Divergent roles of FT-like 9 in flowering transition under different day lengths in Brachypodium distachyon

Zhengrui Qin,Sajid Muhammad,Hailong An,Xia Wu,Liang Wu,Yuxue Bai,Jiajie Wu,Pingchuan Deng

doi:10.1038/s41467-019-08785-y

Zhengrui Qin, Sajid Muhammad + Show 6 more

Open Access

https://doi.org/10.1038/s41467-019-08785-y

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Abstract

Timing of reproductive transition is precisely modulated by environmental cues in flowering plants. Facultative long-day plants, including Arabidopsis and temperate grasses, trigger rapid flowering in long-day conditions (LDs) and delay flowering under short-day conditions (SDs). Here, we characterize a SD-induced FLOWERING LOCUS T ortholog, FT-like 9 (FTL9), that promotes flowering in SDs but inhibits flowering in LDs in Brachypodium distachyon. Mechanistically, like photoperiod-inductive FT1, FTL9 can interact with FD1 to form a flowering activation complex (FAC), but the floral initiation efficiency of FTL9-FAC is much lower than that of FT1-FAC, thereby resulting in a positive role for FTL9 in promoting floral transition when FT1 is not expressed, but a dominant-negative role when FT1 accumulates significantly. We also find that CONSTANS 1 (CO1) can suppress FTL9 in addition to stimulate FT1 to enhance accelerated flowering under LDs. Our findings on the antagonistic functions of FTL9 under different day-length environments will contribute to understanding the multifaceted roles of FT in fine-tune modulation of photoperiodic flowering in plants.

Highlights

Timing of reproductive transition is precisely modulated by environmental cues in flowering plants
To explore the photoperiodic responses of FT orthologs in temperate grasses, we examined the expressions of all FT-like genes at Zeitgeber time 4 (ZT4) under SDs and long-day conditions (LDs) in B. distachyon
We found that the VRN1 promoter (VRN1p)-LUC activation by FT-like 9 (FTL9) could be obviously enhanced when the FTL9 phosphatidylethanolamine binding protein (PEBP) domain was changed to that of FT1, whereas VRN1p-LUC activation by FT1 a β-Galactosidase activity

Summary

Introduction

Timing of reproductive transition is precisely modulated by environmental cues in flowering plants. Facultative long-day plants, including Arabidopsis and temperate grasses, trigger rapid flowering in long-day conditions (LDs) and delay flowering under short-day conditions (SDs). We find that CONSTANS 1 (CO1) can suppress FTL9 in addition to stimulate FT1 to enhance accelerated flowering under LDs. Our findings on the antagonistic functions of FTL9 under different day-length environments will contribute to understanding the multifaceted roles of FT in fine-tune modulation of photoperiodic flowering in plants. Facultative long-day plants, including Arabidopsis thaliana, trigger rapid flowering in long-day conditions (LDs) while delay flowering under short-day conditions (SDs)[5]. Thereby, identification of more modulators in non-inductive environments can help understanding the exact molecular pathway of flowering initiation in plants

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