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

TITLE=The Role of EjSOC1s in Flower Initiation in Eriobotrya japonica

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00253

DOI=10.3389/fpls.2019.00253

ISSN=1664-462X

ABSTRACT=<p>The MADS-box transcription factor SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (<italic>SOC1</italic>) integrates environmental and endogenous signals to promote flowering in <italic>Arabidopsis</italic>. However, the role of <italic>SOC1</italic> homologs in regulating flowering time in fruit trees remains unclear. To better understand the molecular mechanism of flowering regulation in loquat (<italic>Eriobotrya japonica</italic> Lindl.), two <italic>SOC1</italic> homologs (<italic>EjSOC1-1</italic> and <italic>EjSOC1-2</italic>) were identified and characterized in this work. Sequence analysis showed that EjSOC1-1 and EjSOC1-2 have conserved MADS-box and K-box domains. <italic>EjSOC1-1</italic> and <italic>EjSOC1-2</italic> 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 <italic>EjAP1</italic>s and <italic>EjLFY</italic>s started to increase at the end of June, a time when flower bud differentiation occurs. Additionally, high expression of <italic>EjSOC1-1</italic> and <italic>EjSOC1-2</italic> began 10 days earlier than that of <italic>EjAP1</italic>s and <italic>EjLFY</italic>s in shoot apical meristem (SAM). <italic>EjSOC1-1</italic> and <italic>EjSOC1-2</italic> were inhibited by short-day (SD) conditions and exogenous GA<sub>3</sub>, 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 <italic>EjSOC1-1</italic> and <italic>EjSOC1-2</italic> in wild-type <italic>Arabidopsis</italic> promoted early flowering, and overexpression of both was able to rescue the late flowering phenotype of the <italic>soc1-2</italic> mutant. In conclusion, the results suggest that cultivated loquat flower bud differentiation in southern China begins in late June to early July and that <italic>EjSOC1-1</italic> and <italic>EjSOC1-2</italic> participate in the induction of flower initiation. These findings provide new insight into the artificial regulation of flowering time in fruit trees.</p>