Anthocyanins
Defensins
cDNA cloning, heterologous expressions, and functional characterization of malonyl-coenzyme a:anthocyanidin 3-o-glucoside-6"-o-malonyltransferase from dahlia flowers. (1/7)
In the flowers of important ornamental Compositae plants, anthocyanins generally carry malonyl group(s) at their 3-glucosyl moiety. In this study, for the first time to our knowledge, we have identified a cDNA coding for this 3-glucoside-specific malonyltransferase for anthocyanins, i.e. malonyl-coenzyme A:anthocyanidin 3-O-glucoside-6"-O-malonyltransferase, from dahlia (Dahlia variabilis) flowers. We isolated a full-length cDNA (Dv3MaT) on the basis of amino acid sequences specifically conserved among anthocyanin acyltransferases of the versatile plant acyltransferase family. Dv3MaT coded for a protein of 460 amino acids. Quantitative real-time PCR analyses of Dv3MaT showed that the transcript was present in accordance with the distribution of 3MaT activities and the anthocyanin accumulation pattern in the dahlia plant. The Dv3MaT cDNA was expressed in Escherichia coli, and the recombinant enzyme was purified to homogeneity and characterized. The recombinant Dv3MaT catalyzed the regiospecific transfer of the malonyl group from malonyl-coenzyme A (K(m), 18.8 microM) to pelargonidin 3-O-glucoside (K(m), 46.7 microM) to produce pelargonidin 3-O-6"-O-malonylglucoside with a k(cat) value of 7.3 s(-1). The other enzymatic profiles of the recombinant Dv3MaT were closely related to those of native anthocyanin malonyltransferase activity in the extracts of dahlia flowers. Dv3MaT cDNA was introduced into petunia (Petunia hybrida) plants whose red floral color is exclusively provided by cyanidin 3-O-glucoside and 3,5-O-diglucoside. Thirteen transgenic lines of petunia were found to produce malonylated products of these anthocyanins (11-63 mol % of total anthocyanins in the flower). The spectral stability of cyanidin 3-O-6"-O-malonylglucoside at the pHs of intracellular milieus of flowers was significantly higher than that of cyanidin 3-O-glucoside. Moreover, 6"-O-malonylation of cyanidin 3-O-glucoside effectively prevented the anthocyanin from attack of beta-glucosidase. These results suggest that malonylation should serve as a strategy for pigment stabilization in the flowers. (+info)Yellow flowers generated by expression of the aurone biosynthetic pathway. (2/7)
Flower color is most often conferred by colored flavonoid pigments. Aurone flavonoids confer a bright yellow color on flowers such as snapdragon (Antirrhinum majus) and dahlia (Dahlia variabilis). A. majus aureusidin synthase (AmAS1) was identified as the key enzyme that catalyzes aurone biosynthesis from chalcones, but transgenic flowers overexpressing AmAS1 gene failed to produce aurones. Here, we report that chalcone 4'-O-glucosyltransferase (4'CGT) is essential for aurone biosynthesis and yellow coloration in vivo. Coexpression of the Am4'CGT and AmAS1 genes was sufficient for the accumulation of aureusidin 6-O-glucoside in transgenic flowers (Torenia hybrida). Furthermore, their coexpression combined with down-regulation of anthocyanin biosynthesis by RNA interference (RNAi) resulted in yellow flowers. An Am4'CGT-GFP chimeric protein localized in the cytoplasm, whereas the AmAS1(N1-60)-RFP chimeric protein was localized to the vacuole. We therefore conclude that chalcones are 4'-O-glucosylated in the cytoplasm, their 4'-O-glucosides transported to the vacuole, and therein enzymatically converted to aurone 6-O-glucosides. This metabolic pathway is unique among the known examples of flavonoid, including anthocyanin biosynthesis because, for all other compounds, the carbon backbone is completed before transport to the vacuole. Our findings herein not only demonstrate the biochemical basis of aurone biosynthesis but also open the way to engineering yellow flowers for major ornamental species lacking this color variant. (+info)A new and distinct species in the genus Caulimovirus exists as an endogenous plant pararetroviral sequence in its host, Dahlia variabilis. (3/7)
(+info)Delta inulin: a novel, immunologically active, stable packing structure comprising beta-D-[2 -> 1] poly(fructo-furanosyl) alpha-D-glucose polymers. (4/7)
(+info)A bHLH transcription factor, DvIVS, is involved in regulation of anthocyanin synthesis in dahlia (Dahlia variabilis). (5/7)
(+info)'Le Rouge et le Noir': a decline in flavone formation correlates with the rare color of black dahlia (Dahlia variabilis hort.) flowers. (6/7)
(+info)Dahlia latent viroid: a recombinant new species of the family Pospiviroidae posing intriguing questions about its origin and classification. (7/7)
(+info)I apologize for any confusion, but "Dahlia" is not a medical term. It is the name of a genus of flowering plants belonging to the family Asteraceae. The Dahlia is the national flower of Mexico and comes in a variety of colors, sizes, and forms. If you have any medical questions or terms, I would be happy to help clarify those for you.
Anthocyanins are a type of plant pigment that belong to the flavonoid group. They are responsible for providing colors ranging from red, purple, and blue to black in various fruits, vegetables, flowers, and leaves. Anthocyanins have been studied extensively due to their potential health benefits, which include antioxidant, anti-inflammatory, and anti-cancer properties. They also play a role in protecting plants from environmental stressors such as UV radiation, pathogens, and extreme temperatures. Chemically, anthocyanins are water-soluble compounds that can form complex structures with other molecules, leading to variations in their color expression depending on pH levels.
Defensins are small, cationic host defense peptides that contribute to the innate immune system's response against microbial pathogens. They are produced by various cell types, including neutrophils, epithelial cells, and some bone marrow-derived cells. Defensins have a broad spectrum of antimicrobial activity against bacteria, fungi, viruses, and enveloped lipid bilayers.
Defensins are classified into two main groups: α-defensins and β-defensins. Human α-defensins include human neutrophil peptides (HNP) 1-4 and human defensin 5, 6 (HD5, HD6). These are primarily produced by neutrophils and Paneth cells in the small intestine. β-defensins, on the other hand, are produced by various epithelial cells throughout the body.
Defensins work by disrupting the microbial membrane's integrity, leading to cell lysis and death. They also have immunomodulatory functions, such as chemotaxis of immune cells, modulation of cytokine production, and enhancement of adaptive immune responses. Dysregulation of defensin expression has been implicated in several diseases, including inflammatory bowel disease, chronic obstructive pulmonary disease, and certain skin disorders.
Flavones are a type of flavonoid, which is a class of plant and fungal metabolites. They are characterized by a phenylbenzopyrone structure, consisting of two benzene rings (A and B) linked through a heterocyclic pyrone ring (C). Flavones specifically have a double bond between the second and third carbon atoms in the C ring, which contributes to their planar structure.
Flavones are found in various plants, including fruits, vegetables, and herbs, and they have been studied for their potential health benefits. Some common flavones include luteolin, apigenin, and chrysin. These compounds have been shown to have antioxidant, anti-inflammatory, and anticancer properties in laboratory studies, but more research is needed to determine their effectiveness and safety in humans.