Project description:BACKGROUND: Loropetalum chinense var. rubrum (L. chinense var. rubrum) is a precious, native, coloured-leaf ornamental plant in the Hunan Province. We found a L. chinense var. rubrum tree with 3 different leaf colours: GL (green leaf), ML (mosaic leaf) and PL (purple leaf). The mechanism of leaf coloration in this plant is still unclear. The aim of this study was to identify the metabolites and genes involved in determining the colour composition of L. chinense var. rubrum leaves, using phenotypic/anatomic observations, pigment content detection, and comparative metabolomics and transcriptomics.RESULTS: We observed that the mesophyll cells in PL were purple, those in GL were green and those in ML were a mix of purple-green. The contents of chlorophyll a, b, carotenoids and total chlorophyll in PL and ML were significantly lower than those in GL. While the anthocyanin content in PL and ML was significantly higher than that in GL. The metabolomics results showed that the differences in content of cyanidin 3-O-glucoside, delphinidin 3-O-glucoside, cyanidin 3,5-O-diglucoside, pelargonin and petunidin 3,5-diglucoside in ML, GL and PL were significant. Considering that the trend of anthocyanin content change was consistent with the leaf colour difference, we speculated that these compounds might influence the colour of L. chinense var. rubrum leaves. Finally, using transcriptomics, we identified 9 differentially expressed structural genes (one ANR (ANR1217); four CYP75A (CYP75A1815, CYP75A2846, CYP75A2909 and CYP75A1716); four UFGTs (UFGT1876, UFGT1649, UFGT1839 and UFGT3273) and nine transcription factors (two MYBs (MYB1057 and MYB1211), one MADS-box (MADS1235), two AP2-likes (AP2-like1779 and AP2-like2234), one bZIP (bZIP3720), two WD40s (WD2173 and WD1867) and one bHLH (bHLH1631) that might be related to flavonoid biosynthesis that impacted the appearance of colour in L. chinense var. rubrum leaves.CONCLUSIONS: This study revealed potential molecular mechanisms associated with leaf coloration in L. chinense var. rubrum by analysing differential metabolites and genes related to the anthocyanin biosynthesis pathway. It also provides a reference for research on leaf colour variation in other ornamental plants.

Project description:Radix bupleuri is a traditional Chinese crude drug and it is still widely used in contemporary medicine. Bupleurum chinense DC. and B. scorzonerifolium Willd. are officially recorded as the source species of Radix bupleuri in Pharmacopoeia of the PeopleM-bM-^@M-^Ys Republic of China. The obvious difference in chemical active components and pharmacological action of Radix bupleuri derived from the two species has caused attention. But to date, no definite criterions and regulates are issued based on plant species sources to direct the standard uses of Radix bupleuri for their extracts and traditional decoction pieces in medical market. Using 454-FLX pyrosequencing with one half-plate run for each cDNA library, a total of 419,576 and 416,112 reads, among those 313,483 and 342,263 high quality ESTs were obtained for B. chinense and B. scorzonerifolium, respectively. The average read length was 279 bp and 310 bp, respectively. The assembled 28,897 and 30,912 unigenes for B. chinense and B. scorzonerifolium were successively annotated based on sequence similarity by major public nucleotide/protein databases, Nt, Nr, SwissProt, KEGG, COG, Interpro and GO. Based on the alignments, 71.9% (20,787) and 75.8% (23,426) of the total unigenes for B. chinense and B. scorzonerifolium could be matched to nucleotides from NCBI Nt database. Certain percent from 27.1% (7,820) to 70.8% (20,461) of the total unigenes for B. chinense, and from 26.4% (8,145) to 72.1% (22,289) of the total unigenes for B. scorzonerifolium, could be matched to proteins from different databases. For the same database, similar percent of the total unigenes for B. chinense and B. scorzonerifolium were annotated. A total of 17,117 (59.2%) and 19,416 (62.8%) unigenes for B. chinense and B. scorzonerifolium could be found homologous genes in opposite dataset. According to KEGG annotation, 3,637 and 3,821 unigenes were assigned relating to metabolism in datasets of B. chinense and B. scorzonerifolium, respectively. Carbohydrate metabolism, energy metabolism and amino acid metabolism were the highest three groups in metabolism category and followed by lipid metabolism group for B. chinense. In comparison, lipid metabolism group had most unigenes for B. scorzonerifolium and it had much more unigenes than the same group for B. chinense (827 to 562). A total of 70 and 52 unigenes were related to metabolism of terpenoids and polyketides in two separate datasets, which seems agree with the situation of higher content of terpenoid saikosaponins in B. chinense than B. scorzonerifolium in some extent. To compare the biosynthesis of main bioactive components in roots of B. chinense and B. scorzonerifolium, putative genes which may participate in the biosynthesis of terpenoid, triterpenoid, sterol, ligan and flavonoid were searched according to unigenes annotation. Most lignan and flavonoid biosynthesis related genes were found in both datasets of B. chinense and B. scorzonerifolium, while some terpenoid or triterpenoid related genes were dominantly found in the dataset of B. chinense. This reflected in some extent that these genes expressed in low levels and relative metabolites were biosynthesized in lower quantities in roots of B. chinense than those of B. scorzonerifolium. Besides abovementioned comparison on two transcriptome, the expression of some genes involved in biosyntheses of main medicinal secondary metabolites were analyzed by qRT-PCR in roots of the two species. These molecular biological data will make a useful clue and arouse more studies on the reasonable application of the two Bupleurum species. The fine roots of two-year old plants of B. chinense and B. scorzonerifolium planted in the same place at the same time were collected at the usual harvest time of medicinal materials of Bupleurum. Those roots from the two species plants were used for 454 sequencing.

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