Posttranscriptional Regulation of RhBRC1 (Rosa hybrida BRANCHED1) in Response to Sugars is Mediated via its Own 3' Untranslated Region, with a Potential Role of RhPUF4 (Pumilio RNA-Binding Protein Family).

Ming Wang,Laurence Hibrand Saint-Oyant,Philippe Grappin,Julien Jeauffre,Laurent Ogé,Soulaiman Sakr,Latifa Hamama,Maria-Dolores Perez-Garcia,Linda Voisine

doi:10.3390/ijms20153808

Abstract

The shoot branching pattern is a determining phenotypic trait throughout plant development. During shoot branching, BRANCHED1 (BRC1) plays a master regulator role in bud outgrowth, and its transcript levels are regulated by various exogenous and endogenous factors. RhBRC1 (the homologous gene of BRC1 in Rosa hybrida) is a main branching regulator whose posttranscriptional regulation in response to sugar was investigated through its 3′UTR. Transformed Rosa calluses containing a construction composed of the CaMV35S promoter, the green fluorescent protein (GFP) reporter gene, and the 3′UTR of RhBRC1 (P35S:GFP::3′UTRRhBRC1) 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 RhBRC1 in response to sugars, involving glycolysis/the tricarboxylic acid cycle (TCA) and the oxidative pentose phosphate pathway (OPPP). In Rosa vegetative buds, sequence analysis of the RhBRC1 3′UTR identified six binding motifs specific to the Pumilio/FBF RNA-binding protein family (PUF) and probably involved in posttranscriptional regulation. RhPUF4 was highly expressed in the buds of decapitated plants and in response to sugar availability in in-vitro-cultured buds. RhPUF4 was found to be close to AtPUM2, which encodes an Arabidopsis PUF protein. In addition, sugar-dependent upregulation of RhPUF4 was also found in Rosa calluses. RhPUF4 expression was especially dependent on the OPPP, supporting its role in OPPP-dependent posttranscriptional regulation of RhBRC1. These findings indicate that the 3′UTR sequence could be an important target in the molecular regulatory network of RhBRC1 and pave the way for investigating new aspects of RhBRC1 regulation.

Highlights

Throughout their life cycle, plants have to continually adjust to the various environmental conditions in which they are growing
Rosa calluses were transformed with a construction composed of the CaMV35S promoter, the green fluorescent protein (GFP) reporter gene upstream of the 3 UTR of RhBRC1 (P35S:GFP::3 UTRRhBRC1, Figure 1B)
We showed that one of the mechanisms behind the sucrose-dependent downregulation of RhBRC1 occurred through its 3′UTR sequence, which contains six putative PUF motifs, with one

Summary

Introduction

Throughout their life cycle, plants have to continually adjust to the various environmental conditions in which they are growing. Teosinte branched (TB1)/BRANCHED1 (BRC1) and its orthologous genes act as integrators of branching signals within axillary buds [6]. Teosinte branched (TB1) from Zea mays [8] and its respective homologs in Oryza sativa (OsTB1) [9] and in Sorghum bicolor (SbTB1) [10] were found to influence tillering. They encode transcription factors containing a TCP domain, a domain composed of around fifty-nine amino acids that allows for nuclear targeting, DNA binding, and protein–protein interactions [11,12,13]. BRC1-like genes have been identified in other plant species [5]

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