Uncovering tea-specific secondary metabolism using transcriptomic and metabolomic analyses in grafts of Camellia sinensis and C. oleifera
Camellia sinensis (L.) Kuntze and Camellia oleifera C. Abel (Theaceae) are closely related perennial woody shrubs, but the accumulation of metabolites and gene expression patterns are quite different between these two species. In order to understand the mechanisms behind the accumulation and biosynthesis of tea-specific secondary metabolites and the key genes that regulate their target pathways, 1-year-old clone cuttings of C. sinensis and C. oleifera were grafted in both directions, and self-grafted C. sinensis were used as controls. The transcriptomes and metabolomes of leaves and roots from the grafts were analyzed. We found that 1375 unigenes were up-regulated in the leaves of the CS-CO grafts (C. sinensis scion, C. oleifera stock), while 2437 unigenes were down-regulated. OPLS-DA models established for 7230 and 3223 mass spectra peaks were obtained in the positive and negative modes by LC-MS detection. Association analysis of the secondary metabolism pathways was performed, and the relative gene expressions of 14 genes from the transcriptome screening were verified by qRT-PCR. Among the differential metabolites screened and identified, we found that the relative levels of theanine and caffeine decreased significantly, and that many of the genes in these metabolic pathways were also down-regulated. In contrast, the levels of flavonoids apparently increased, and the expression of related genes in the flavonoid biosynthetic pathway were mostly up-regulated.
KeywordsCamellia sinensis C. oleifera Grafts Metabolome Transcriptome Secondary metabolism
This study was supported by the Natural Science Foundation of Anhui Province (Grant No.1608085QC60), the National Natural Science Foundation of China (NSFC) (Grant No. 31300576), the Changjiang Scholars and Innovative Research Team in University (Grant No. IRT_15R01), and Tea Plant Germplasm Resources Innovation Team Project of Fujian Academy of Agricultural Science (STIT2017-3-12). We appreciated Chun Liu (Beijing Genome Institute at Shenzhen, China) for technical support and analysis. We were also grateful to the elixigen editing service for the language polishing.
WD, JH, and YF prepared the material for sequencing and analyzed the data.YT, BZ, and ML participated in data analysis. WD, JH, YF, and RW were responsible for drafting and revising the manuscript. ZZ and XW guided this research.
Compliance with ethical standards
The authors declare that they complied with ethical standards.
The authors declare that they have no competing interests.
Data achieving statement
The clean data of grafts of Camellia sinensis and C. oleifera will be available in the NCBI SRA (http://www.ncbi.nlm.nih.gov/Traces/sra_sub/sub.cgi) under project accession number PRJNA429946 if the manuscript is accepted for publication in the tree genetics and genomes prior to publication.
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