Function analysis of anthocyanidin synthase from Morus alba L. by expression in bacteria and tobacco

Background: Flavonoids are a kind of important secondary metabolite and are commonly considered to provide protection to plants against stress and UV-B for a long time. Anthocyanidin synthase (ANS), which encodes a dioxygenase in the flavonoid pathway, catalyzes the conversion of leucoanthocyanidins to anthocyanidins, but there is no direct evidence indicating that it provides tolerance to stress in plants. Results: To investigate whether ANS can increase tolerance to abiotic stress, MaANS was isolated from mulberry fruits and transformed into tobacco. Our results suggested that the bacterially expressed MaANS protein can convert dihydroquercetin to quercetin. Overexpression of MaANS remarkably increased the accumulation of total flavonoids in transgenic lines and anthocyanins in corollas of flowers. Transgenic lines showed higher tolerance to NaCl and mannitol stress. Conclusions: These results indicated that MaANS participates in various dioxygenase activities, and it can protect plants against abiotic stress by improving the ROS-scavenging ability. Thus, this alternative approach in crop breeding can be considered in the improvement of stress tolerance by enriching flavonoid production in plants

Functional analysis of a chitinase gene PnCHI1 from Panax notoginseng / 中国中药杂志

Chitinases, a glycosidase enzyme that hydrolyzes chitin to N-acetylglucosamine, are widely found in plant cells, and they are an important part of plant antifungal defense system. The function of a Panax notoginseng chitinase gene PnCHI1 was characterized in this paper. Expression vector of PnCHI1 was constructed and transiently expressed in onion epidermal cells, and laser scanning confocal microscopy demonstrated that PnCHI1 was localized in the cell wall. Prokaryotic expression vector of PnCHI1 was also constructed, and recombinant protein of PnCHI1 was induced and purified. In vitro antibacterial assay showed that recombinant PnCHI1 protein had strong inhibitory activity on the mycelium growth of Fusarium solani, F. oxysporum and F. verticillioide. The function of PnCHI1 was further verified by reverse genetics. PnCHI1 expression vector was transferred into tobacco by Agrobacterium tumefaciens and expression of PnCHI1 was confirmed by qRT-PCR. It was found by leaf inoculation experiment that resistance of transgenic tobacco to F. solani was significantly increased. It is conclnded that: PnCHI1 is a chitinase localized in the cell wall, which inhibits several fungi which cause the root rot disease of P. notoginseng. Overexpression of this chitinase gene in tobacco greatly increased resistance to F. solani. PnCHI1 may be an important resistance gene in P. notoginseng that participates in the defense against root rot disease.

Cloning and ectopic expression analysis of squalene epoxidase 1 gene from Pseudostellaria heterophylla / 中草药

Objective: To clone the full-length cDNA encoding squalene epoxidase 1 (SQE1), a key enzyme of triterpenes biosynthesis, from Pseudostellaria heterophylla and to perform functional analysis. Methods: With the total RNA as template, the full-length cDNA of SQE1 in P. heterophylla was cloned via RT-PCR and rapid amplification of cDNA ends (RACE) techniques. The bioinformatics of the cloned SQE1 gene was performed. The target gene was transfered into tobacco by Agrobacterium-mediated transformation. Results: The full-length cDNA (2 038 bp) of SQE1 gene was obtained with an open reading frame of 1 554 bp, encoding 517 amino acid polypeptides, which had higher homology with the known SQEs in other medicinal species. The calculated relative molecular mass was 5.67 × 104, the isoelectric point was 8.8. The deduced protein sequence exhibited FAD-binding domains and four transmembrane regions. The content of total triterpenes was increased in transgenic tobacco plants. Conclusion: This is the first report that the full-length cDNA encoding SQE1 from P. heterophylla is cloned. The ectopic expression of SQE1 could promote to increase the content of total triterpenes in transgenic plant. This work provides a foundation for exploring the biosynthetic pathway of triterpenes in P.heterophylla and their applications in bioengineering.

Overexpression of HMGR and DXR from Amomum villosum Lour . Affects the Biosynthesis of Terpenoids in Tobacco / 世界科学技术-中医药现代化

HMGR and DXR are key enzymes of terpenoids biosynthesis pathway. This study was aimed to discuss the effects of overexpression of HMGR and DXR from A momum villosum Lour. on the biosynthesis of terpenoids in transgenic tobacco. The real-time fluorescence quantitative PCR (RT-qPCR) was used to analyze the expression level of AvHMGR and AvDXR. Then, enzyme activities of HMGR and DXR were determined by spectrometer using the substrate-specific method. Different terpenoids were detected by GC-MS. The results showed that individual overex-pression of HMGR/DXR can inhibit the enzyme activities of HMGR and DXR but promote the biosynthesis of men-thene, neophytediene, cembrenene and sterol. The co-overexpression of HMGR and DXR had different enzyme activ-ities and can promote the biosynthesis of sterol and phytol, but inhibit the biosynthesis of neophytadiene. It was con-cluded that the overexpression of HMGR and DXR had diverse effects when regulating the biosynthesis of different terpenoids. This study provided the basis for using A vHMGR and A vDXR to regulate the metabolism of terpenoids.

Isolation of choline monooxygenase (CMO) gene from Salicornia europaea and enhanced salt tolerance of transgenic tobacco with CMO genes.

Glycinebetaine (GB) is an osmoprotectant accumulated by certain plants in response to high salinity, drought, and cold stress. Plants synthesize GB via the pathway choline → betaine aldehyde → glycinebetaine, and the first step is catalyzed by choline monooxygenase (CMO). In the present study, by using RT-PCR and RLM-RACE, a full-length CMO cDNA (1844 bp) was cloned from a halophyte Salicornia europaea, which showed high homology to other known sequences. In order to identify its function, the ORF of CMO cDNA was inserted into binary vector PBI121 to construct the chimeric plant expression vector PBI121-CMO. Using Agrobacterium (LBA4404) mediation, the recombinant plasmid was transferred into tobacco (Nicotiana tabacum). The PCR, Southern blot and RT-PCR analysis indicated the CMO gene was integrated into the tobacco genome, as well as expressed on the level of transcription. The transgenic tobacco plants were able to survive on MS medium containing 300 mmol/L NaCl and more vigorous than those of wild type with the same concentration salt treatment. In salt-stress conditions, transgenic plants had distinctly higher chlorophyll content and betaine accumulation than that of the control, while relative electrical conductivity of transgenic plants was generally lower. The results suggested the CMO gene transformation could effectively contribute to improving tobacco salt-resistance.

Transgenic Tobacco Expressing the Crocus CSzCD Gene Showed the Production of Crocetin / 中国生物工程杂志

To investigate the feasibility to produce crocetin in tobacco plants.The coding region of zeaxanthin cleavage dioxygenase (CSzCD) gene from Crocus sativus L. was inserted into the downstream of the cauliflower mosaic virus (CaMV) 35S promoter of a binary vector pBI121, and integrated into the genome of Nicotiana tabacum L. Twenty-one transgenic lines were identified by genomic southern blotting analysis. Western blotting and HPLC analysis of the leaf extracts of transgenic tobacco showed that crocetin was produced in CSzCD gene-transformed plants, while no crocetin was found in the untransformed tobacco.

Expression of a Kind of Curcin Induced from Jatropha curcas (curicin 2) in Tobacco / 中国生物工程杂志

A new kind of curcin (curcin 2), induced by several kinds of stresses from Jatropha curcas leaves, under the control of the 35S CaMV (cauliflower mosaic virus) promoter, was introduced into tobacco genome by Agrobacterium tumefaciens-mediated transformation method. Curcin 2 protein was only detected in the transgenic tobacco plants transformed with the cur2p fragment (coding premature curcin 2 protein), but not in the plants transformed with cur2m fragment (coding mature curcin 2 protein). The transgenic lines expressing curcin 2 showed increased tolerance to tobacco mosaic virus (TMV).