Abstract

Summary en Capsaicinoids are a class of unique alkaloids that confer the pungent taste to pepper fruits. However, it remains largely unknown how light regulates the biosynthesis of capsaicinoids. We conducted a metabolic analysis on light- and dark-adapted pepper fruits. The results showed that dark-adapted pepper fruits had lower capsaicinoid contents and correspondingly downregulated transcription of capsaicinoid biosynthetic genes (CBGs), indicating that light plays a crucial role in capsaicinoid biosynthesis. Furthermore, silencing of CaHY5 , a pivotal transcription factor gene in the light signaling pathway, decreased the content of capsaicinoid and suppressed the expression of CBGs, whereas transient overexpression of CaHY5 generated exactly opposite results. CaHY5 can bind to the G-box motif in the promoters of CaBBX2 and CaACS8 , thereby enhancing their transcriptional levels. The activated CaBBX2 then binds to the T/G-box in the CaACS8 promoter to stimulate its expression. CaBBX2 or CaACS8 silencing led to decreased levels of capsaicinoids, while their transient overexpression produced increased capsaicinoid contents. Collectively, our results indicated that the light-activated CaHY5-CaBBX2-CaACS8 regulatory module plays a pivotal role in capsaicinoid biosynthesis. These findings provide new insights into the influence of light on capsaicinoid biosynthesis and potential targets for activation of this biosynthetic pathway in pepper. 概括 zh 辣椒素类物质是赋予辣椒果实独特辛辣风味的生物碱，然而光调控其合成的分子机制仍有待阐明。本研究对光照和黑暗处理的辣椒果实进行代谢组和转录组分析，发现黑暗处理显著降低辣椒素含量及辣椒素合成基因的转录水平，表明光在辣椒素生物合成中发挥关键作用。沉默 CaHY5 、 CaBBX2 或 CaACS8 均降低辣椒果实中的辣椒素含量，而它们的瞬时过表达则显著增加辣椒素含量。光信号通路核心转录因子CaHY5可结合 CaBBX2 和 CaACS8 启动子的G-box元件并促进其表达；被激活的CaBBX2可结合 CaACS8 启动子的T/G-box元件进一步增强其表达。综上所述，光激活的 CaHY5-CaBBX2-CaACS8 调控模块在辣椒素生物合成中发挥关键作用。本研究揭示了光调控辣椒素生物合成的新机制，并为激活辣椒 素合成通路提供了潜在靶点。