title: Transcriptome Analysis of Sucrose Metabolism during Bulb Swelling and Development in Onion (Allium cepaL.).
abstract: Allium cepaL. is a widely cultivated and economically significant vegetable crop worldwide, with beneficial dietary and health-related properties, but its sucrose metabolism is still poorly understood. To analyze sucrose metabolism during bulb swelling, and the development of sweet taste in onion, a global transcriptome profile of onion bulbs was undertaken at three different developmental stages, using RNA-seq. A total of 79,376 unigenes, with a mean length of 678 bp, was obtained. In total, 7% of annotated Clusters of Orthologous Groups (COG) were involved in carbohydrate transport and metabolism. In the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, "starch and sucrose metabolism" (147, 2.40%) constituted the primary metabolism pathway in the integrated library. The expression of sucrose transporter genes was greatest during the early-swelling stage, suggesting that sucrose transporters (SUTs) participated in sucrose metabolism mainly at an early stage of bulb development. A gene-expression analysis of the key enzymes of sucrose metabolism suggested that sucrose synthase, cell wall invertase, and invertase were all likely to participate in the hydrolysis of sucrose, generating glucose, and fructose. In addition, trehalose was hydrolyzed to two molecules of glucose by trehalase. From 15 to 40 days after swelling (DAS), both the glucose and fructose contents of bulbs increased, whereas the sucrose content decreased. The growth rate between 15 and 30 DAS was slower than that between 30 and 40 DAS, suggesting that the latter was a period of rapid expansion. The dataset generated by our transcriptome profiling will provide valuable information for further research.
authors.affiliation: Beijing Vegetable Research Center, Beijing Academy of Agriculture and Forestry Sciences/Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China) Beijing, China.
authors.forename: Chunsha
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Beijing Vegetable Research Center, Beijing Academy of Agriculture and Forestry Sciences/Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China) Beijing, China.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Zhang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Zongxiang
authors.initials: Z
authors.lastname: Zhan
authors.affiliation: Key Laboratory for Biology of Greenhouse Vegetable of Shandong Province, Institute of Vegetables and Flowers, Shandong Academy of Agricultural Sciences Jinan, China.
authors.forename: Bingjiang
authors.initials: B
authors.lastname: Liu
authors.affiliation: Vegetable Research Laboratory, Institute of Agricultural Sciences of Xuhuai Region in Jiangsu Lianyungang, China.
authors.forename: Zhentai
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Beijing Vegetable Research Center, Beijing Academy of Agriculture and Forestry Sciences/Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China) Beijing, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liang
keywords: Allium cepa L.; RNA-seq; bulb swelling; gene expression; sucrose metabolism