Dear Editor, Most of the plant hormones found in flowering plants contribute to growth regulation in the moss Physcomitrella patens.This moss does not produce gibberellin (GA) (Figure 1A).An entkaurene synthase (PpCPS/KS) and an ent-kaurene oxidase (PpKO) have been identified in P.patens,but in contrast to flowering plants,P.patens has no ent-kaurenoic acid oxidase (KAO) homologs (Hayashi et al.,2010;Miyazaki et al.,2011,Figure 1A).Nevertheless,several 2-oxoglutarate-dependent dioxygenase (2ODD) genes,which might be related to the GA synthesis pathway,have been annotated (Hirano et al.,2007),and ent-kaurene-deficient P.patens mutants (Ppcps/ks) showed limited protonemal cell differentiation of chloronemata to caulonemata,which are fast-growing cells that produce gametophores.The application of ent-kaurenoic acid (KA),but not GA,recovered the phenotype.These results support that P.patens lacks a GA biosynthetic pathway downstream of KA,indicating that KA metabolite(s) instead of GA may play physiological roles in P.patens.
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