Characterization of Abscisic Acid and Ethylene in Regulating the White Blush in Fresh-Cut Carrots

The surface of fresh-cut carrots is apt to white blush, however the physiological and molecular mechanism for this process is not yet fully understood. In this study, exogenous abscisic acid (ABA) and ethylene separately promoted and inhibited the white-blush formation after three days after treatment, respectively. Metabolome analysis found that white-blush components mainly consist of p-hydroxyphenyl lignin and guaiacyl lignin. Transcriptome analysis found an increase in the whiteness values was consistent with the higher expression of genes encoding O-methyltransferase, trans-anol O-methyltransferase, bergaptol O-methyltransferase, caffeic acid 3-O-methyltransferase, phenylalanine ammonia-lyase, and ferulate-5-hydroxylase, together with the lower expression of genes encoding cinnamic acid 4-hydroxylase caffeoyl-CoA O-methyltransferase and 5-O-(4-coumaroyl)-D-quinate 3′-monooxygenase. In conclusion, ABA plays an important role in lignin biosynthesis essential to the formation of white blush in fresh-cut carrots. This is the first report that uncovers the physiological and molecular causes of white blush in fresh-cut carrots, providing a basis for white-blush control in fresh-cut carrots.