Abstract
Genetic studies have revealed that brassinosteroids (BRs) are essential plant hormones for growth and development of seed plants. However, little is known about the occurrence and physiological roles of BRs in ferns and moss. While the biosynthesis genes of sterols are highly conserved in the plant kingdom, down-stream genes responsible for BR biosynthesis are not likely to be present in the moss, Physcomitrella patens. Furthermore, no homolog of BRI1, a BR receptor, is found in the moss genome. In order to know whether P. patens produces BRs, we analyzed endogenous BRs using GC-MS. As the result, neither castasterone nor brassinolide that are biological active forms in seed plants were identified, but some of the precursors of these BRs such as 6-dexoxocastasterone were identified in P. patens. We discuss the biosynthesis of BRs in the moss in terms of presumptive BR biosynthesis genes.
