Identification and Functional Characterization of FLOWERING LOCUS T in Platycodon grandiflorus.

Gayeon Kim,Hyunwoo Cho,Yeonggil Rim,Tae Kyung Hyun

doi:10.3390/plants11030325

Gayeon Kim, Hyunwoo Cho + Show 2 more

Open Access

https://doi.org/10.3390/plants11030325

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Abstract

Platycodon grandiflorus roots have been used as a foodstuff and traditional medicine for thousands of years in East Asia. In order to increase the root development of P. grandiflorus, cultivators removed the inflorescences, suggesting the possible negative effect of flowering on root development. This indicates that the genetic improvement of P. grandiflorus by late flowering is a potential approach to increase productivity. However, nothing is known about key genes integrating multiple flowering pathways in P. grandiflorus. In order to fill this gap, we identified potential homologs of the FLOWERING LOCUS T (FT) gene in P. grandiflorus. The alignment with other FT members and phylogenetic analysis revealed that the P. grandiflorus FT (PlgFT) protein contains highly conserved functional domains and belongs to the FT-like clade. The expression analysis revealed spatial variations in the transcription of PlgFT in different organs. In addition, the expression level of PlgFT was increased by high temperature but not by photoperiodic light input signals, presumably due to lacking the CONSTANS binding motif in its promoter region. Furthermore, PlgFT induced early flowering upon its overexpression in P. grandiflorus, suggesting the functional role of PlgFT in flowering. Taken together, we functionally characterized PlgFT as a master regulator of P. grandiflorus flowering under inductive high temperature, which will serve as an important target gene for improving the root productivity.

Highlights

The transition from vegetative to the reproductive stage is a critical event in plant development
These findings indicate the importance of ambient temperature to induce flowering
Arabidopsis FLOWERING LOCUS T (FT) exhibits protein sequence similarity of ~60% with Arabidopsis TERMINAL FLOWER 1 (TFL1), they function in an opposite manner [21,27]

Summary

Introduction

The transition from vegetative to the reproductive stage is a critical event in plant development. At the Arabidopsis SAM, FT physically interacts with basic leucine-zipper (bZIP)-type transcription factor FLOWERING LOCUS D (FD) and 14-3-3 proteins. These interactors form florigen activation complex (FAC) in Arabidopsis to promote the floral meristem identity genes such as APETALA1 (AP1) [5] and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) [6] either directly or indirectly. The Arabidopsis FT homolog FT-like (Narcissus FLOWERING LOCUS T1) NFT1 gene was up-regulated by heat treatment (30 ◦C) and promoted flower initiation [14] These findings indicate the importance of ambient temperature to induce flowering

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