The AP2/ERF Transcription Factor ERF56 Negatively Regulating Nitrate-Dependent Plant Growth in Arabidopsis

ERF56, a member of the APETALA2/ETHYLENE-RESPONSIVE FACTOR (AP2/ERF) transcription factor (TF) family, was reported to be an early nitrate-responsive TF in Arabidopsis. But the function of ERF56 in nitrate signaling remains not entirely clear. This study aimed to investigate the role of ERF56 in nitrate-dependent plant growth and nitrate signaling. We confirmed with reverse transcription quantitative PCR (RT-qPCR) that the transcription of ERF56 is quickly induced by nitrate. ERF56 overexpressors displayed decreased nitrate-dependent plant growth, while erf56 mutants exhibited increased plant growth. Confocal imaging demonstrated that ERF56 is localized into nuclei. Assays with the glucuronidase (GUS) reporter showed that ERF56 is mainly expressed at the region of maturation of roots and in anthers. The dual-luciferase assay manifested that the transcription of ERF56 is not directly regulated by NIN-LIKE PROTEIN 7 (NLP7). The transcriptome analysis identified 1038 candidate genes regulated by ERF56 directly. A gene ontology (GO) over-representation analysis showed that ERF56 is involved in the processes of water transport, inorganic molecule transmembrane transport, secondary metabolite biosynthesis, and cell wall organization. We revealed that ERF56 represses nitrate-dependent growth through regulating the processes of inorganic molecule transmembrane transport, the secondary metabolite biosynthesis, and cell wall organization.