GmFULc Is Induced by Short Days in Soybean and May Accelerate Flowering in Transgenic Arabidopsis thaliana.

Jingzhe Sun,Xiaoming Zhang,Zhengya Liu,Wenbin Li,Yongguo Xue,Tianmeng Liu,Mengyuan Wang,Lin Zhao,Chuanlin Zhao,Yuhuan Fan

doi:10.3390/ijms221910333

Abstract

Flowering is an important developmental process from vegetative to reproductive growth in plant; thus, it is necessary to analyze the genes involved in the regulation of flowering time. The MADS-box transcription factor family exists widely in plants and plays an important role in the regulation of flowering time. However, the molecular mechanism of GmFULc involved in the regulation of plant flowering is not very clear. In this study, GmFULc protein had a typical MADS domain and it was a member of MADS-box transcription factor family. The expression analysis revealed that GmFULc was induced by short days (SD) and regulated by the circadian clock. Compared to wild type (WT), overexpression of GmFULc in transgenic Arabidopsis caused significantly earlier flowering time, while ful mutants flowered later, and overexpression of GmFULc rescued the late-flowering phenotype of ful mutants. ChIP-seq of GmFULc binding sites identified potential direct targets, including TOPLESS (TPL), and it inhibited the transcriptional activity of TPL. In addition, the transcription levels of FLOWERING LOCUS T (FT), SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) and LEAFY (LFY) in the downstream of TPL were increased in GmFULc- overexpression Arabidopsis, suggesting that the early flowering phenotype was associated with up-regulation of these genes. Our results suggested that GmFULc inhibited the transcriptional activity of TPL and induced expression of FT, SOC1 and LFY to promote flowering.

Highlights

Soybean [Glycine max (L.) Merrill] is a typically short days (SD) plant, as its vegetative and reproductive growth are closely related to the photoperiod [1]
The soybean switches from vegetative growth to reproductive growth only after the length of daylight is shortened to a critical limit
Due to the photoperiod sensitivity characteristic of soybean, when it is planted at higher latitudes, where it is exposed to long-day (LD) conditions in the growing season, they often show late flowering, the growth period is prolonged, and they might not even flower or mature normally; when it is planted at lower latitudes, where it is exposed to shortened lengths of daylight in the growing season, it generally shows early flowering, shortening of the growing period, reduction of yield and even failure of normal growth

Summary

Introduction

Soybean [Glycine max (L.) Merrill] is a typically SD plant, as its vegetative and reproductive growth are closely related to the photoperiod [1]. Due to the photoperiod sensitivity characteristic of soybean, when it is planted at higher latitudes, where it is exposed to long-day (LD) conditions in the growing season, they often show late flowering, the growth period is prolonged, and they might not even flower or mature normally; when it is planted at lower latitudes, where it is exposed to shortened lengths of daylight in the growing season, it generally shows early flowering, shortening of the growing period, reduction of yield and even failure of normal growth. Many members of the MADS-box transcription factor family, which play key roles in plant development processes, including flowering induction, flowering time, formation of floral meristems and organs, fruit formation and seed pigmentation, such as FUL, APETALA1 (AP1), CAULIFLOWER (CAL), SEPALLATA (SEP) 1/2/3 and AGAMOUS (AG), are involved in the formation of flowers, and MADS-box proteins can form heterodimers with other proteins to regulate flowering [5,6,7]. FT is transported to the apical meristems, triggering the expression of FUL and SOC1 in the apical meristems

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