Largely different contents of terpenoids in beef red-flesh tangerine and its wild type

Abstract

BackgroundNiurouhong (Citrus reticulata Blanco. Niurouhong) (NRH) is a spontaneous beef-red flesh mutant with distinctive flavor compared with its wild type orange-red flesh Zhuhongju (ZHJ). To illustrate the biochemical mechanism of its special flesh color and flavor, fruits at commercial mature stage were used to profile the volatiles in the flavedo and determine the levels of carotenoids, limonoid aglycones and phytohormones in the juice sacs in two seasons.ResultsOur results showed the content of total volatile terpenoids in NRH was 1.27-fold that in ZHJ. The components of volatiles were found to be common between the two tangerines. This result indicates that the distinctive flavor of NRH might not be derived from the presence/absence of specific volatiles; instead, it was derived from the altered concentrations or balance of α-citral, β-citral, 2-cyclohexen-1-one, (S)-3-methyl-6-(1-methylethenyl) and n-hexadecanoic acid. Analyses of the contents of total and specific carotenoids indicated that the beef-red color of NRH flesh might be largely attributed to the over accumulation of β-cryptoxanthin and β-carotene. However, lower ABA level was found in NRH than in ZHJ, reflecting a possible feedback regulation of ABA biosynthesis on carotenogenesis and the balance in the metabolism among terpenoids.ConclusionsCollectively, our study suggested that the MEP pathway was enhanced in NRH tangerine. However, a certain unknown co-regulatory mechanism might be present in the metabolism pathway of secondary metabolites (especially terpenoids) in beef-red flesh mutant. Our study provides new insights into the regulatory network of terpenoid metabolism and mutation mechanism of red-fleshed citrus.

Volatile Compounds in Fruit Peels as Novel Biomarkers for the Identification of Four Citrus Species

“…There were abundant volatile compounds in citrus fruit. Lots of reports have mainly focused on the determination of volatile compounds and the comparison of the number and content of them in a few citrus germplasms [8,13,21,[24][25][26][27]. As different citrus species may have a unique aroma, the profiles of volatiles have been used to study citrus chemotaxonomy [8,24,25].…”

“…Both the composition and contents of volatile compounds are important in affecting the fruit odor and sensory properties. For instance, the contents of 16 volatile compounds were significantly changed in the fruit of Niurouhong (Citrus reticulata Blanco) in comparison with its wild type, Zhuhongju, resulting in significant changes in the aroma traits [13]. The contents of cisand trans-linalool oxides in Huanong Red pomelo fruit increased after being pollinated with Citrus mangshanensis, which consequently obtained the characteristic aroma of its pollen parent [14].…”

Transcriptomic and metabolomic analyses provide insight into the volatile compounds of citrus leaves and flowers

“…Thousands of metabolites in plants, such as flavonoids [1], carotenoids, limonoids, nomilins [2], furanocoumarins [3] and volatile terpenoids [4], have various functions with biological effects that are beneficial to humans [5]. The 2-C-methyl-D-erythritol-4-phosphate (MEP) and mevalonate (MVA) pathways in the plastids and cytoplasm of plants, respectively, synthesize C5 isopentenyl pyrophosphate (IPP) [5,6].…”

Putative Synergetic Genes Involved in the Syntheses of Carotenoids and Flavonoids in 'Cara cara' Navel Orange as Revealed by Integrated Transcriptome and Metabolomics Analysis

“…Citrus is one of the most important fruits in the world, and is rich in various primary and secondary metabolites, such as amino acids, organic acids, soluble sugars, avonoids, volatile terpenoids, limonoids, coumarins and carotenoids [1][2][3][4][5]. Some metabolites, including avonoids, limonoids, organic acids and soluble sugars, were reported to contribute to fruit taste [3,4], whilst terpenoids and carotenoids were associated with fruit aroma and color [2,6].…”