摘要Brassinosteroids(BRs)are plant hormones that regulate wood formation in trees.Currently,little is known about the post-transcriptional regulation of BR synthesis.Here,we show that during wood formation,fine-tuning BR synthesis requires 3′UTR-dependent decay of Populus CONSTITUTIVE PHOTOMORPHOGENIC DWARF 1(PdCPD1).Overexpression of PdCPD1 or its 3′UTR fragment resulted in a significant increase of BR levels and inhibited secondary growth.In contrast,trans-genic poplars repressing PdCPD1 3′ UTR ex-pression displayed moderate levels of BR and promoted wood formation.We show that the Populus GLYCINE-RICH RNA-BINDING PROTEIN 1(PdGRP1)directly binds to a GU-rich element in 3′UTR of PdCPD1,leading to its mRNA decay.We thus provide a post-transcriptional mechanism underlying BRs synthesis during wood formation,which may be useful for genetic manipulation of wood biomass in trees.