title: Regulation of carotenoid accumulation and the expression of carotenoid metabolic genes in citrus juice sacs in vitro.
abstract: In the present study, to investigate the mechanisms regulating carotenoid accumulation in citrus, a culture system was set up in vitro with juice sacs of three citrus varieties, Satsuma mandarin (Citrus unshiu Marc.), Valencia orange (Citrus sinensis Osbeck), and Lisbon lemon (Citrus limon Burm.f.). The juice sacs of all the three varieties enlarged gradually with carotenoid accumulation. The changing patterns of carotenoid content and the expression of carotenoid metabolic genes in juice sacs in vitro were similar to those ripening on trees in the three varieties. Using this system, the changes in the carotenoid content and the expression of carotenoid metabolic genes in response to environmental stimuli were investigated. The results showed that carotenoid accumulation was induced by blue light treatment, but was not affected by red light treatment in the three varieties. Different regulation of CitPSY expression, which was up-regulated by blue light while unaffected by red light, led to different changes in carotenoid content in response to these two treatments in Satsuma mandarin and Valencia orange. In all three varieties, increases in carotenoid content were observed with sucrose and mannitol treatments. However, the accumulation of carotenoid in the two treatments was regulated by distinct mechanisms at the transcriptional level. With abscisic acid (ABA) treatment, the expression of the genes investigated in this study was up-regulated in Satsuma mandarin and Lisbon lemon, indicating that ABA induced its own biosynthesis at the transcriptional level. This feedback regulation of ABA led to decreases in carotenoid content. With gibberellin (GA) treatment, carotenoid content was significantly decreased in the three varieties. Changes in the expression of genes related to carotenoid metabolism varied among the three varieties in response to GA treatment. These results provided insights into improving carotenoid content and composition in citrus during fruit maturation.
authors: Department of Biological and Environmental Sciences, Faculty of Agriculture, Shizuoka University, 836 Ohya, Suruga, Shizuoka 422-8529, Japan.
authors: Lancui
authors: L
authors: Zhang
authors: Gang
authors: G
authors: Ma
authors: Masaya
authors: M
authors: Kato
authors: Kazuki
authors: K
authors: Yamawaki
authors: Toshihiko
authors: T
authors: Takagi
authors: Yoshikazu
authors: Y
authors: Kiriiwa
authors: Yoshinori
authors: Y
authors: Ikoma
authors: Hikaru
authors: H
authors: Matsumoto
authors: Terutaka
authors: T
authors: Yoshioka
authors: Hirohisa
authors: H
authors: Nesumi
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D001628:Beverages / Q000032:analysis; D002338:Carotenoids / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D002957:Citrus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D005638:Fruit / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D005875:Gibberellins / Q000378:metabolism; D008027:Light; D008353:Mannitol / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D013045:Species Specificity; D013395:Sucrose / Q000378:metabolism
chemical_list: D005875:Gibberellins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D002338:Carotenoids; D008353:Mannitol; D013395:Sucrose; D000040:Abscisic Acid