Chalcone synthase
Encyclopedia
Chalcone synthases are a family of polyketide synthase
enzyme
s associated with the production of chalcones, a class of organic compound
s found mainly in plants as natural defense mechanisms and as synthetic intermediates, for example in the production of pigment
s. Although higher plant chalcone synthases have been extensively studied, little information is available on the enzymes from bryophytes (primitive plants). Cloning of CHS from the moss Physcomitrella patens
revealed an important transition from the chalcone synthases present in microorganisms to those present in higher plants.
The chalcone synthase gene
of Petunia
plants is famous for being the first gene in which the phenomenon of RNA interference
was observed; researchers intending to upregulate the production of pigments in light pink or violet flowers introduced a transgene
for chalcone synthase, expecting that both the native gene and the transgene would express the enzyme and result in a more deeply colored flower phenotype
. Instead the transgenic plants had mottled white flowers, indicating that the introduction of the transgene had downregulated or silenced chalcone synthase expression. Further investigation of the phenomenon indicated that the downregulation was due to post-transcriptional inhibition of the chalcone synthase gene expression
via an increased rate of messenger RNA
degradation.
Naringenin-chalcone synthase
uses malonyl-CoA
and 4-coumaroyl-CoA to produce CoA
, naringenin chalcone, and CO2.
Polyketide synthase
Polyketide synthases are a family of multi-domain enzymes or enzyme complexes that produce polyketides, a large class of secondary metabolites, in bacteria, fungi, plants, and a few animal lineages...
enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s associated with the production of chalcones, a class of organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
s found mainly in plants as natural defense mechanisms and as synthetic intermediates, for example in the production of pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
s. Although higher plant chalcone synthases have been extensively studied, little information is available on the enzymes from bryophytes (primitive plants). Cloning of CHS from the moss Physcomitrella patens
Physcomitrella patens
Physcomitrella patens is a moss used as a model organism for studies on plant evolution, development and physiology.-Model organism:...
revealed an important transition from the chalcone synthases present in microorganisms to those present in higher plants.
The chalcone synthase gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
of Petunia
Petunia
Petunia is a widely cultivated genus of flowering plants of South American origin, closely related with tobacco, cape gooseberries, tomatoes, deadly nightshades, potatoes and chili peppers; in the family Solanaceae. The popular flower derived its name from French, which took the word petun, meaning...
plants is famous for being the first gene in which the phenomenon of RNA interference
RNA interference
RNA interference is a process within living cells that moderates the activity of their genes. Historically, it was known by other names, including co-suppression, post transcriptional gene silencing , and quelling. Only after these apparently unrelated processes were fully understood did it become...
was observed; researchers intending to upregulate the production of pigments in light pink or violet flowers introduced a transgene
Transgene
A transgene is a gene or genetic material that has been transferred naturally or by any of a number of genetic engineering techniques from one organism to another....
for chalcone synthase, expecting that both the native gene and the transgene would express the enzyme and result in a more deeply colored flower phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
. Instead the transgenic plants had mottled white flowers, indicating that the introduction of the transgene had downregulated or silenced chalcone synthase expression. Further investigation of the phenomenon indicated that the downregulation was due to post-transcriptional inhibition of the chalcone synthase gene expression
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
via an increased rate of messenger RNA
Messenger RNA
Messenger RNA is a molecule of RNA encoding a chemical "blueprint" for a protein product. mRNA is transcribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes. Here, the nucleic acid polymer is translated into a polymer of amino acids: a protein...
degradation.
Naringenin-chalcone synthase
Naringenin-chalcone synthase
In enzymology, a naringenin-chalcone synthase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are malonyl-CoA and 4-coumaroyl-CoA, whereas its 3 products are CoA, naringenin chalcone, and CO2....
uses malonyl-CoA
Malonyl-CoA
Malonyl-CoA is a coenzyme A derivative.-Functions:It plays a key role in chain elongation in fatty acid biosynthesis and polyketide biosynthesis....
and 4-coumaroyl-CoA to produce CoA
Coenzyme A
Coenzyme A is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle. All sequenced genomes encode enzymes that use coenzyme A as a substrate, and around 4% of cellular enzymes use it as a substrate...
, naringenin chalcone, and CO2.