To investigate the gene expression characteristics and patterns of organic acid synthesis and accumulation in the pulp of Litchi chinensis Sonn. cv. Feizixiao (FZX), 16-year-old Feizixiao litchi trees were used as the experimental material, and the dynamic changes in the main organic acids in the pulp were determined for two years. RNA sequencing was carried out when the total acids in the pulp changed drastically 35, 50 and 73 d after anthesis in 2020 to discover the molecular mechanism of the synthesis and accumulation of different organic acids in pulp. The results indicate that tartaric acid and malic acid were the main organic acids in pulp. The RNA-seq contained 165,886 transcripts, and 12 176, 19 835 and 5 048 DEGs were observed in the 35 d vs. 50 d, 35 d vs. 73 d and 50 d vs. 73 d groups, respectively. These expressed transcripts of organic acid metabolism were significantly enriched in correlated pathways, including glycolysis and gluconeogenesis, citric acid cycle (TCA cycle), and ascorbate and aldarate metabolism. In this paper, 75 genes of the enzymes related to organic acid metabolic pathways were screened, and these enzymes included PEPC, MDH, ME, CS, IDH and ACO. Ten unigenes were selected to confirm by real-time PCR, and the linear regression between the RNA-Seq results and real-time PCR data was significant (r = 0.8637). In addition, the expression of PEPC and ACO genes was consistent with the content of citric acid, the expression of the CS gene increased with time, and the change in expression of the MDH gene was similar to that of the malic acid content, while the expression of the ME gene showed an opposite trend. Therefore, it was possible to regulate acid accumulation in pulp by regulating the expression of key genes related to pathways such as the TCA cycle, and then the comprehensive fruit quality was regulated.

研究荔枝果肉中有机酸合成积累的基因表达特征及模式松。简历。以飞子笑（FZX）16年生飞子笑荔枝树为试验材料，测定2年果肉中主要有机酸的动态变化。在2020年花后35、50和73 d果肉总酸发生剧烈变化时进行RNA测序，发现果肉中不同有机酸合成积累的分子机制。结果表明，酒石酸和苹果酸是纸浆中的主要有机酸。RNA-seq 包含 165,886 个转录本，在 35 天 vs. 50 天、35 天 vs. 73 天和 50 天 vs. 73 天组中分别观察到 12 176、19 835 和 5 048 个 DEG。这些有机酸代谢的表达转录物在相关途径中显着富集，包括糖酵解和糖异生，柠檬酸循环（TCA 循环），以及抗坏血酸和醛糖酸代谢。本文筛选了75个与有机酸代谢途径相关的酶基因，这些酶包括PEPC、MDH、ME、CS、IDH和ACO。选取 10 个 unigenes 进行实时 PCR 确认，RNA-Seq 结果与实时 PCR 数据之间的线性回归显着。r  = 0.8637）。此外，PEPC和ACO基因的表达与柠檬酸的含量一致，CS基因的表达随时间增加，MDH基因的表达变化与苹果酸含量的变化相似，而ME基因的表达呈现相反的趋势。因此，可以通过调控与TCA循环等途径相关的关键基因的表达来调控果肉中酸的积累，进而调控果实的综合品质。