ABSTRACT
The rol genes on pRiA4 plasmid of Agrobacterium rhizogenes are potent genes that promote secondary metabolism. Molecular breeding of Atropa belladonna can be conducted by introducing rol genes to increase tropane alkaloids (TAs) content in A. belladonna. In this study, the rolB gene was overexpressed in A. belladonna plants to study the effect of rolB gene on the biosynthesis of TAs. The phenotype, TAs content and expression levels of key enzyme genes in the pathway of TAs biosynthesis of transgenic A. belladonna were analyzed. The results showed that transgenic A. belladonna had developed root system, enlarged leaves, increased leaf fresh weight, deepened leaf color, enlarged flowers, changed flower shape, reduced pistil height and decreased pollen vitality. The content of TAs in the stems of transgenic A. belladonna was significantly higher than that of the control, and the contents of scopolamine, anisodamine, hyoscyamine can reach 2.11-2.91, 1.23-2.37 and 4.88-5.20 times of the control, respectively. Compared with the control group, the expressions of key enzymes putrescine N-methyltransferase (PMT), type III polyketide synthase (PYKS), tropinone reductase I (TRI), aromatic amino acid aminotransferase 4 (ArAT4), UDP-glycosyltransferase 1 (UGT1) and hyoscyamine 6-β-hydroxylase (H6H) in the TAs biosynthesis pathway were up-regulated, and the expression of tropinone reductase II (TRII) as a metabolic shunting gene was down-regulated. The results indicated that rolB gene enhanced TAs synthesis ability in roots and accumulation in stems of A. belladonna by enhancing metabolic flow of TAs synthesis pathway and weakening the metabolic shunt of competing pathway. This study laid a foundation for molecular breeding of A. belladonna with high-yield TAs content using rolB gene.
ABSTRACT
On the basis of the Uncaria transcriptome, specific primers were designed for UrSTR. The full-length cDNA of UrSTR (GeneBank: OL310251) was 1 541 bp, encoding 345 amino acid residues, and the promoter region sequence of UrSTR (GeneBank: OL310252) was 1 179 bp. Phylogenetic tree is revealed that UrSTR had a closest relationship with STR from Ophiorrhiza pumila and Ophiorrhiza japonica. Localization of UrSTR protein is revealed located in the vacuole membrane. Plant-care analysis indicated that the promoter region sequence of UrSTR, covering multiple light, stress and hormone-response cis-regulatory elements, and verified transcriptional activity. The results of SDS-PAGE show that pET-28a-UrSTR recombinant protein was successfully expressed, and the size was anticipated. The UrSTR prokaryotic expression system needs to be optimized in the later stage. The research lays the foundation for further purification to study its structure and functional characterization of the UrSTR protein.
ABSTRACT
Hair roots induced by Agrobacterium rhizogene produce higher levels of secondary metabolites than non-induced plants, and the enhanced metabolic capacity is driven by the rol gene. We hypothesized that rol genes can be utilized to improve the biosynthesis of tropane alkaloids (TAs) in Atropa belladonna. In this study, the rolC gene from Agrobacterium rhizogene pRiA4 plasmid, driven by a CaMV35S promoter, was overexpressed in A. belladonna. The phenotypes, TAs content and transcriptional expression of key genes in TAs biosynthesis were analyzed in transgenic A. belladonna plants. Results show that transgenic A. belladonna exhibited a well-developed root system, male sterility, higher stamen column length than pistil, early flowering, internode shortening, smaller but more flowers, increased axillary buds and lateral buds, decreased apical dominance, and long and narrow leaves as compared to wild-type plants. Transgenic A. belladonna produced more TAs than wild-type plants, with the content of hyoscyamine, anisodamine and scopolamine reaching 2.58, 3.59 and 15.77-fold that of the control group, respectively. The gene expression of putrescine N-methyltransferase (PMT), tropinone reductase I (TRⅠ) and hyoscyamine 6-β-hydroxylase (H6H), key enzymes in TAs biosynthesis, were up-regulated compared with the control group. The above results indicate that the rolC gene enhances TAs biosynthesis in A. belladonna by up-regulating the expression of key enzymes in the TAs biosynthesis pathway, laying a foundation for genetic manipulation of A. belladonna to increase TAs content by increasing rolC gene expression.