A gibberellin-stimulated ubiquitin-conjugating enzyme gene is involved in alpha-amylase gene expression in rice aleurone

A ubiquitin-conjugating enzyme (UBC) gene, induced by gibberellin (GA) within an hour, was identified in rice (Oryza sativa) seeds by the mRNA differential display technique. GA inducibility was confirmed by RNA hybridization. A full-length UBC cDNA clone and a genomic clone have been isolated and sequenced. The deduced amino acid sequence shares a significant identity with several known UBC sequences, which are probably involved in the pathway responsible for degrading short-lived regulatory proteins. In vivo transient assays using the UBC gene promoter, joined to the luciferase cDNA as the reporter gene, showed that the sequence located between positions 231 and 159 upstream of the transcription start site of this promoter is crucial for GA-dependent activation of the luciferase cDNA. Finally, trans-activation experiments indicated that this UBC gene is involved in gibberellin-stimulated a-amylase gene expression.