title: Carotenoid accumulation affects redox status, starch metabolism, and flavonoid/anthocyanin accumulation in citrus.
abstract: BACKGROUND
  Carotenoids are indispensable plant secondary metabolites that are involved in photosynthesis, antioxidation, and phytohormone biosynthesis. Carotenoids are likely involved in other biological functions that have yet to be discovered. In this study, we integrated genomic, biochemical, and cellular studies to gain deep insight into carotenoid-related biological processes in citrus calli overexpressing CrtB (phytoene synthase from Pantoea agglomerans). Fortunella hindsii Swingle (a citrus relative) and Malus hupehensis (a wild apple) calli were also utilized as supporting systems to investigate the effect of altered carotenoid accumulation on carotenoid-related biological processes.
  
  
  RESULTS
  Transcriptomic analysis provided deep insight into the carotenoid-related biological processes of redox status, starch metabolism, and flavonoid/anthocyanin accumulation. By applying biochemical and cytological analyses, we determined that the altered redox status was associated with variations in O2 (-) and H2O2 levels. We also ascertained a decline in starch accumulation in carotenoid-rich calli. Furthermore, via an extensive cellular investigation of the newly constructed CrtB overexpressing Fortunella hindsii Swingle, we demonstrated that starch level reducation occurred in parallel with significant carotenoid accumulation. Moreover, studying anthocyanin-rich Malus hupehensis calli showed a negative effect of carotenoids on anthocyanin accumulation.
  
  
  CONCLUSIONS
  In citrus, altered carotenoid accumulation resulted in dramatic effects on metabolic processes involved in redox modification, starch degradation, and flavonoid/anthocyanin biosynthesis. These findings provided new perspectives to understand the biological importance of carotenogenesis and of the developmental processes associated with the nutritional and sensory qualities of agricultural products that accumulate carotenoids.
authors: Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, 430070, Wuhan, Hubei, China. yychb@mail.hebau.edu.|College of Horticulture, Agricultural University of Hebei, 071001, Baoding, Hebei, China. yychb@mail.hebau.edu.
authors: Hongbo
authors: H
authors: Cao
authors: Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, 430070, Wuhan, Hubei, China. wjbok@126.com.|Present address: College of Plant Science, Tarim University, 843300, Alar, China. wjbok@126.com.
authors: Jiangbo
authors: J
authors: Wang
authors: College of Horticulture, Agricultural University of Hebei, 071001, Baoding, Hebei, China. dreamslink002@163.com.
authors: Xintian
authors: X
authors: Dong
authors: College of Horticulture, Agricultural University of Hebei, 071001, Baoding, Hebei, China. hanyan5156340@126.com.
authors: Yan
authors: Y
authors: Han
authors: Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, 430070, Wuhan, Hubei, China. zizaishanren@163.com.
authors: Qiaoli
authors: Q
authors: Ma
authors: Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, 430070, Wuhan, Hubei, China. yuduanding@163.com.
authors: Yuduan
authors: Y
authors: Ding
authors: Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, 430070, Wuhan, Hubei, China. smifaye@sina.com.
authors: Fei
authors: F
authors: Zhao
authors: Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, 430070, Wuhan, Hubei, China. zjcnd001@163.com.|Present address: Shanxi Agricultural University, 030801, Taigu, Shanxi, China. zjcnd001@163.com.
authors: Jiancheng
authors: J
authors: Zhang
authors: College of Horticulture, Agricultural University of Hebei, 071001, Baoding, Hebei, China. chenhaijiang2001@163.com.
authors: Haijiang
authors: H
authors: Chen
authors: Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, 430070, Wuhan, Hubei, China. xuqiang@mail.hzau.edu.cn.
authors: Qiang
authors: Q
authors: Xu
authors: Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, 430070, Wuhan, Hubei, China. xujuan@mail.hzau.edu.cn.
authors: Juan
authors: J
authors: Xu
authors: Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, 430070, Wuhan, Hubei, China. xxdeng@mail.hzau.edu.cn.
authors: Xiuxin
authors: X
authors: Deng
mesh_terms: D000872:Anthocyanins / Q000096:biosynthesis*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002338:Carotenoids / Q000235:genetics / Q000378:metabolism*; D002957:Citrus / Q000737:chemistry* / Q000201:enzymology / Q000235:genetics / Q000648:ultrastructure; D005419:Flavonoids / Q000096:biosynthesis*; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase / Q000235:genetics / Q000378:metabolism; D027845:Malus / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D020636:Pantoea / Q000502:physiology; D027821:Rutaceae / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000648:ultrastructure; D017422:Sequence Analysis, DNA; D013213:Starch / Q000378:metabolism*
chemical_list: D000872:Anthocyanins; D001426:Bacterial Proteins; D005419:Flavonoids; D002338:Carotenoids; D013213:Starch; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase
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