|YU, QIBIN - University Of Florida|
|Baldwin, Elizabeth - Liz|
|HUANG, MING - University Of Florida|
|YU, YUAN - University Of Florida|
|DHALIWAL, HHARVINDER - University Of Florida|
|GMITTER, FREDERICK - University Of Florida|
Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2015
Publication Date: 3/6/2015
Citation: Yu, Q., Plotto, A., Baldwin, E.A., Bai, J., Huang, M., Yu, Y., Dhaliwal, H.S., Gmitter, F.G. 2015. Proteomic and metabolomic analyses provide insight into production of volatile and non-volatile flavor components in mandarin hybrid fruit. Biomed Central (BMC) Plant Biology. 15:76. doi:10.1186/s12870-015-0466-9.
Interpretive Summary: Citrus fruit and juice flavor consists of sugars, acids and aroma volatiles and color consists of carotenoids. The aroma and carotenoid components are the most complex and the synthesis and regulation of citrus carotenoids and aroma volatiles is little understood. Breeders selecting for flavor quality would benefit from an understanding of the regulation of these compounds. In citrus, the carotenoids and some terpenoid aroma volatiles share a biosynthetic pathway. In this study, two tangerine cultivars with differing color, carotenoid content and aroma volatile profiles were evaluated. The more intensely colored variety had more carotenoids, but no valencene, an aroma compound often found in citrus. This tangerine variety also had less of an enzyme that synthesizes this aroma compound. The other cultivar had less carotenoids (color) but more of the aroma compound, valencene and the enzyme that synthesizes valencene. This information will be useful to breeders in selecting for both color and flavor quality as there may be a trade-off between the two quality characteristics.
Technical Abstract: Although many of the volatile constituents of flavor and aroma in citrus have been identified, the molecular mechanism and regulation of volatile production is not well understood. Our aim was to understand mechanisms of flavor volatile production and regulation in mandarin fruit. To this end fruits from two mandarin cultivars of Temple and Murcott, which differ in volatile and non- volatile profiles, were collected at three different fruit development stages. A combination of methods, including in the isobaric tags for relative and absolute quantification (iTRAQ), quantitative real-time polymerase chain reaction (QPCR) and high-performance liquid chromatography (HPLC) was used to identify proteins, gene expression, volatiles, sugars, organic acids and carotenoids. Two thirds of the differentially expressed proteins were identified in the pathways of glycolysis, citric acid cycle, amino acid, sugar and starch metabolism. An enzyme encoded by the valencene synthase gene (Cstps1) was more abundant in Temple than Murcott. Valencene accounted for 9.4 % of total volatiles in Temple, whereas no valencene was detected in Murcott. We showed that the diversion of high valencene and other sesquiterpenes into the terpenoid pathway together with high apocarotenoid volatiles might have resulted in the lower concentration of carotenoids observed in mandarin.