BRANCHED1 Interacts with FLOWERING LOCUS T to Repress the Floral Transition of the Axillary Meristems inArabidopsis

Masaki Niwa,Motomu Endo,Yasufumi Daimon,Nobutaka Mitsuda,Masaru Ohme-Takagi,Ken-Ichi Kurotani,Takashi Araki,José L Pruneda-Paz,Ghislain Breton,Steve A Kay,Asuka Higo

doi:10.1105/tpc.112.109090

Abstract

Plant architecture shows a large degree of developmental plasticity. Some of the key determinants are the timing of the floral transition induced by a systemic flowering signal (florigen) and the branching pattern regulated by key factors such as BRANCHED1 (BRC1). Here, we report that BRC1 interacts with the florigen proteins FLOWERING LOCUS T (FT) and TWIN SISTER OF FT (TSF) but not with TERMINAL FLOWER1, a floral repressor. FT protein induced in leaves moves into the subtended bud, suggesting that FT protein also plays a role in promotion of the floral transition in the axillary meristem (AM). The brc1-2 mutant shows an earlier floral transition in the axillary shoots compared with the wild type, suggesting that BRC1 plays a role in delaying the floral transition of the AMs. Genetic and gene expression analyses suggest that BRC1 interferes with florigen (FT and TSF) function in the AMs. Consistent with this, BRC1 ectopically expressed in the shoot apical meristem delays the floral transition in the main shoot. These results taken together suggest that BRC1 protein interacts with FT and TSF proteins and modulates florigen activity in the axillary buds to prevent premature floral transition of the AMs.

Highlights

There is a large degree of developmental plasticity in plant architecture, which is determined in part by the timing of floral transition and the branching pattern
The floral transition is induced by a systemic flowering signal, and plant architecture is often remodeled upon the floral transition in the shoot apical meristem (SAM)
Because some TCP family members were not represented in the two transcription factor (TF) libraries, we performed yeast two-hybrid assays with the individual TCP transcriptional factors that have been reported to be involved in various developmental processes

Summary

Introduction

There is a large degree of developmental plasticity in plant architecture, which is determined in part by the timing of floral transition and the branching pattern. In the rosette-forming plant Arabidopsis thaliana, floral transition is followed by rapid internode elongation and activation of axillary bud development in inductive long-day (LD) conditions. Since axillary bud development proceeds differently than that of the main shoot, the systemic. Appropriate regulation of axillary bud development is achieved through integrating internal and environmental signals at each of the three developmental stages: axillary meristem (AM) initiation, bud differentiation, and shoot elongation. AM initiation requires the GRAS family gene LATERAL SUPPRESOR (Schumacher et al, 1999; Greb et al, 2003) and the Myb-like transcription factor (TF) REGULATOR OF AXILLARY MERISTEM1 (Keller et al, 2006; Müller et al, 2006). Axillary shoot elongation is regulated by multiple plant hormones. Cytokinin is thought to be a secondary messenger and acts more locally in the buds to promote outgrowth

Methods

Results

Conclusion