Journal Article

Gene Expression Activity and Pathway Selection for Sucrose Metabolism in Developing Storage Root of Sweet Potato

Xiu-Qing Li and Dapeng Zhang

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 6, pages 630-636
Published in print June 2003 | ISSN: 0032-0781
Published online June 2003 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcg080
Gene Expression Activity and Pathway Selection for Sucrose Metabolism in Developing Storage Root of Sweet Potato

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Development of sweet potato (Ipomoea batatas) storage root coincides with starch accumulation made using cleaved products of imported photoassimilate sucrose. The genes and pathways are predominantly active for sucrose metabolism in developing storage root were unknown. In this study, we used both an expressed sequence tag (EST) approach and a reverse transcription–polymerase chain reaction (RT-PCR) approach to answer this question. Sucrose synthase (SuSy) was found to be significantly more frequent in storage root ESTs than in fibrous root ESTs. SuSy was the most abundant carbohydrate-metabolism gene in the storage-root ESTs. RT-PCR results confirmed this by showing that invertase was active in fibrous roots but rapidly decreased to an undetectable level during storage root development while SuSy became predominant. Invertase expression was also detectable in young immature storage root and shoot tips, suggesting an involvement in cell formation. SuSy expression pattern showed considerable similarity to that of ADP-glucose pyrophosphorylase, an essential enzyme for starch synthesis. The results indicated that (i) SuSy was the most actively expressed enzyme in sucrose metabolism in developing storage root and was correlated with sink strength, and (ii) whereas invertase was active at cell formation stages, SuSy pathway was predominant for sucrose cleavage related to starch-accumulation.

Keywords: Keywords: Carbohydrate metabolism — Dry matter — Expressed sequence tags —Root development — Source-sink relationship — UDP-glucose pyrophosphorylase.; Abbreviations: AGPase, ADP-glucose pyrophosphorylase; CIP, International Potato Center; dNTP, deoxynucleoside triphosphate; EST, expressed sequence tag; RT-PCR, reverse transcription–polymerase chain reaction; SuSy, sucrose synthase; UGPase, UDP-glucose pyrophosphorylase.

Journal Article.  5176 words.  Illustrated.

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

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