Identification of source-sink tissues in the leaf of Chinese cabbage (Brassica rapa ssp. pekinensis) by carbohydrate content and transcriptomic analysis

• Published in: Genes & genomics Vol. 42; no. 1; pp. 13 - 24
• Main Authors: Lee, Jeongyeo, Dong, Xiangshu, Choi, Kwan, Song, Hayong, Yi, Hankuil, Hur, Yoonkang
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01.01.2020; Springer Nature B.V; 한국유전학회
• Subjects: Animal Genetics and Genomics; Biomedical and Life Sciences; biosynthesis; Brassica oleracea; Brassica rapa; Brassica rapa subsp. pekinensis; carbohydrate content; carbon; Chinese cabbage; Diurnal; DNA microarrays; Gene expression; gene ontology; genes; Genomes; Human Genetics; Leaves; Life Sciences; microarray technology; Microbial Genetics and Genomics; photosynthesis; Plant Genetics and Genomics; Post-transcription; quantitative polymerase chain reaction; Research Article; reverse transcriptase polymerase chain reaction; roots; Starch; Sucrose; tissues; transcription (genetics); transcriptomics; 생물학; Photosynthetic genes; Br300K microarray; Sugar transporters; Carbohydrate content; Large midrib
• ISSN: 1976-9571; 2092-9293; 2092-9293
• DOI: 10.1007/s13258-019-00873-z

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.