Ectopic expression of an Eriobotrya japonica APETALA3 ortholog rescues the petal and stamen identities in Arabidopsis ap3-3 mutant.

APETALA3: (AP3) encodes a floral homeotic class B-function MADS-box protein and plays crucial roles in petal and stamen development. To better understand the functional roles of AP3 orthologs in Eriobotrya, we isolated and identified an AP3 ortholog, referred to as EjAP3, from Eriobotrya japonica. Analyses of protein sequence and phylogenetic tree showed that the EjAP3 was assigned to the rosids euAP3 lineage and included a distinctive PI-derived and euAP3 motifs at the C-terminal domain. Subcellular localization of EjAP3 was determined to be in the nucleus. Expression analysis suggested that EjAP3 expression was restricted only in petals and stamens, but not in sepals and carpels. Importantly, during the floral development, EjAP3 expression level was the highest at the stage of visible floral bud. Furthermore, ectopic expression of EjAP3 in Arabidopsis ap3-3 mutant rescued the second whorl petals and the third whorl stamens. The expression pattern and function characterization of EjAP3 contribute to better understand the roles of AP3 orthologs in Eriobotrya.