Roots and shoots of tomato produce 6-deoxo-28-norcathasterone, 6-deoxo-28-nortyphasterol and 6-deoxo-28-norcastasterone, possible precursors of 28-norcastasterone

Roots and shoots of tomato (Lycopersicon esculentum) were investigated for the occurrence of biosynthetic precursors of 28-norcastasterone, a C-27 bra ssinosteroid that we have shown to be present in shoots of tomato. A series of putative precursors, including 6-deoxo-28-norcathasterone, 6-deoxo-28-n orteasterone, 3-dehydro-6-deoxo-28-norteasterone, 6-deoxo-28-nortyphasterol and 6-deoxo-28-norcastasterone, were synthesized and used as GC-MS standar ds, resulting in the identification of 6-deoxo-28-norcathasterone, 6-deoxo- 28-nortyphasterol and 6-deoxo-28-norcastasterone in both roots and shoots. These findings indicate that the biosynthesis of 28-norcastasterone may par allel that of castasterone. The endogenous levels of brassinosteroids diffe red between roots and shoots, indicating that the biosynthesis of brassinos teroids is differently regulated between these tissues. Regulation of root growth by brassinosteroids is also discussed. (C) 2001 Elsevier Science Ltd . All rights reserved.