EjFRI, FRIGIDA (FRI) Ortholog from Eriobotrya japonica, Delays Flowering in Arabidopsis.

Weiwei Chen,Qigao Guo,Peng Wang,Guolu Liang,Dan Wang,Danlong Jing,Jiangbo Dang,Qiao He,Yan Xia,Min Shi

doi:10.3390/ijms21031087

Abstract

In the model species Arabidopsis thaliana, FRIGIDA (FRI) is a key regulator of flowering time and can inhibit flowering without vernalization. However, little information is available on the function in the Rosaceae family. Loquat (Eriobotrya japonica) belongs to the family Rosaceae and is a distinctive species, in which flowering can be induced without vernalization, followed by blooming in late-autumn or winter. To investigate the functional roles of FRI orthologs in this non-vernalization species, we isolated an FRI ortholog, dubbed as EjFRI, from loquat. Analyses of the phylogenetic tree and protein sequence alignment showed that EjFRI is assigned to eurosids I FRI lineage. Expression analysis revealed that the highest expression level of EjFRI was after flower initiation. Meanwhile, EjFRI was widely expressed in different tissues. Subcellular localization of EjFRI was only detected to be in the nucleus. Ectopic expression of EjFRI in wild-type Arabidopsis delayed flowering time. The expression levels of EjFRI in transgenic wild-type Arabidopsis were significantly higher than those of nontransgenic wild-type lines. However, the expression levels of AtFRI showed no significant difference between transgenic and nontransgenic wild-type lines. Furthermore, the upregulated AtFLC expression in the transgenic lines indicated that EjFRI functioned similarly to the AtFRI of the model plant Arabidopsis. Our study provides a foundation to further explore the characterization of EjFRI, and also contributes to illuminating the molecular mechanism about flowering in loquat.

Highlights

Flowering is a crucial phase during the life cycle of angiosperms
FRI serving as the determinant of flowering time has been deeply and extensively studied in the model plant, the functional characterization of FRI in horticulture plants, especially the fruit trees, needs further research
The expression levels of AtFLC were upregulated in transgenic plants (Figure 5E). These results indicated that EjFRI delayed flowering time in Arabidopsis and contributed to upregulating the AtFLC

Summary

Introduction

Flowering is a crucial phase during the life cycle of angiosperms. At present, the comprehensive flowering network is approached in the model plant species Arabidopsis thaliana, and extensive studies have been performed to describe related pathways of flower development [1]. Some regulatory genes of flowering time have been isolated and characterized from loquat, including EjSOC1, EjFT, EjFD, EjGI, EjSVP, EjCO, EjAP1, EjTFL1 and EjLEY [3,4,5,6,7,8,9]. Among these genes, orthologous genes of the floral integrators, such as EjFT and EjSOC1, are identified and reported to regulate plant flowering-time by adjusting the environmental and endogenous pathways, including circadian clock regulation, photoreception, growth regulator of synthesis and response, and response to low temperatures [2,10,11]. FRI serving as the determinant of flowering time has been deeply and extensively studied in the model plant, the functional characterization of FRI in horticulture plants, especially the fruit trees, needs further research

Methods

Results

Discussion

Conclusion