The Role of EjSVPs in Flower Initiation in Eriobotrya japonica

Abstract

Flowering plants have evolved different flowering habits to sustain long-term reproduction. Most woody trees experience dormancy and then bloom in the warm spring, but loquat blooms in the cold autumn and winter. To explore its mechanism of flowering regulation, we cloned two <i>SHORT VEGETATIVE PHASE (SVP)</i> homologous genes from 'Jiefanzhong' loquat (<i>Eriobotrya japonica</i> Lindl.), namely, <i>EjSVP1</i> and <i>EjSVP2</i>. Sequence analysis revealed that the EjSVPs were typical MADS-box transcription factors and exhibited a close genetic relationship with other plant SVP/DORMANCY-ASSOCIATED MADS-BOX (DAM) proteins. The temporal and spatial expression patterns showed that <i>EjSVP1</i> and <i>EjSVP2</i> were mainly expressed in the shoot apical meristem (SAM) after the initiation of flowering; after reaching their highest level, they gradually decreased with the development of the flower until they could not be detected. <i>EjSVP1</i> expression levels were relatively high in young tissues, and <i>EjSVP2</i> expression levels were relatively high in young to mature transformed tissues. Interestingly, <i>EjSVP2</i> showed relatively high expression levels in various flower tissues. We analyzed the <i>EjSVP</i> promoter regions and found that they did not contain the C-repeat/dehydration-responsive element. Finally, we overexpressed the <i>EjSVPs</i> in wild-type <i>Arabidopsis thaliana</i> Col-0 and found no significant changes in the number of rosette leaves of <i>Arabidopsis thaliana</i>; however, overexpression of <i>EjSVP2</i> affected the formation of <i>Arabidopsis thaliana</i> flower organs. In conclusion, <i>EjSVPs</i> were found to play an active role in the development of loquat flowering. These findings may provide a reference for exploring the regulation mechanisms of loquat flowering and the dormancy mechanisms of other plants.