Fruit Quality Biology, Zhejiang University, Zijingang Campus, Hangzhou, 310058, People's Republic of China.
BMC Genomics. 2019 Nov 20;20(1):876. doi: 10.1186/s12864-019-6261-5.
Carotenoids are a class of terpenoid pigments that contribute to the color and nutritional value of many fruits. Their biosynthetic pathways have been well established in a number of plant species; however, many details of the regulatory mechanism controlling carotenoid metabolism remain to be elucidated. Apricot is one of the most carotenoid-rich fruits, making it a valuable system for investigating carotenoid metabolism. The purpose of this study was to identify key genes and regulators associated with carotenoid metabolism in apricot fruit based on transcriptome sequencing.
During fruit ripening in the apricot cultivar 'Luntaixiaobaixing' (LT), the total carotenoid content of the fruit decreased significantly, as did the levels of the carotenoids β-carotene, lutein and violaxanthin (p < 0.01). RNA sequencing (RNA-Seq) analysis of the fruit resulted in the identification of 44,754 unigenes and 6916 differentially expressed genes (DEGs) during ripening. Among these genes, 33,498 unigenes were annotated using public protein databases. Weighted gene coexpression network analysis (WGCNA) showed that two of the 13 identified modules ('blue' and 'turquoise') were highly correlated with carotenoid metabolism, and 33 structural genes from the carotenoid biosynthetic pathway were identified. Network visualization revealed 35 intramodular hub genes that putatively control carotenoid metabolism. The expression levels of these candidate genes were determined by quantitative real-time PCR analysis, which showed ripening-associated carotenoid accumulation. This analysis revealed that a range of genes (NCED1, CCD1/4, PIF3/4, HY5, ERF003/5/12, RAP2-12, AP2, AP2-like, BZR1, MADS14, NAC2/25, MYB1R1/44, GLK1/2 and WRKY6/31/69) potentially affect apricot carotenoid metabolism during ripening. Based on deciphering the molecular mechanism involved in ripening, a network model of carotenoid metabolism in apricot fruit was proposed.
Overall, our work provides new insights into the carotenoid metabolism of apricot and other species, which will facilitate future apricot functional studies and quality breeding through molecular design.
类胡萝卜素是一类萜烯类色素，为许多水果的颜色和营养价值做出贡献。其生物合成途径已在许多植物物种中得到很好的建立；然而，控制类胡萝卜素代谢的调控机制的许多细节仍有待阐明。杏是类胡萝卜素含量最丰富的水果之一，使其成为研究类胡萝卜素代谢的有价值系统。本研究旨在基于转录组测序鉴定与杏果实类胡萝卜素代谢相关的关键基因和调节剂。
在‘Luntaixiaobaixing’（LT）杏品种果实成熟过程中，总类胡萝卜素含量和β-胡萝卜素、叶黄素和玉米黄质的水平显著降低（p<0.01）。对果实进行 RNA 测序（RNA-Seq）分析，结果在成熟过程中鉴定出 44754 个 unigenes 和 6916 个差异表达基因（DEGs）。在这些基因中，33498 个 unigenes使用公共蛋白质数据库进行注释。加权基因共表达网络分析（WGCNA）显示，鉴定的 13 个模块中的两个（'蓝色'和'绿松石色'）与类胡萝卜素代谢高度相关，并且鉴定出 33 个类胡萝卜素生物合成途径的结构基因。网络可视化显示了 35 个潜在控制类胡萝卜素代谢的模块内枢纽基因。通过定量实时 PCR 分析确定这些候选基因的表达水平，该分析显示了与成熟相关的类胡萝卜素积累。该分析表明，一系列基因（NCED1、CCD1/4、PIF3/4、HY5、ERF003/5/12、RAP2-12、AP2、AP2-like、BZR1、MADS14、NAC2/25、MYB1R1/44、GLK1/2 和 WRKY6/31/69）可能影响杏果实成熟过程中的类胡萝卜素代谢。基于解析成熟过程中涉及的分子机制，提出了杏果实类胡萝卜素代谢的网络模型。
总体而言，我们的工作为杏和其他物种的类胡萝卜素代谢提供了新的见解，这将通过分子设计促进未来杏的功能研究和品质育种。
