Anthocyanin is a widely distributed flavonoid pigment that confers plant red color. The biosynthesis of anthocyanin associated with onset of color in developing plants has been well documented. However, whether anthocyanin biosynthesis pathway still functions in fruit at senescent stage remains unclear. In this study we investigated the metabolism of anthocyanin in litchi, a red fruit whose color fades fast after harvest. We showed as the pericarp browning index increased, the total anthocyanin contents decreased in litchi during storage at 20 °C. RNA-seq and proteomics analysis identified 4769 differentially expressed genes (DEG) and 84 differentially expressed proteins (DEP), respectively, in stored fruit compared with that before storage. Among them, 4 DEGs and 1 DEP involved in anthocyanin degradation, and 10 DEGs and 2 DEPs in anthocyanin biosynthesis pathway were upregulated. In particular, chalcone synthase (CHS), the first enzyme involved anthocyanin biosynthesis, and peroxidase (POD), a major enzyme for anthocyanin degradation, showed increased accumulation at both transcript and protein levels. LC-MS analysis showed that the accumulation of five anthocyanins and derivatives were decreased, while one anthocyanin increased in litchi stored for 6 d. These results suggest that anthocyanin degradation is accompanied by biosynthesis during pericarp browning, and that the browning of litchi resulted from more degradation than biosynthesis. The work provides new insight into mechanism underlying litchi browning during storage and possibilities for developing new browning prevention techniques. Additionally, from the evolutional perspective, this finding might imply that plants at senescent stage still try to preserve and disseminate the seeds against stresses.

花青素是一种广泛分布的类黄酮色素，赋予植物红色。花青素的生物合成与发育中植物的颜色开始有关，已被充分证明。然而，花青素生物合成途径在果实衰老阶段是否仍然发挥作用尚不清楚。在这项研究中，我们调查了荔枝中花青素的代谢，荔枝是一种在收获后颜色会迅速褪色的红色水果。我们发现，随着果皮褐变指数的增加，荔枝在 20°C 储存期间的总花青素含量下降。与储存前相比，RNA-seq 和蛋白质组学分析分别在储存水果中鉴定了 4769 个差异表达基因（DEG）和 84 个差异表达蛋白（DEP）。其中4个DEGs和1个DEP参与花青素降解，花青素生物合成途径中的10个DEGs和2个DEPs被上调。特别是查耳酮合酶 (CHS)，第一种涉及花青素生物合成的酶，以及过氧化物酶 (POD)，花青素降解的主要酶，在转录物和蛋白质水平上都显示出增加的积累。LC-MS分析表明，5种花青素及其衍生物的积累减少，而1种花青素在贮藏6 d的荔枝中增加。这些结果表明，在果皮褐变过程中，花青素的降解伴随着生物合成，荔枝褐变的原因是降解多于生物合成。这项工作为荔枝在储存过程中褐变的机制提供了新的见解，并为开发新的褐变预防技术提供了可能性。此外，从进化的角度来看，