LcCDF3-LcTPS39 Regulatory Module Positively Regulates Caryophyllene Biosynthesis to Shape the Floral-Fruity Aroma of Litchi Aril.

Volatile terpenoids are pivotal to fruit aroma and serve as the major aroma-donating volatiles in litchi aril, yet their biosynthetic mechanisms remain largely unknown. By profiling 24 litchi cultivars, we identified 14 key terpenoids (e.g., caryophyllene, geraniol, and d-limonene) that classify cultivars into light and strong aroma groups. A genome-wide screening identified 46 LcTPS genes, with LcTPS39 showing the highest aril expression and functioning as a caryophyllene synthase. Transcriptomic and promoter analyses revealed a strong correlation between transcription factors LcCDF3 and LcTPS39. Subsequent in vitro and in vivo assays confirmed that LcCDF3 directly binds and activates the LcTPS39 promoter. Furthermore, overexpression of LcCDF3 in litchi callus and tomato fruits significantly enhanced caryophyllene production. Collectively, this study comprehensively characterizes litchi aril volatile terpenoids and elucidates a novel LcCDF3-LcTPS39 regulatory module controlling caryophyllene biosynthesis, offering valuable insights for the genetic improvement of fruit aroma.