Overexpression of DREB2C Delays Flowering in Arabidopsis thaliana via the Activation of FLC

Abstract

The timing of vegetative-to-reproductive phase transition changes under a variety of stresses. Here, we investigated the role of dehydration-responsive element-binding factor 2C (DREB2C), one of the high-temperature stress signaling transcription factors, in flowering in Arabidopsis thaliana. DREB2C-overexpressing Arabidopsis plants displayed delayed flowering relative to the wild type, and this phenotype was correlated with the upregulation of the FLOWERING LOCUS C (FLC) gene, which encodes a potent floral repressor. The FLC promoter harbors a putative dehydration-responsive element (DRE), which is the binding site of DREB transcription factors. Electrophoretic mobility shift assays (EMSAs) revealed that DREB2C binds directly to the FLC promoter. Transient promoter activation assays using Arabidopsis mesophyll protoplasts showed that DREB2C acts as a transcriptional activator of FLC. In addition, DREB2C-overexpressors exhibited short stamen filaments, leading to reduced pollination and consequently less seed production compared with the wild type. The expression of the beta-glucuronidase (GUS) gene, driven by the DREB2C promoter, was abruptly induced at floral stage 13, as measured by GUS staining analysis, and the elongation of stamen filaments was simultaneously arrested. Together, these results indicate that DREB2C plays a multifaceted role in floral transition modulation and stamen filament elongation.