Regulation of Ascorbic Acid Metabolism in Response to Different Temperatures in Citrus Juice Sacs in Vitro

To elucidate the regulation of ascorbic acid (AsA) metabolism in response to temperatures, three varieties of citrus juice sacs (Valencia orange, Lisbon lemon, and Satsuma mandarin) in in vitro culture system were subjected to different temperatures (10 degrees C, 20 degrees C, and 30 degrees C). The AsA accumulation was induced at 10 degrees C, whereas it was not significantly affected at 30 degrees C as compared with the control at 20 degrees C in juice sacs of the three citrus varieties. The enhancement of AsA accumulation at 10 degrees C was regulated by the expression of genes in AsA biosynthetic, oxidation, and regeneration pathway. In Valencia orange and Satsuma mandarin, the higher expression of CitVTC4 gene in biosynthetic pathway, and the higher expression of CitMDAR1 and CitMDAR2 genes in regeneration pathway, together with the lower expression of CitAO gene in oxidation pathway contributed to the higher AsA level at 10 degrees C. In Lisbon lemon, the higher expressions of CitVTC1, CitVTC2, and CitVTC4 genes in biosynthetic pathway and the lower expression of CitAO gene in oxidation pathway contributed to the higher AsA level at 10 degrees C. (C) 2017 Elsevier B.V. All rights reserved.