Brassinosteroids are inherently biosynthesized in the primary roots of maize, Zea mays L.
GC-MS analysis revealed that primary roots of maize contain 6-deoxocathasterone, 6-deoxoteasterone and 6-deoxotyphasterol. These brassinosteroids, and the previously identified campesterol, campestanol, 6-deoxocastasterone and castasterone, in the roots are members of a biosynthetic pathway to castasterone, namely the late C-6 oxidation pathway, suggesting that its biosynthetic pathway is operative in the roots. To verify this, a cell-free enzyme extract was prepared from maize roots, and enzymatic conversions from campesterol to castasterone through the aforementioned sterols and brassinosteroids were examined. The presence for the biosynthetic sequences, campesterol-->24-methylcholest-4-en-3beta-ol-->24-methylcholest-4-en-3-one-->24-methylcholest-5 alpha-cholestan-3-one-->campestanol and 6-deoxoteasterone-->6-deoxo-3-dehydroteasterone-->6-deoxotyphasterol-->6-deoxocastasterone-->castasterone were demonstrated. These results indicate that maize roots contain a complete set of enzymes involved in the late C-6 oxidation pathway, thereby demonstrating that endogenous brassinosteroids are biosynthesized in the roots.
Kim
Young-Soo
YS
Department of Life Science, Chung-Ang University, Seoul 156-756, Republic of Korea.
Kim
Tae-Wuk
TW
Kim
Seong-Ki
SK
D008956:Models, Chemical; D015394:Molecular Structure; D018517:Plant Roots / Q000201:enzymology / Q000378:metabolism*; D013256:Steroids / Q000096:biosynthesis*; D003313:Zea mays / Q000201:enzymology / Q000378:metabolism*
D013256:Steroids