Effects of Salicylic Acid and Methyl Jasmonate Treatments on Flavonoid and Carotenoid Accumulation in the Juice Sacs of Satsuma Mandarin In Vitro  
[PERSON]  
1 Graduate School of Integrated Science and Technology, Department of Bioresource Sciences, Faculty of Agriculture, Shizuoka University, 836 Ohya, Suruga, Shizuoka 422-8529, Japan; [EMAIL_ADDRESS] (R.Y. ); [EMAIL_ADDRESS] (G.M. );[EMAIL_ADDRESS] (M.Y. ); [EMAIL_ADDRESS] (K.Y.) 2 Department of Bioresource Sciences, Faculty of Agriculture, Shizuoka University, 836 Ohya, Suruga, Shizuoka 422-8529, Japan; [EMAIL_ADDRESS] (L.Z. ); [EMAIL_ADDRESS] (M.H.) 3 National Institute of Fruit Tree Science (NIFTS), National Agriculture and Bio-Oriented Research Organization (NARO), Shizuoka, Shizuoka 424-0292, Japan; [EMAIL_ADDRESS] (T.S. ); [EMAIL_ADDRESS] (H.F.); [EMAIL_ADDRESS] (T.E.) * Correspondence: [EMAIL_ADDRESS]; Tel. : +81-54-238-4830  
Footnote †: These authors contributed equally: [PERSON] and [PERSON]. reported that dietary intake of \(\beta\)-cryptoxanthin reduced the risks of certain diseases, especially cancers, diabetes, and rheumatism, because of its antioxidant activity [3; 4; 5; 6; 7; 8]. In citrus fruit, flavonoids are also important secondary metabolites that tend to accumulate more in peel than in the pulp of the citrus fruit [9]. Flavonoids are a group of natural pigments with antifungal and anti-insect activities in plants and are thought to be involved in pathogen defense [10; 11]. In addition, flavonoids have been reported to have anticancer and anti-allergy activities in the human body [12; 13; 14]. In citrus fruit, the contents of flavonoids decreased gradually during the ripening process. To date, however, the molecular mechanism that regulates flavonoid accumulation and degradation is still unclear [11]. Salicylic acid and jasmonic acid are two important plant hormones involved in plant development and growth, and their roles in regulating carotenoid and flavonoid accumulation have been studied in different plant species. In previous studies, it was reported that salicylic acid treatment increased flavonoid content in tea and decreased carotenoid content in plum [15; 16]. In apple peel, it was found that methyl jasmonate treatment significantly promoted \(\beta\)-carotene accumulation [17]. In tomato, methyl jasmonate treatment promotes the lycopene accumulation through upregulating carotenoid biosynthetic pathway gene expression [18]. In citrus fruit, the research on the effects of salicylic acid and jasmonic acid is very limited. [PERSON] et al. reported that salicylic acid treatment induced flavonoid and carotenoid accumulation and further enhanced antioxidant activity of preharvest navel oranges [19]. To date, however, the roles of salicylic acid and jasmonic acid in regulating the carotenoid and flavonoid accumulation in the juice sacs are still far from being elucidated in citrus fruit. In the present study, to investigate how salicylic acid (SA) and methyl jasmonate (MeJA) treatments regulate flavonoid and carotenoid accumulation in the juice sacs of citrus fruit, we set up an in vitro system [20]. In the in vitro system, the juice sacs were cultured on MS medium supplemented with SA or MeJA, and the environmental conditions, such as light, water stress, and temperature were identical among the treatments. We evaluated the effects of plant hormones (abscisic acid and gibberellin), different colors of LED lights (blue and red), water stresses (sucrose and mannitol), and temperatures on carotenoid and ascorbate accumulation in the juice sacs of citrus fruit using this in vitro system [4; 20; 21; 22]. In the present study, to elucidate the regulation of carotenoid and flavonoid metabolisms in response to SA and MeJA treatments in citrus fruit, the effects of SA and MeJA on carotenoid and flavonoid accumulation and the expression of genes related to carotenoid and flavonoid biosynthesis were investigated in the juice sacs in vitro.