Journal Article

Biochemical and Genetic Analysis of Carbohydrate Accumulation in <i>Allium cepa</i> L

Shigenori Yaguchi, John McCallum, Martin Shaw, Meeghan Pither-Joyce, Shuichi Onodera, Norio Shiomi, Naoki Yamauchi and Masayoshi Shigyo

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 49, issue 5, pages 730-739
Published in print May 2008 | ISSN: 0032-0781
Published online May 2008 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcn048
Biochemical and Genetic Analysis of Carbohydrate Accumulation in Allium cepa L

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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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 ‘W202A× 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

Journal Article.  5347 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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