Swan Plant
The Swan Plant or Cotton Bush is an erect shrub to 2 m high producing a milky sap from all parts when damaged. The narrow leaves are opposite, 40-135 mm long, sparsely hairy, and pointed. The flowers are white to cream and arranged in small, often pendulous clusters in the leaf axils.
Swainsonine is a plant toxin found in lamb's quarters ( Chenopodium album ), arrowleaf dock ( Rumex hastatulus ), and prickly lettuce ( Lactuca serriola ). It is an irreversible inhibitor of glycosidases and has been extensively studied because of its similarity to the toxin alpha-mannosidosis in man.
Swainsonine has an unusual structure consisting of a single tricyclic ring system with amino sugars. The plant synthesizes Swainsonine from the amino sugars D-mannose and L-sorbose. The biosynthesis of Swainsonine begins with an NADPH-dependent reduction at C4 on protocatechuic acid to produce 4,4'-dihydroxybenzaldehyde (verbascoside). This compound then goes through a series of oxidations followed by complex rearrangements before the Swainsonine is produced.
Swainsonine is found in many members of the plant families Fabaceae, Scrophulariaceae, and Asclepiadaceae. It has been isolated from the leaves of several species including buffalo bur ( Solanum rostratum ) in the family Solanaceae and species of Asclepias and Cynanchum in the family Apocynaceae.
Swainsonine inhibits glycoprotein processing by specifically inhibiting N-linked mannosyl transferase activity. Inhibition of glycoprotein processing results from an irreversible attachment to a catalytic lysine residue. The inhibition occurs at the step of mannosyl transfer after the third mannose has been added to the protein. During glycoprotein processing, protein mannosyl transferase adds three mannoses sequentially to dolichol phosphate oligosaccharide protein.
Swainsonine is further metabolized in mammals to an alcohol-linked pentasaccharide, Swainsonine-β-D-glucopyranosyl-(1→2)-O-α-D-mannopyranosyl-(1→4)-D-glucopyranose. This β--linked pentasaccharide competes with the substrate for N--link mannosyl transferase and inhibits the addition of further mannoses.
Inhibition of glycoprotein processing results in a failure to transport newly synthesized proteins from the endoplasmic reticulum, which is a morphological consequence of the inhibition. The aberrant glycoproteins accumulate in the ER and disrupt its function because they cannot be transported out into the Golgi apparatus. There is an overall depression in glycoprotein processing at the level of the Golgi apparatus because of the failure to produce normal amounts of carbohydrate structures on proteins exiting from the cisternae. Proteins that are particularly sensitive to mannosylation are lysosomal enzymes and cell surface glycoproteins.
Global swan plant production
The swan plant is a native of Africa, and it is also found in parts of Asia and Australia. The plant grows in marshy areas and on the banks of rivers and lakes. It is a perennial plant that flowers from May to September. The flowers are white with yellow centers, and they are borne on long stalks that grow up to 2 meters in length. The plant has long, narrow leaves that are green on the top and white on the bottom. The swan plant is grown commercially for its flowers, which are used in bouquets and other floral arrangements. The plant is also grown as an ornamental plant. The swan plant is propagated by seed. It is a fast-growing plant, and it can become invasive in some areas. The swan plant is poisonous to humans and animals if ingested. The sap of the plant can cause skin irritation.
The swan plant is a native of Africa, and it is also found in parts of Asia and Australia. The plant grows in marshy areas and on the banks of rivers and lakes. It is a perennial plant that flowers from May to September. The flowers are white with yellow centers, and they are borne on long stalks that grow up to 2 meters in length. The plant has long, narrow leaves that are green on the top and white on the bottom. The swan plant is grown commercially for its flowers, which are used in bouquets and other floral arrangements. The plant is also grown as an ornamental plant. The swan plant is propagated by seed. It is a fast-growing plant, and it can become invasive in some areas. The swan plant is poisonous to humans and animals if ingested. The sap of the plant can cause skin irritation.