|WEI, XU - Southwest University|
|YU, QIBIN - University Of Florida|
|GADY, ANTOINE - University Of Florida|
|YU, YUAN - University Of Florida|
|LIANG, GUOLO - Southwest University|
|GMITTER, FRED - University Of Florida|
Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2014
Publication Date: 7/1/2014
Publication URL: http://www.journals.elsevier.com/plant-science
Citation: Wei, X., Chen, C., Yu, Q., Gady, A., Yu, Y., Liang, G., Gmitter, F.J. 2014. Comparison of carotenoid accumulation and biosynthetic gene expression between Valencia and Rohde Red Valencia sweet oranges. Plant Science. 227(1):28–36.
Interpretive Summary: Diverse fruit colors are an important attribute for marketing appeal and healthy nutrition. One of the main coloration (pigmentation) sources is carotenoids, a group of pigments found in citrus, peach, carrot, pepper, and many other fruits and vegetables. Carotenoids vary among cultivars and species in compositions and levels, but little knowledge has been gained to understand the relation between the carotenoid color variability and the controlling and regulatory genes in their biosynthesis pathway. Quantification of the various pigments and biosynthetic gene expressions in maturing citrus fruits of two varieties with different flesh colors will be helpful to reveal the possible relation.
Technical Abstract: Carotenoid accumulation and biosynthetic gene expression levels during fruit maturation were compared between ordinary Valencia (VAL) and its more deeply colored mutant Rohde Red Valencia orange (RRV). The two cultivars exhibited different carotenoid profiles and regulatory mechanisms in flavedo and juice sacs, respectively. In flavedo, there was uncoordinated carotenoid accumulation and gene expression in RRV during green stages, which might be related to the expression of certain gene(s) in the MEP pathway. The carotenoid biosynthesis pathway shifting from a, ß-xanthophylls to ß, ß-xanthophylls synthesis occurred in RRV earlier than VAL during orange stages. In juice sacs, the low carotenoid content in both cultivars coincided with low expression of LCYE-Contig03 and LCYE-Contig24 during green stages, suggesting LCYE might be a limiting step for carotenoid accumulation. VAL mainly accumulated violaxanthin, but RRV accumulated ß-cryptoxanthin and violaxanthin during orange stages, which corresponded to differences in juice color. Several upstream genes (PDS-Contig17, LCYB-Contig19, and ZDS members) and a downstream gene (ZEP) were expressed at higher levels in RRV than VAL, which might be responsible for greater accumulation of ß-cryptoxanthin and violaxanthin in RRV, respectively.