PLANT PHYSIOLOGY , Vol 113, Issue 3 773-778, Copyright © 1997 by American Society of Plant Biologists

DEVELOPMENT AND GROWTH REGULATION

Biosynthesis of GA73 Methyl Ester in Lygodium Ferns

T. Yamauchi, N. Oyama, H. Yamane, N. Murofushi, H. Schraudolf, M. Pour, H. Seto and L. N. Mander
Department of Applied Biological Chemistry (T.Y., N.O., N.M.) and Biotechnology Research Center (H.Y.), The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113, Japan

Biosynthesis of GA73 methyl ester (GA73-Me), the principal antheridiogen in Lygodium ferns, was investigated. From the methanol extract of prothallia of Lygodium circinnatum, GA25, GA73, GA73-Me, GA88-Me, and a few unknown GA73 derivatives were detected by GC-MS. Because the presence of GA25 suggests that GA24, a direct precursor of GA25, could also be present in L. circinnatum prothallia, we used feeding experiments to investigate the possibility that GA24 is a precursor of GA73-Me. In L. circinnatum prothallia, [2H2]GA24 was converted into [2H2]GA73-Me and a trace amount of [2H2]GA9-Me, whereas [2H3]GA9 was converted into [2H3]GA9-Me and [2H3]monohydroxy-GA9-Me. Because GA73-Me, GA9-Me, and their monohydroxy derivatives had been identified by GC-MS from the culture medium of L. circinnatum prothallia, our results suggest that GA73-Me is biosynthesized from GA24 via GA73, and that neither GA9 nor GA9-Me is a precursor of GA73-Me. Though the possibility had been suggested that GA73-Me is biosynthesized from 9,15-cyclo-GA9 (GA103), [2H2]GA103 was not converted into [2H2]GA73-Me.