Functional Redundancy of FLOWERING LOCUS T 3b in Soybean Flowering Time Regulation.

Qiang Su,Yingying Chen,Min Li,Li Chen,Wensheng Hou,Yupeng Cai,Shi Sun,Tianfu Han,Shan Yuan,Jialing Zhang

doi:10.3390/ijms23052497

Abstract

Photoperiodic flowering is an important agronomic trait that determines adaptability and yield in soybean and is strongly influenced by FLOWERING LOCUS T (FT) genes. Due to the presence of multiple FT homologs in the genome, their functions in soybean are not fully understood. Here, we show that GmFT3b exhibits functional redundancy in regulating soybean photoperiodic flowering. Bioinformatic analysis revealed that GmFT3b is a typical floral inducer FT homolog and that the protein is localized to the nucleus. Moreover, GmFT3b expression was induced by photoperiod and circadian rhythm and was more responsive to long-day (LD) conditions. We generated a homozygous ft3b knockout and three GmFT3b-overexpressing soybean lines for evaluation under different photoperiods. There were no significant differences in flowering time between the wild-type, the GmFT3b overexpressors, and the ft3b knockouts under natural long-day, short-day, or LD conditions. Although the downstream flowering-related genes GmFUL1 (a, b), GmAP1d, and GmLFY1 were slightly down-regulated in ft3b plants, the floral inducers GmFT5a and GmFT5b were highly expressed, indicating potential compensation for the loss of GmFT3b. We suggest that GmFT3b acts redundantly in flowering time regulation and may be compensated by other FT homologs in soybean.

Highlights

The change from vegetative to reproductive growth is a critical developmental transition in the life of flowering plants
We found that GmFT3b redundantly participated in soybean photoperiodic flowering
The results suggested that GmFT3b expression was regulated by circadian rhythm and was more sensitive to the induced LD photoperiod compared to the SD

Summary

Introduction

The change from vegetative to reproductive growth is a critical developmental transition in the life of flowering plants. In Arabidopsis thaliana, a long-day (LD) plant, flowering is induced by external and endogenous cues such as photoperiod, gibberellin levels, vernalization, and autonomous flowering signaling [4]. Among these cues, photoperiodical variation directly affects flowering time and the podding stage and time to maturity [5]. In Arabidopsis, florigen is the key regulatory integration factor in flowering induction pathways [7]. Several photoperiodical regulatory pathways determine flowering: GIGANTEA (GI), CONSTANS (CO), and FT function as central components in triggering flowering under LD conditions [7,8,9]. The circadian clock GI activates CO expression by binding to its promoter under LD photoperiod conditions, but not under short-day (SD)

Methods

Results

Discussion

Conclusion