Mulberry (Morus alba L.) is used in traditional Chinese medicine and is the sole food source of the silkworm. Here, 21 cDNAs encoding phenylpropanoid biosynthetic genes and 21 cDNAs encoding triterpene biosynthetic genes were isolated from mulberry. The expression levels of genes involved in these biosynthetic pathways and the accumulation of rutin, betulin, and betulinic acid, important secondary metabolites, were investigated in different plant organs. Most phenylpropanoid and triterpene biosynthetic genes were highly expressed in leaves and/or fruit, and most genes were downregulated during fruit ripening. The accumulation of rutin was more than fivefold higher in leaves than in other organs, and higher levels of betulin and betulinic acid were found in roots and leaves than in fruit. By comparing the contents of these compounds with gene expression levels, we speculate that MaUGT78D1 and MaLUS play important regulatory roles in the rutin and betulin biosynthetic pathways.

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Rutin is an important indicator for evaluating the quality of buckwheat. In this study, flavonoid biosynthesis was compared between two common cultivars (an original and a high-rutin line) of buckwheat, Fagopyrum esculentum Moench. Transcriptional levels of the main flavonoid biosynthetic genes were analyzed by real-time PCR, and main flavonoid metabolites were detected by high-performance liquid chromatography (HPLC); levels of gene expression varied among organs of the two cultivars. Significantly higher transcription levels of most flavonoid biosynthetic genes, except FeFLS1, were detected in stems of the high-rutin line than in stems of the original line. FeCHI and FeFLS2 genes also showed higher expression levels in seeds of the high-rutin cultivar. In contrast, FePAL, FeC4H, Fe4CL1, FeCHS, FeF3H, FeF3'H, FeFLS2, and FeDFR were highly detected in the roots of the original line. The HPLC results indicated 1.73-, 1.62-, and 1.77-fold higher accumulation of rutin (the primary flavonoid compound) in leaves, stems, and mature seeds of the high-rutin cultivar (24.86, 1.46, and 1.36 μg/mg, respectively) compared with the original cultivar (14.40, 0.90, and 0.77 μg/mg, respectively). A total of 46 metabolites were identified from seeds by gas chromatography-time-of-flight mass spectrometry. The metabolite profiles were subjected to principal component analysis (PCA). PCA could clearly differentiate the original and high-rutin cultivars. Our results indicate that the high-rutin cultivar could be an excellent alternative for buckwheat culture, and we provide useful information for obtaining this cultivar.

BackgroundLycium chinense is well known in traditional Chinese herbal medicine for its medicinal value and composition, which have been widely studied for decades. However, further research on Lycium chinense is limited due to the lack of transcriptome and genomic information.ResultsThe transcriptome of L. chinense was constructed by using an Illumina HiSeq 2000 sequencing platform. All 56,526 unigenes with an average length of 611 nt and an N50 equaling 848 nt were generated from 58,192,350 total raw reads after filtering and assembly. Unigenes were assembled by BLAST similarity searches and annotated with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) orthology identifiers. Using these transcriptome data, the majority of genes that are associated with phenylpropanoid biosynthesis in L. chinense were identified. In addition, phenylpropanoid biosynthesis-related gene expression and compound content in different organs were analyzed. We found that most phenylpropanoid genes were highly expressed in the red fruits, leaves, and flowers. An important phenylpropanoid, chlorogenic acid, was also found to be extremely abundant in leaves.ConclusionsUsing Illumina sequencing technology, we have identified the function of novel homologous genes that regulate metabolic pathways in Lycium chinense.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-14-802) contains supplementary material, which is available to authorized users.

Zinc (Zn) is an essential micronutrient but in excess is highly toxic to plants. Plants regulate Zn homeostasis and withstand excess Zn through various pathways; these pathways are generally tightly regulated by a specific set of genes. However, the transcription factors involved in excess Zn tolerance have yet to be identified. Here, we characterized a Populus ussuriensis heat shock transcription factor A4a (PuHSFA4a) that acts as a positive regulator of excess Zn tolerance in P. ussuriensis. We used overexpression (PuHSFA4a-OE) and chimeric dominant repressor (PuHSFA4a-SRDX) lines to identify the targets of PuHSFA4a. PuHSFA4a transcription is specifically induced in roots by high Zn. Overexpression of PuHSFA4a conferred excess Zn tolerance and a dominant repressor version of PuHSFA4a increased excess Zn sensitivity in P. ussuriensis by regulating the antioxidant system in roots. PuHSFA4a coordinately activates genes related to abiotic stress responses and root development and directly binds to the promoter regions of glutathione-S-transferase U17 (PuGSTU17) and phospholipase A 2 (PuPLA 2). PuGSTU17 overexpression significantly increased GST activity and reduced reactive oxygen species levels in roots while PuGSTU17-RNA interference lines exhibited the opposite phenotype. Furthermore, PuPLA 2 overexpression promoted root growth under high Zn stress. Taken together, we provide evidence that PuHSFA4a coordinately activates the antioxidant system and root development-related genes and directly targets PuGSTU17 and PuPLA, thereby promoting excess Zn tolerance in P. ussuriensis roots.