The Role of EjSOC1s in Flower Initiation in Eriobotrya japonica.

Yuanyuan Jiang,Yunmei Zhu,Wenbing Su,Yongshun Gao,Shunquan Lin,Ling Zhang,Yi Jing,Jiangrong Peng

doi:10.3389/fpls.2019.00253

Abstract

The MADS-box transcription factor SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) integrates environmental and endogenous signals to promote flowering in Arabidopsis. However, the role of SOC1 homologs in regulating flowering time in fruit trees remains unclear. To better understand the molecular mechanism of flowering regulation in loquat (Eriobotrya japonica Lindl.), two SOC1 homologs (EjSOC1-1 and EjSOC1-2) were identified and characterized in this work. Sequence analysis showed that EjSOC1-1 and EjSOC1-2 have conserved MADS-box and K-box domains. EjSOC1-1 and EjSOC1-2 were clearly expressed in vegetative organs, and high expression was detected in flower buds. As observed in paraffin-embedded sections, expression of the downstream flowering genes EjAP1s and EjLFYs started to increase at the end of June, a time when flower bud differentiation occurs. Additionally, high expression of EjSOC1-1 and EjSOC1-2 began 10 days earlier than that of EjAP1s and EjLFYs in shoot apical meristem (SAM). EjSOC1-1 and EjSOC1-2 were inhibited by short-day (SD) conditions and exogenous GA3, and flower bud differentiation did not occur after these treatments. EjSOC1-1 and EjSOC1-2 were found to be localized to the nucleus. Moreover, ectopic overexpression of EjSOC1-1 and EjSOC1-2 in wild-type Arabidopsis promoted early flowering, and overexpression of both was able to rescue the late flowering phenotype of the soc1-2 mutant. In conclusion, the results suggest that cultivated loquat flower bud differentiation in southern China begins in late June to early July and that EjSOC1-1 and EjSOC1-2 participate in the induction of flower initiation. These findings provide new insight into the artificial regulation of flowering time in fruit trees.

Highlights

Plant evolution has resulted in a variety of endogenous and exogenous factors that form a complex and sophisticated regulatory network to accurately respond to internal and external signals and integrate them to promote blooming at the most favorable time
The results showed a high level of expression for both EjAP1s and EjLFYs began on June 23rd that was maintained from July to September (Figure 1C), except for EjLFY-2, which maintained a peak until November
AP1 and LFY determine flower meristem characteristics and are key genes for flower induction and morphology (Lohmann et al, 2001). These results indicate that “Jiefangzhong” loquat flower bud differentiation in Guangzhou begins in late June to early July

Summary

Introduction

Plant evolution has resulted in a variety of endogenous and exogenous factors that form a complex and sophisticated regulatory network to accurately respond to internal and external signals and integrate them to promote blooming at the most favorable time. The molecular genetic mechanisms at play in annual flowering plants, such as Arabidopsis thaliana, involve multiple regulatory pathways, including photoperiod, age, autonomic, vernalization, and gibberellin pathways (Moon et al, 2005; Amasino, 2010; Srikanth and Schmid, 2011; Teotia and Tang, 2015). SOC1 plays a vital role in regulating plant development and flower organogenesis by integrating photoperiod, age, and gibberellin signals (Parcy, 2005; Lee and Lee, 2010; Teotia and Tang, 2015)

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Results

Conclusion