A group VIIIa ethylene-responsive factor, CmERF4, negatively regulates waterlogging tolerance in chrysanthemum.

Ethylene-responsive factors (ERF) play an important role in plant responses to waterlogging stress. However, the function and mechanism of action of ERFVIII in response to waterlogging stress remain poorly understood. In this study, we found that the ERF VIIIa gene CmERF4 in chrysanthemum was induced by waterlogging stress. CmERF4 is localized to the nucleus in tobacco leaves. Yeast two-hybrid (Y2H) and dual-luciferase assays showed that CmERF4 is a transcriptional inhibitor. CmERF4 overexpression in chrysanthemum reduced plant waterlogging tolerance, whereas the expression of the chimeric activator CmERF4-VP64 promoted higher waterlogging tolerance than that observed in wild-type plants, indicating that CmERF4 negatively regulates waterlogging tolerance in chrysanthemum. Transcriptome profiling showed that energy metabolism and reactive oxygen species (ROS) pathway-associated genes were differentially expressed between CmERF4-VP64 and wild-type plants. An RT-qPCR assay showed that the gene expression patterns were consistent with the expression levels obtained from RNA-seq analysis. Overall, we identified new functions of CmERF4 which negatively regulates chrysanthemum waterlogging tolerance by modulating energy metabolism and ROS pathway genes.