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

System-Wide Expression and Function of Olfactory Receptors in Mammals

Olfactory receptors (ORs) in mammals are generally considered to function as chemosensors in the olfactory organs of animals. They are membrane proteins that traverse the cytoplasmic membrane seven times and work generally by coupling to heterotrimeric G protein. The OR is a G protein–coupled receptor that binds the guanine nucleotide-binding G(αolf) subunit and the Gβγ dimer to recognize a wide spectrum of organic compounds in accordance with its cognate ligand. Mammalian ORs were originally identified from the olfactory epithelium of rat. However, it has been recently reported that the expression of ORs is not limited to the olfactory organ. In recent decades, they have been found to be expressed in diverse organs or tissues and even tumors in mammals. In this review, the expression and expected function of olfactory receptors that exist throughout an organism's system are discussed.

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.