Aroma is a vital characteristic that determines the quality and commercial value of citrus fruits.Characteristic volatiles were analyzed in six different citrus species.In sweet orange,the sesquiterpene (+)-valencene is the characteristic 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 a regulator of (+)-valencene synthesis.The expression pattern of CitAP2.10 was positively correlated with (+)-valencene content and CsTPS1 expression.