Plant and Cell Physiology Advance Access originally published online on March 27, 2008
Plant and Cell Physiology 2008 49(5):730-739; doi:10.1093/pcp/pcn048
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Biochemical and Genetic Analysis of Carbohydrate Accumulation in Allium cepa L
1Department of Biological and Environmental Sciences, Faculty of Agriculture, Yamaguchi University, Yamaguchi, 753-8515 Japan
2The United Graduated School of Agricultural Sciences, Tottori University, Tottori, 680-8553 Japan
3New Zealand Insitute for Crop and Food Research Limited, Private Bag 4704, Christchurch, New Zealand
4Department of Food Science, Faculty of Dairy Science, Rakuno Gakuen University, Ebetsu, Hokkaido, 069-8501 Japan
*Corresponding author: E-mail, shigyo{at}yamaguchi-u.ac.jp; Fax, +81-83-9335842.
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Abstract |
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Onion and shallot (Allium cepa L.) exhibit wide variation in bulb fructan content, and the Frc locus on chromosome 8 conditions much of this variation. To understand the biochemical basis of Frc, we conducted biochemical and genetic analyses of Allium fistulosum (FF)–shallot (A. cepa Aggregatum group) alien monosomic addition lines (AALs; FF+1A–FF+8A) and onion mapping populations. Sucrose and fructan levels in leaves of FF+2A were significantly lower than in FF throughout the year, and the springtime activity of acid invertase was also lower. FF+8A showed significantly higher winter sucrose accumulation and sucrose phosphate synthase (SPS) activity. Inbred high fructan (Frc_) lines from the ‘W202Ax Texas Grano 438’ onion population exhibited significantly higher sucrose levels prior to bulbing than low fructan (frcfrc) lines. Sucrose synthase (SuSy) activity in these lines was correlated with leaf hexose content but not with Frc phenotype. Markers for additional candidate genes for sucrose metabolism were obtained by cloning a major SPS expressed in onion leaf and exhaustively mining onion expressed sequence tag resources. SPS and SuSy loci were assigned to chromosome 8 and 6, respectively, using AALs and linkage mapping. Further loci were assigned, using AALs, to chromosomes 1 (sucrose phosphate phosphatase), 2 (SuSy and three invertases) and 8 (neutral invertase). The concordance between chromosome 8 localization of SPS and elevated leaf sucrose levels conditioned by high fructan alleles at the Frc locus in bulb onion or alien monosomic additions of chromosome 8 in A. fistulosum suggest that the Frc locus may condition variation in SPS activity.
Keywords: Fructan - Japanese bunching onion - Mapping - Onion - Sucrose
Abbreviations: AAL, monosomic alien addition line; DP, degree of polymerization; EST, expressed sequence tag; HPAEC, high-performance anion exchange chromatography; QTL, quantitative trait locus; RACE, rapid amplification of cDNA ends; RFLP, restriction fragment length polymorphism; RT–PCR, reverse transcription–PCR; SPS, sucrose phosphate synthase; 1-SST, sucrose:sucrose 1-fructosyltransferase; SuSy, sucrose synthase; UTR, untranslated region
5These authors contributed equally to this work.
(Received December 23, 2007; Accepted March 18, 2008)
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  S. Yaguchi, T. Nakajima, T. Sumi, N. Yamauchi, and M. Shigyo Profiling of Nondigestible Carbohydrate Products in a Complete Set of Alien Monosomic Addition Lines Explains Genetic Controls of Its Metabolisms in Allium cepa J. Amer. Soc. Hort. Sci., September 1, 2009; 134(5): 521 - 528. [Abstract] [Full Text] [PDF]
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