Proteomic and metabolomic analyses provide insight into production of volatile and non-volatile flavor components in mandarin hybrid fruit

Abstract

Background: Although many of the volatile constituents of flavor and aroma in citrus have been identified, the knowledge of molecular mechanisms and regulation of volatile production are very limited. Our aim was to understand mechanisms of flavor volatile production and regulation in mandarin fruit. Result: Fruits of two mandarin hybrids, Temple and Murcott with contrasting volatile and non-volatile profiles, were collected at three developmental stages. A combination of methods, including the isobaric tags for relative and absolute quantification (iTRAQ), quantitative real-time polymerase chain reaction, gas chromatography, and high-performance liquid chromatography, was used to identify proteins, measure gene expression levels, volatiles, sugars, organic acids and carotenoids. Two thirds of differentially expressed proteins were identified in the pathways of glycolysis, citric acid cycle, amino acid, sugar and starch metabolism. An enzyme encoding valencene synthase gene (Cstps1) was more abundant in Temple than in Murcott. Valencene accounted for 9.4% of total volatile content in Temple, whereas no valencene was detected in Murcott fruit. Murcott expression of Cstps1 is severely reduced. Conclusion: We showed that the diversion of valencene and other sesquiterpenes into the terpenoid pathway together with high production of apocarotenoid volatiles might have resulted in the lower concentration of carotenoids in Temple fruit.

Volatile and Nonvolatile Flavor Chemical Evaluation of USDA Orange–Mandarin Hybrids for Comparison to Sweet Orange and Mandarin Fruit

“…Yu et al (2015) observed that 'Murcott' and 'Temple' mandarin hybrids differed in valencene levels with the former producing little valencene, which agreed with the results in this research, and the latter producing substantial amounts of valencene. Valencene synthase (Cstps1) in the mevalonate pathway was found to be the key step in valencene production and was found differ in expression between 'Murcott' and 'Temple' hybrids (Yu et al, 2015). Other important terpene compounds included two terpene alcohols, linalool and terpinen-4-ol, and one terpene acetone, D-carvone (Table 2).…”

“…For orange juice (OJ) use, although sugars and acids are essential for good taste, it is the volatiles that in fact determine the unique flavor of a cultivar (Shaw, 1991). The hybrids between mandarin and sweet orange and their descendants generally show various fruit size, shape, color, and flavor features somewhere in between that of the parents (Hearn, 1989;Yu et al, 2015). When a hybrid possesses quality characteristics similar to sweet orange, there is a precedent that it might be officially classified and commercialized as ''sweet orange'' (Moshonas et al, 1991).…”

Changes in Volatile and Non-Volatile Flavor Chemicals of “Valencia” Orange Juice over the Harvest Seasons

“…The average detection frequency in this group was 68% in February, and continually increased to 72%, 82% and 91%, in following months, which follow the same trend as for the average peak sizes, although there were 16 compounds that were detected in all stages in this group (Figure 1). It is generally recognized that the sesquiterpene hydrocarbons are derived from acetyl-CoA through the mevalonic acid (MVA) pathway in the cytosol [53,54]. Valencene, the dominant sesquiterpene hydrocarbon, occurs in both peel oil (from oil glands in the flavedo) and juice oil (from oil bodies in the juice sacs).…”

The general and volatile properties and the quality of two newly selected Satsuma clones (11/1 İzmir and 30/ İzmir) grown under Mediterranean ecological conditions

“…According to the total sugar levels, the Dwari Satsuma sample had higher values than the 11/1 İzmir clone, and the 30/İzmir clone had the lowest total sugar level. Sucrose is known as the major sugar translocated in a plant, and it can be degraded by cell-wall sucrose synthase to glucose and fructose (Yu et al, 2015). The sucrose and the glucose levels were higher in the Dwari Satsuma sample than the 11/1 İzmir clone, and the 30/İzmir clone had the lowest level.…”

“…On particular, citric acid is the main organic acid in citrus fruit juice. Yun et al (2010) found that citric acid made up to 90% of the total organic acid content throughout the entire postharvest period (Yu et al, 2015). According to citric acid levels, the Dwari Satsuma sample is the least acidic sample followed by the 11/1 İzmir clone, whereas the 30/İzmir clone had the highest citric acid level.…”