Towards a molecular understanding of the biosynthesis of amaryllidaceae alkaloids in support of their expanding medical use.

The alkaloids characteristically produced by the subfamily Amaryllidoideae of the Amaryllidaceae, bulbous plant species that include well know genera such as Narcissus (daffodils) and Galanthus (snowdrops), are a source of new pharmaceutical compounds. Presently, only the Amaryllidaceae alkaloid galanthamine, an acetylcholinesterase inhibitor used to treat symptoms of Alzheimer's disease, is produced commercially as a drug from cultivated plants. However, several Amaryllidaceae alkaloids have shown great promise as anti-cancer drugs, but their further clinical development is restricted by their limited commercial availability.

Identification of key amino acids for the evolution of promoter target specificity of anthocyanin and proanthocyanidin regulating MYB factors.

A complex of R2R3-MYB and bHLH transcription factors, stabilized by WD40 repeat proteins, regulates gene transcription for plant cell pigmentation and epidermal cell morphology. It is the MYB component of this complex which specifies promoter target activation. The Arabidopsis MYB TT2 regulates proanthocyanidin (PA) biosynthesis by activating the expression of ANR (anthocyanidin reductase), the gene product of which catalyzes the first committed step of this pathway.

Why biosynthetic genes for chemical defense compounds cluster.

In plants, the genomic clustering of non-homologous genes for the biosynthesis of chemical defense compounds is an emerging theme. Gene clustering is also observed for polymorphic sexual traits under balancing selection, and examples in plants are self-incompatibility and floral dimorphy. The chemical defense pathways organized as gene clusters are self-contained biosynthetic modules under opposing selection pressures and adaptive polymorphisms, often the presence or absence of a functional pathway, are observed in nature.

Genomic clustering of cyanogenic glucoside biosynthetic genes aids their identification in Lotus japonicus and suggests the repeated evolution of this chemical defence pathway.

Cyanogenic glucosides are amino acid-derived defence compounds found in a large number of vascular plants. Their hydrolysis by specific β-glucosidases following tissue damage results in the release of hydrogen cyanide. The cyanogenesis deficient1 (cyd1) mutant of Lotus japonicus carries a partial deletion of the CYP79D3 gene, which encodes a cytochrome P450 enzyme that is responsible for the first step in cyanogenic glucoside biosynthesis.

The grapevine transcription factor VvMYBPA1 regulates proanthocyanidin synthesis during fruit development.

Proanthocyanidins (PAs; or condensed tannins) can protect plants against herbivores, contribute to the taste of many fruits, and act as dietary antioxidants beneficial for human health. We have previously shown that in grapevine (Vitis vinifera) PA synthesis involves both leucoanthocyanidin reductase (LAR) and anthocyanidin reductase (ANR). Here we report the characterization of a grapevine MYB transcription factor VvMYBPA1, which controls expression of PA pathway genes including both LAR and ANR.

Light-induced expression of a MYB gene regulates anthocyanin biosynthesis in red apples.

Anthocyanins are secondary metabolites found in higher plants that contribute to the colors of flowers and fruits. In apples (Malus domestica Borkh.), several steps of the anthocyanin pathway are coordinately regulated, suggesting control by common transcription factors.