Biosynthesis of ecdysteroids in in vitro prothalli cultures of Polypodium vulgare

• Published in: Phytochemistry (Oxford) 1996-10, Vol.43 (3), p.597-602
• Main Authors: Reixach, Natàlia, Irurre-Santilari, Josep, Casas, Josefina, Melé, Enric, Messeguer, Joaquima, Camps, Francisco
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Metabolism; Metabolism. Physicochemical requirements; Plant physiology and development
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/0031-9422(96)00336-6

The concentration of ecdysteroids in Polypodium vulgare has been studied in different parts of the wild plant as well as in the two in vitro micropropagated tissues. The ecdysteroid composition (abutasterone, polypodine B, 20-hydroxyecdysone, inokosterone, 24-hydroxyecdysone, pterosterone and ecdysone) was the same for all the sources investigated, but quantitative differences were found among them, with the exception of spores that did not produce these compounds. In contrast, the in vitro culture of spores originated the formation of haploid (prothalli) and diploid (sporophytes) tissues with a common feature: a proportion of 25-deoxyecdysone derivatives higher than that found in the wild plant. Prothalli micropropagated in vitro, generated from spores collected in different European areas, exhibited characteristic phytoecdysteroid contents that were constant over the four-year period studied. On the other hand, results on incorporation of radiolabelled ecdysteroid precursors, such as mevalonate, cholesterol or ecdysone, indicated that our in vitro system is adequate for biosynthetic studies. Labelled mevalonate and cholesterol were incorporated into all identified ecdysteroids, and labelled ecdysone was biotransformed into other 25-hydroxyecdysteroids present in this plant. Based on the different rates of incorporation of these precursors, a biosynthetic pathway for the last steps of ecdysteroid biosynthesis in P. vulgare was proposed.