Transcriptome analysis of a spontaneous reddish mutant in Miyagawa Wase Satsuma mandarin

Abstract

Color is one of the main characteristics determining the fruit quality of Citrus. A spontaneous mutant of Miyagawa Wase Satsuma mandarin (Citrus unshiu Marc.) was selected for its reddish coloration. At the start of ripening, color development of the mutant fruit was faster than that in wild-type fruit. At the mature stage, the intensity of red color in the peel was higher in the mutant without other changes in fruit characteristics. To understand the molecular basis of the mutant phenotype, microarray analysis was performed to observe genome-wide transcriptomic alterations in the mutant compared to the wild-type fruit. In the mutant, the expression levels of 582 genes were altered by more than 2-fold (p <0.05). Up-regulated genes were predominantly classified as genes involved in metabolism, cellular processing, and signaling. The expression levels of enzymes involved in carotenoid and flavonoid metabolisms, which are responsible for pigmentation in plants, were increased in the mutant, whereas enzymes involved in carotenoid degradation also were up-regulated. Confirming the microarray results, real-time reverse transcription-polymerase chain reaction data showed that expression of genes for carotenoid and flavonoid metabolism was strongly increased in the mutant. These results suggest that the changes of gene expression involved in carotenoid and/or flavonoid metabolism could responsible for the red-coloration in mutant.