Xi Liu

Huazhong Agricultural University, Wuhan, Hubei, China

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Publications (3)3.82 Total impact

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    ABSTRACT: Twelve watermelon [Citrullus vulgaris (Thunb.) Schrad (Cucurbitaceae)] cultivars with different flesh colors were analyzed by HPLC, GC-FID, and GC-MS for their differences in carotenoid, soluble sugar, organic acid, and flavor. Results showed that all-trans violaxanthin, 9-cis-violaxanthin, and luteoxanthin were the main carotenoid esters in watermelons with yellow flesh. However, watermelons with red flesh were rich in all-trans lycopene and their cis-isomers. High concentrations of β-carotene and pro-lycopenes were found in watermelon with orange-yellow flesh. Large variations in the sucrose concentration were observed among the different watermelons. Sucrose and/or fructose were the dominant sugars, while citric acid and malic acid were the main organic acids in watermelon flesh. Limonene was detected in the watermelon flesh of all investigated genotypes. Interestingly, partial correlation analysis of the chemical concentrations revealed 2 significant (p<0.01) positive correlations between β-ionone and β-carotene, and between (E)-geranyl acetone and prolycopenes.
    No preview · Article · Apr 2012 · Food science and biotechnology
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    ABSTRACT: Due to their theoretically identical genetic background, citrus callus and other plant tissues may share some mechanisms in the regulation of carotenogenesis. Thus, in order to gain further information on light regulation of carotenoids biosynthesis in citrus, the carotenoids and expression profiles of carotenogenesis in calluses of four citrus genotypes treated with light or dark were investigated. As a response to white light, results showed that carotenoids biosynthesis in callus of Red Marsh grapefruit (Citrus paradisi Macf.) was hampered, whereas callus of Tarocco blood orange (C. sinensis (L.) Osbeck) was sensitive to light by accumulating over 55% more carotenoids on average. Among the detected carotenoids, the biosynthesis of carotenes seemed to be more sensitive than that of xanthophylls. Expression profiles of eight carotenogenesis genes encoding phytoene synthase (PSY), phytoene desaturase (PDS), ζ-carotene desaturase (ZDS), carotenoids isomerase (CRTISO) etc. were investigated. Results revealed that PSY was up regulated in calluses of two sweet oranges, and down regulated in callus of Murcott tangor (C. reticulata × C. sinensis). Biochemical data in the three genotypes emphasized the PSY as a rate-limiting gene in the carotenogenesis. However, in the callus of Red Marsh grapefruit, PDS and ZDS might be the rate-limiting genes, and their transcripts were apparently inhibited by light, led to significant decreases in contents of β-carotene and total carotenoids irrelevant to transcription levels of PSY. Expression of CRTISO was light-induced, especially in the callus of Murcott tangor, and increased by nearly 12-fold. In conclusion, light regulates the expression of several carotenogenesis genes in citrus callus, but may not necessarily result in significant changes in carotenoids production.
    No preview · Article · Nov 2011 · Acta Physiologiae Plantarum
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    ABSTRACT: Eight carotenoids, such as phytoene, α-carotene, violaxanthin, etc., synthesized in citrus callus of 31 genotypes were identified and determined. Though varied with genotypes, the carotenoids composition of callus derived from a certain genotype was stable, while carotenoids contents altered between sub-cultures. Some specific carotenoids were produced in calluses of limited genotypes: β-citraurin was only synthesized in calluses of Nianju tangerine (Citrus reticulata Blanco) and Page tangelo (C. reticulata×C. paradisi); while 9-Z-violaxanthin was only detected in Nianju tangerine and Skaggs Bonanza navel orange (C. sinensis L. Osbeck). Notably, the only carotenoid detected in calluses of Natsudaidai (C. aurantium L.) and other two sweet oranges (C. sinensis L. Osbeck) was phytoene. It implied that citrus calluses could be employed to produce specific carotenoids in the future. To further elucidate the characters of callus carotenoids profile, comparisons of carotenoids profiles was made among calluses, fruit tissues and leaves of four selected citrus genotypes. Results showed that lycopene was not detected in leaves and calluses; nevertheless, both citrus fruits and calluses accumulated phytoene, whereas leaves did not except those of Cara Cara navel orange. It is postulated that citrus callus featured its carotenoids profile different from fruit tissues and leaves. In conclusion, the advantages of using citrus callus as an alternative model research system in understanding the regulation of carotenogenesis have been discussed. KeywordsCitrus callus–Carotenoids profile–Fruit tissues–Leaves
    No preview · Article · May 2011 · Acta Physiologiae Plantarum