Posttranscriptional Regulation of () in Response to Sugars is Mediated via its Own 3' Untranslated Region, with a Potential Role of RhPUF4 (Pumilio RNA-Binding Protein Family).

The shoot branching pattern is a determining phenotypic trait throughout plant development. During shoot branching, () plays a master regulator role in bud outgrowth, and its transcript levels are regulated by various exogenous and endogenous factors. (the homologous gene of in ) is a main branching regulator whose posttranscriptional regulation in response to sugar was investigated through its 3'UTR. Transformed calluses containing a construction composed of the CaMV35S promoter, the green fluorescent protein (GFP) reporter gene, and the 3'UTR of (P35S:GFP::3'UTR) were obtained and treated with various combinations of sugars and with sugar metabolism effectors. The results showed a major role of the 3'UTR of in response to sugars, involving glycolysis/the tricarboxylic acid cycle (TCA) and the oxidative pentose phosphate pathway (OPPP). In vegetative buds, sequence analysis of the 3'UTR identified six binding motifs specific to the Pumilio/FBF RNA-binding protein family (PUF) and probably involved in posttranscriptional regulation. was highly expressed in the buds of decapitated plants and in response to sugar availability in in-vitro-cultured buds. was found to be close to , which encodes an PUF protein. In addition, sugar-dependent upregulation of was also found in calluses. expression was especially dependent on the OPPP, supporting its role in OPPP-dependent posttranscriptional regulation of . These findings indicate that the 3'UTR sequence could be an important target in the molecular regulatory network of and pave the way for investigating new aspects of regulation.