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Título

Biotransformations of putative phytoecdysteroid biosynthetic precursors in tissue cultures of Polypodium vulgare

AutorReixach, Natàlia; Lafont, René; Camps Díez, Francisco; Casas Brugulat, Josefina
Palabras clave20-Hydroxyecdysone
Fern
Hydroxycholesterol derivatives
In vitro cultures
Induction
Fecha de publicacióndic-1999
EditorFederation of European Biochemical Societies
CitaciónFEBS Journal 266(2): 608-615 (1999)
ResumenIncubation of calli and prothalli of Polypodium vulgare with different tritium-labelled ecdysteroids has led to modification of some previous assumptions about the biosynthesis of ecdysteroids in plants. Thus, 25-deoxy-20-hydroxyecdysone was transformed efficiently in both tissues into 20-hydroxyecdysone (20E), but no 25-deoxyecdysteroids such as pterosterone and inokosterone were formed. Likewise, incubation of 2-deoxyecdysone (2dE) produced exclusively ecdysone (E) and 20E, indicating a high 2-hydroxylase activity in both tissues, despite calli not producing phytoecdysteroids. This 2-hydroxylation was also evident in the transformation of 2,22-dideoxyecdysone (2,22dE) into 22-deoxyecdysone (22dE). Different ecdysteroids that do not occur in P. vulgare were formed in the incubation of 3-dehydro-2,22,25-trideoxyecdysone (3D2,22,25dE) by 3α-reduction and 3β-reduction and 25-hydroxylation processes. The fact that 22,25-dideoxyecdysone and 22dE were the only 2-hydroxylated products formed in this case suggests that only compounds bearing a 3β-hydroxyl group are substrates for the 2-hydroxylase. Surprisingly, 22-hydroxylation was never observed with either 2,22dE or 3D2,22,25dE, raising the possibility that it could occur at an early step in the biosynthetic pathway. In this respect, labelled 22R-hydroxycholesterol was efficiently converted into E and 20E, whereas 22S-hydroxycholesterol was not transformed into ecdysteroids, because of its unsuitable configuration at C22. Finally, the conversion of 25-hydroxycholesterol into E and 20E was greatly enhanced after thermal treatment of prothalli which induces the release of previously stored ecdysteroids. Thus, P. vulgare prothalli and calli appear to be particularly suitable models for the study of ecdysteroid biosynthesis and its regulation in plants.
Descripción8 pages, 7 figures.-- PMID: 10561604 [PubMed].-- Available online Dec 25, 2001.
Versión del editorhttp://dx.doi.org/10.1046/j.1432-1327.1999.00905.x
URIhttp://hdl.handle.net/10261/26765
DOI10.1046/j.1432-1327.1999.00905.x
ISSN0014-2956 (Print)
1432-1033 (Online)
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