BACKGROUND A leaf of Chinese cabbage (Brassica rapa ssp. pekinensis) is composed of a photosynthetic blade and a non-photosynthetic large midrib; thus each leaf contains both source and sink tissues. This structure suggests that, unlike in other plants, source-sink metabolism is present in a single leaf of Chinese cabbage. OBJECTIVE This study was designed to identify the transport route of photosynthetic carbon and to determine whether both source and sink tissues were present in a leaf. METHODS Plant samples were collected diurnally. Their carbohydrate contents were measured, and a genome-wide transcriptome analysis was performed using the Br300K microarray. Expression profiles of selected genes were validated using qRT-PCR analysis. RESULTS The presence of two contrasting tissues (blade as source and midrib as sink) in a leaf was demonstrated by (1) diurnal distribution patterns of starch and sucrose content; (2) Gene Ontology (GO) enrichment analysis of microarray data; (3) expression profiles of photosynthetic and sucrose biosynthetic genes; and (4) expression patterns of a variety of sugar transporter genes. CONCLUSION Source and sink tissues were both present in Chinese cabbage leaves, but the midrib functioned as a sink tissue as well as a site exporting to roots and other sink tissues. Function of most genes discriminating between source and sink tissue appeared to be regulated largely at the post-transcriptional level, not at the transcriptional level.

中文翻译：

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通过碳水化合物含量和转录组分析鉴定大白菜叶片中的源库组织。

背景技术大白菜（Brassica rapa ssp。pekinensis）的叶子由光合叶片和非光合大中脉组成。因此，每片叶子都包含源组织和汇聚组织。这种结构表明，与其他植物不同，大白菜的单叶中存在源库代谢。目的本研究旨在确定光合作用碳的运输途径，并确定叶片中是否同时存在源组织和宿组织。方法每天采集植物标本。测量了它们的碳水化合物含量，并使用Br300K微阵列进行了全基因组转录组分析。使用qRT-PCR分析验证所选基因的表达谱。结果叶片中存在两种相反的组织（叶片为来源，中脉为汇），其表现为（1）淀粉和蔗糖含量的昼夜分布模式；（2）基因本体（GO）对微阵列数据的富集分析；（3）光合和蔗糖生物合成基因的表达谱；（4）各种糖转运蛋白基因的表达模式。结论大白菜叶片均存在源组织和汇聚组织，但中脉既可以作为汇聚组织，也可以汇聚到根和其他汇聚组织。区分源组织和汇组织的大多数基因的功能似乎主要在转录后水平而不是转录水平受到调控。（2）基因本体（GO）对微阵列数据的富集分析；（3）光合和蔗糖生物合成基因的表达谱；（4）各种糖转运蛋白基因的表达模式。结论大白菜叶片均存在源组织和汇聚组织，但中脉既可以作为汇聚组织，也可以汇聚到根和其他汇聚组织。区分源组织和汇组织的大多数基因的功能似乎主要在转录后水平而不是转录水平受到调控。（2）基因本体（GO）对微阵列数据的富集分析；（3）光合和蔗糖生物合成基因的表达谱；（4）各种糖转运蛋白基因的表达模式。结论大白菜叶片均存在源组织和汇聚组织，但中脉既可以作为汇聚组织，也可以汇聚到根和其他汇聚组织。区分源组织和汇组织的大多数基因的功能似乎主要在转录后水平而不是转录水平受到调控。但是中肋既可以充当汇槽组织，也可以汇出到根部和其他汇水槽组织。区分源组织和汇组织的大多数基因的功能似乎主要在转录后水平而不是转录水平受到调控。但是中肋既可以充当汇槽组织，也可以汇出到根部和其他汇水槽组织。区分源组织和汇组织的大多数基因的功能似乎主要在转录后水平而不是转录水平受到调控。