Overexpressing Delays Flowering and Leaf Senescence via Inhibition of GA Biosynthesis in .

WRKY transcription factors play a predominant role in plant stress responses, as well as growth and development. Although genes have been extensively studied in model plants, little is known about them in . In this study, the gene was isolated and characterized. BrWRKY22 is nuclear localized and has self-activation and dimerization activity. was highly expressed in young leaves, roots, and stems. The overexpressed and lines exhibited a dwarfish, delayed flowering and leaf senescence phenotype compared to the wild-type (WT). Molecular evidence showed that the transcript levels of are increased, whereas those of , , , , and are significantly decreased in overexpressing plants compared to the WT. BrWRKY22 can bind directly to the promoters of and , activating and repressing gene transcription. The chlorophyll b and tocopherol levels are increased, whereas the GA and ABA levels are significantly decreased, in three-week-old overexpressing lines compared to the WT. Collectively, our results suggest that BrWRKY22 directly controls chlorophyll b and GA biosynthesis and plays a repressive role in leaf senescence and the initiation of flowering in plant development.