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Aroma is a vital characteristic that determines the quality and commercial value of citrus fruits.Characteristic volatiles were analyzed in different citrus species.In sweet orange,the sesquiterpene(+)-valencene is a key volatile compound in fruit peel.Valencene synthesis is catalyzed by CsTPS1,but the transcriptional regulatory mechanisms controlling its gene expression are unknown.Here,one AP2/ERF transcription factor,CitAP2.10,is characterized as key regulator of(+)-valencene synthesis.The gene expression patterns of CitAP2.10 was positively correlated with(+)-valencene content and CsTPS1 activity.Dual-luciferase assays indicated that CitAP2.10 could trans-activate the CsTPS1 promoter.Ethylene enhanced expression of CitAP2.10 and this effect was abolished by the ethylene antagonist 1-MCP.The role and function of CitAP2.10 in(+)-valencene biosynthesis was confirmed using the Arabidopsis homolog(AtWRI1),as AtWRI1 also transiently activated the CsTPS1 promoter.Furthermore,transient overexpression of CitAP2.10 triggered(+)-valencene biosynthesis in sweet orange fruit.These results indicate that CitAP2.10 regulates(+)-valencene synthesis via induction of CsTPS1 mRNA accumulation.