TERMINAL FLOWER1 Functions as a Mobile Transcriptional Cofactor in the Shoot Apical Meristem.

Daniela Goretti,Carla Méndez,Francisco Madueño,Silvio Collani,Marina Silvestre,Tobias Langenecker,Markus Schmid

doi:10.1104/pp.19.00867

Abstract

The floral transition is a critical step in the life cycle of flowering plants, and several mechanisms control this finely orchestrated process. TERMINAL FLOWER1 (TFL1) is a floral repressor and close relative of the florigen, FLOWERING LOCUS T (FT). During the floral transition, TFL1 expression is up-regulated in the inflorescence apex to maintain the indeterminate growth of the shoot apical meristem (SAM). Both TFL1 and FT are mobile proteins, but they move in different ways. FT moves from the leaves to the SAM, while TFL1 appears to move within the SAM. The importance of TFL1 movement for its function in the regulation of flowering time and shoot indeterminacy and its molecular function are still largely unclear. Our results using Arabidopsis (Arabidopsis thaliana) indicate that TFL1 moves from its place of expression in the center of the SAM to the meristem layer L1 and that the movement in the SAM is required for the regulation of the floral transition. Chromatin immunoprecipitation sequencing and RNA sequencing demonstrated that TFL1 functions as a cotranscription factor that associates with and regulates the expression of hundreds of genes. These newly identified direct TFL1 targets provide the possibility to discover new roles for TFL1 in the regulation of floral transition and inflorescence development.

Highlights

shoot apical meristem (SAM), while TERMINAL FLOWER1 (TFL1) appears to move within the SAM
FLOWERING LOCUS T (FT) is a member of the phosphatidylethanolaminebinding protein (PEBP) family, which in Arabidopsis is composed of six members that fall into three major clades: MOTHER OF FT (MFT)-like, FT-like, and TERMINAL FLOWER1 (TFL1)-like (Karlgren et al, 2011)
Late flowering was observed in the 35S constitutive promoter (35Spro)::TFL1-1xVenus and 35Spro::TFL1-3xVenus lines (Fig. 1D; Supplemental Fig. S3, D–F), indicating that the presence of C-terminal 1xVenus or 3xVenus tags did not affect the ability of TFL1 to repress flowering and that the TFL1 protein retained activity irrespective of the size of the tag

Summary

Introduction

SAM, while TFL1 appears to move within the SAM. The importance of TFL1 movement for its function in the regulation of flowering time and shoot indeterminacy and its molecular function are still largely unclear. The main representative of the third PEBP protein subgroup is TFL1, and it inhibits flowering as do the two other members of the clade, ARABIDOPSIS THALIANA CENTRORADIALIS homolog (ATC) and BROTHER OF FT (BFT; Mimida et al, 2001; Yoo et al, 2010). Both ATC and BFT have been shown to interact with FD and to repress APETALA1 (AP1) expression (Huang et al, 2012; Ryu et al, 2014). Its role as a flowering time regulator is further confirmed by the late-flowering phenotype of 35Spro::TFL1 plants (Ratcliffe et al, 1998)

Methods

Results

Discussion

Conclusion