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[Display omitted] • A tyrosine aminotransferase gene (RcTAT) was cloned from Rhodiola crenulata. • RcTAT catalyzes the formation of 4-hydroxyphenylpyruvate from tyrosine. • Suppression of RcTAT significantly enhances the salidroside production. Rhodiola crenulata is a traditional Tibetan medicinal plant mainly distributed in high altitude areas of Tibet. As the main extract of R. crenulata , salidroside has important medicinal activities in enhancing the body's immunity and resisting microwave radiation by influencing cell metabolism. Tyrosine is the starting amino acid precursor for salidroside biosynthesis. As an aromatic amino acid, tyrosine participates not only in salidroside biosynthesis, but also in other metabolite biosynthesis which might compete against salidroside biosynthetic pathway. In this study, we functionally identified a tyrosine aminotransferase in R. crenulata (RcTAT) that could convert tyrosine into 4-hydroxyphenylpyruvate (4-HPP). The Km and Vmax values of RcTAT for tyrosine were respectively 0.21 mM and 0.17 μmol/min.mg under 9.0 pH and 39 °C. RNAi-mediated suppression of RcTAT expression markedly increased salidroside production in hairy root culture of R. crenulata. In summary, RcTAT is a key gene involved in the metabolic pathway that competes against salidroside biosynthesis, and suppressing its expression is a promising way to elevate salidroside production in planta. [ABSTRACT FROM AUTHOR]

• Glyphosate is used for screening transgenic plants of Atropa belladonna. • Homozygous transgenic plants overexpressing HnH6H and G2-EPSPS are obtained. • Homozygous transgenic plants have high-yield scopolamine and glyphosate resistance. Atropa belladonna , one of the most important medicinal plants in China, is used to produce anticholinergic tropane alkaloids. Weeds severely reduce the agricultural productivity of A. belladonna in fields, and the low content of high-value scopolamine in planta limits its economic value. In this study, homozygous lines of A. belladonna , with glyphosate resistance and high yield of scopolamine, were developed using metabolic engineering technology for the first time. Two homozygous transgenic lines (T2GH03 and T2GH06), harboring G2-EPSPS and HnH6H , were established and tested in the field. Glyphosate resistance assays demonstrated that the two homozygous transgenic lines could resist commercial recommended dose of glyphosate. Alkaloid analysis showed that the transgenic lines produced more scopolamine than wild-type plants. T2GH03 and T2GH06 produced scopolamine at the levels of 5.45 mg/g dry weight (DW) and 7.04 mg/g DW respectively in leaves, and 1.06 mg/g DW to 1.07 mg/g DW respectively in roots. Compared with wild-type plants, the scopolamine contents of homozygous transgenic lines increased by over 10 folds in leaves and nearly 5 folds in roots. To sum up, Atropa belladonna's new varieties with glyphosate resistance and high-yield scopolamine are developed, which are highly valuable for industrial production of scopolamine. [ABSTRACT FROM AUTHOR]

• A root-expressed SAUR gene (AbSAUR1) was cloned from Atropa belladonna. • Overexpression of AbSAUR1 significantly increased the biomass of Atropa belladonna. • Overexpression of AbSAUR1 did not reduce biosynthesis of tropane alkaloids. • The yield of TAs was significantly improved in AbSAUR1 -overexpressing plants. Tropane alkaloids (TAs), including hyoscyamine, anisodamine and scopolamine, are widely used as anticholinergic drugs in the clinic. At present, the production of TAs is completely dependent on extraction from medicinal plants of Solanaceae. Atropa belladonna , commonly known as deadly nightshade, is a major commercial source of TAs. Previous studies have focused on increasing TA content by overexpressing TA biosynthesis genes. However, research on increasing TA yield by increasing the biomass of A. belladonna has not been reported. In this study, a Small Auxin Up-regulated RNA (SAUR) gene from A. belladonna (AbSAUR1) had been cloned for the first time. Based on heat map and tissue expression analysis, it was demonstrated that AbSAUR1 was specifically expressed in roots. Compared to control plants, transgenic lines of A. belladonna overexpressing AbSAUR1 showed a number of phenotypic changes, including increased plant height, thickened stems, increased number of branches, leaves and roots. Meanwhile, the biomass of AbSAUR1 -overexpressing plants also increased significantly, with fresh weight and dry weight being 3.79- and 3.20-fold higher than control plants, respectively. On average, there was no significant change in TA content, but the production of hyoscyamine, anisodamine and scopolamine was slightly enhanced. The overall yield of TAs was significantly improved, reaching 3.55 times that of the control. In summary, the AbSAUR1 gene can be employed as an effective molecular tool to increase the yield of TAs by increasing the biomass of A. belladonna. [ABSTRACT FROM AUTHOR]

AaPIF3, a bHLH transcription factor phylogenetically associated with Arabidopsis PIF3, positively regulates artemisinin biosynthesis in Artemisia annua. Overexpression of AaPIF3 significantly promotes the production of artemisinin and its related metabolites. • AaPIF3 is a bHLH transcription factor that is phylogenetically related with Arabidopsis PIF3. • AaPIF3 is able to transactivate artemisinin biosynthesis genes, according to dual-luciferase assays. • Overexpression of AaPIF3 markedly increased the production of artemisinin in Artemisia annua. Artemisia annua is a Chinese traditional herbal plant that produces artemisinin, the potent anti-malarial drug. It is a common goal for the artemisinin industry to develop plants of A. annua with high yields of artemisinin. In this study, a bHLH transcription factor of A. annua (AaPIF3) was characterized and used to promote the production of artemisinin. AaPIF3 was highly expressed in flower buds and glandular secretory trichomes and its coding protein was localized to the nucleus. Dual-luciferase assays indicated that AaPIF3 was able to significantly enhance the promoter activities of artemisinin biosynthesis genes, including ADS , CYP71AV1 , DBR2 , and ALDH1 , suggesting that AaPIF3 positively regulated artemisinin biosynthesis. Overexpression of AaPIF3 markedly upregulated artemisinin biosynthesis genes at the transcriptional level, and consequently the production of artemisinin was significantly promoted in transgenic A. annua plants. On the contrary, suppression of AaPIF3 led to significantly decreased transcript levels of artemisinin biosynthesis genes, with overall production of artemisinin significantly reduced. In summary, AaPIF3 plays a positive role in regulating artemisinin biosynthesis and transgenic plants of A. annua with high yields of artemisinin have been successfully developed through overexpression of AaPIF3. [ABSTRACT FROM AUTHOR]