The AtERF19 gene regulates meristem activity and flower organ size in plants

SUMMARY Ethylene‐responsive factors (ERFs) have diverse functions in the regulation of various plant developmental processes. Here, we demonstrate the dual role of an Arabidopsis ERF gene, AtERF19 , in regulating reproductive meristem activity and flower organ size through the regulation of genes involved in CLAVATA–WUSCHEL (CLV–WUS) and auxin signaling, respectively. We found that AtERF19 stimulated the formation of flower primordia and controlled the number of flowers produced by activating WUS and was negatively regulated by CLV3 . 35S:: AtERF19 expression resulted in significantly more flowers, whereas 35S:: AtERF19 + SRDX dominant‐negative mutants produced fewer flowers. In addition, AtERF19 also functioned to control flower organ size by promoting the division/expansion of the cells through activating Small Auxin Up RNA Gene 32 ( SAUR32 ), which positively regulated MYB21 / 24 in the auxin signaling pathway. 35S:: AtERF19 and 35S:: SAUR32 resulted in similarly larger flowers, whereas 35S:: AtERF19 + SRDX and 35S:: SAUR32‐RNAi mutants produced smaller flowers than the wild type. The functions of AtERF19 were confirmed by the production of similarly more and larger flowers in 35S:: AtERF19 transgenic tobacco ( Nicotiana benthamiana ) and in transgenic Arabidopsis which ectopically expressed the orchid gene ( Nicotiana benthamiana ) PaERF19 than in wild‐type plants. The finding that AtERF19 regulates genes involved in both CLV–WUS and auxin signaling during flower development significantly expands the current knowledge of the multifunctional evolution of ERF genes in plants. The results presented in this work indicate a dual role for the transcription factor AtERF19 in controlling the number of flowers produced and flower organ size through the regulation of genes involved in CLV–WUS and auxin signaling, respectively. Our findings expand the knowledge of the roles of ERF genes in the regulation of reproductive development.