Wang Dan, Chen Lei, Yang Yabing, Abbas Farhat, Qin Yaqi, Lu Hanle, Lai Biao, Wu Zichen, Hu Bing, Qin Yonghua, Wang Huicong, Zhao Jietang, Hu Guibing
State Key Laboratory for Conservation and Utilization of Subtropical Agrobio-resources/Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (South China), Ministry of Agriculture and Rural Affairs/Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China.
School of Advanced Agriculture and Bioengineering, Yangtze Normal University, Fuling, China.
Physiol Plant. 2023 Jan;175(1):e13860. doi: 10.1111/ppl.13860.
Anthocyanins are health-promoting compounds with strong antioxidant properties that play important roles in disease prevention. Litchi chinensis Sonn. is a well-known and economically significant fruit due to its appealing appearance and nutritional value. The mature pericarp of litchi is rich in anthocyanins, whereas the aril (flesh) has an extremely low anthocyanin content. However, the mechanism of anthocyanin differential accumulation in litchi pericarp and aril remained unknown. Here, metabolome and transcriptome analysis were performed to unveil the cause of the deficiency of anthocyanin biosynthesis in litchi aril. Numerous anthocyanin biosynthesis-related metabolites and their derivatives were found in the aril, and the levels of rutin and (-)-epicatechin in the aril were comparable to those found in the pericarp, while anthocyanin levels were negligible. This suggests that the biosynthetic pathway from phenylalanine to cyanidin was present but that a block in cyanidin glycosylation could result in extremely low anthocyanin accumulation in the aril. Furthermore, 54 candidate genes were screened using weighted gene co-expression network analysis (WGCNA), and 9 genes (LcUFGT1, LcGST1, LcMYB1, LcSGR, LcCYP75B1, LcMATE, LcTPP, LcSWEET10, and LcERF61) might play a significant role in regulating anthocyanin biosynthesis. The dual-luciferase reporter (DLR) assay revealed that LcMYB1 strongly activated the promoters of LcUFGT1, LcGST4, and LcSWEET10. The results imply that LcMYB1 is the primary qualitative gene responsible for the deficiency of anthocyanin biosynthesis in litchi aril, which was confirmed by a transient transformation assay. Our findings shed light on the molecular mechanisms underlying tissue-specific anthocyanin accumulation and will help developing new red-fleshed litchi germplasm.
花青素是具有强大抗氧化特性的健康促进化合物，在疾病预防中发挥着重要作用。荔枝是一种因外观诱人且营养价值高而闻名且具有重要经济意义的水果。荔枝成熟的果皮富含花青素，而假种皮（果肉）中的花青素含量极低。然而，荔枝果皮和假种皮中花青素差异积累的机制尚不清楚。在此，进行了代谢组和转录组分析，以揭示荔枝假种皮中花青素生物合成不足的原因。在假种皮中发现了许多与花青素生物合成相关的代谢物及其衍生物，假种皮中芦丁和（-）-表儿茶素的水平与果皮中的相当，而花青素水平可忽略不计。这表明从苯丙氨酸到花青素的生物合成途径存在，但花青素糖基化的阻断可能导致假种皮中花青素积累极低。此外，使用加权基因共表达网络分析（WGCNA）筛选出54个候选基因，其中9个基因（LcUFGT1、LcGST1、LcMYB1、LcSGR、LcCYP75B1、LcMATE、LcTPP、LcSWEET10和LcERF61）可能在调节花青素生物合成中起重要作用。双荧光素酶报告基因（DLR）分析表明，LcMYB1强烈激活LcUFGT1、LcGST4和LcSWEET10的启动子。结果表明，LcMYB1是导致荔枝假种皮中花青素生物合成不足的主要定性基因，这通过瞬时转化试验得到证实。我们的研究结果揭示了组织特异性花青素积累的分子机制，并将有助于开发新的红肉荔枝种质。
