Chrysanthemum embryo development is negatively affected by a novel ERF transcription factor, CmERF12

Embryo abortion often occurs during distant hybridization events. Apetala 2/ethylene-responsive factor (AP2/ERF) proteins are key transcription factor (TF) regulators of plant development and stress resistance, but their roles in hybrid embryo development are poorly understood. We isolated a novel AP2/ERF TF, CmERF12, from chrysanthemum and showed that it adversely affects embryo development during distant hybridization. Transcriptome and real-time quantitative PCR data demonstrated that CmERF12 is expressed at significantly higher levels in aborted ovaries compared with normal ovaries. CmERF12 localizes to the cell nucleus and contains a conserved EAR motif that mediates its transcription repressor function in yeast and plant cells. We generated an amiR-CmERF12 transgenic Chrysanthemum morifolium (C.m.) var. 'Yuhualuoying' and conducted distant hybridization with the wild-type tetraploid, Chrysanthemum nankingense (C.n.), revealing that CmERF12 knockdown significantly promoted embryo development and increased the seed setting rates during hybridization. The expression of various embryo development-related genes was up-regulated in developing ovaries from the ♀amiR-CmERF12-C.m. × ♂C.n. cross. Furthermore, CmERF12 directly interacted with CmSUF4 and significantly reduced its ability to activate its target gene CmEC1. Overall, we invented an original method to overcome plant distant hybridization barriers and unraveled the mechanism by which CmERF12 negatively affects chrysanthemum embryo development.