CpWRKY71, a WRKY Transcription Factor Gene of Wintersweet (Chimonanthus praecox), Promotes Flowering and Leaf Senescence in Arabidopsis

The WRKY transcription factors are one of the most important plant-specific transcription factors and play vital roles in various biological processes. However, the functions of WRKY genes in wintersweet (Chimonanthus praecox) are still unknown. In this report, a group IIc WRKY gene, CpWRKY71, was isolated from wintersweet. CpWRKY71 was localized to the nucleus and possessed transcriptional activation activity. qRT-PCR (quantitative real-time PCR) analysis showed that CpWRKY71 was expressed in all tissues tested, with higher expression in flowers and senescing leaves. During the flower development, the highest expression was detected in the early-withering stage, an obvious expression of CpWRKY71 was also observed in the flower primordia differentiation and the bloom stage. Meanwhile, the expression of CpWRKY71 was influenced by various abiotic stress and hormone treatments. The expression patterns of the CpWRKY71 gene were further confirmed in CpWRKY71pro:GUS (β-glucuronidase) plants. Heterologous overexpression of CpWRKY71 in Arabidopsis caused early flowering. Consistent with the early flowering phenotype, the expression of floral pathway integrators and floral meristem identity (FMI) genes were significantly up-regulated in transgenic plants. In addition, we also observed that the transgenic plants of CpWRKY71 exhibited precocious leaf senescence. In conclusion, our results suggested that CpWRKY71 may be involved in the regulation of flowering and leaf senescence in Arabidopsis. Our study provides a foundation for further characterization of CpWRKY genes function in wintersweet, and also enrich our knowledge of molecular mechanism about flowering and senescence in wintersweet.