Overexpressing BrWRKY22 Delays Flowering and Leaf Senescence via Inhibition of GA Biosynthesis in Brassica rapa
2025
Junaite Bin Gias Uddin | Tingzhen Zhuo | Xiaojie Li | Xuan Wu | Zhuoyu Wu | Habiba | Yujun Ren | Ying Miao
WRKY transcription factors play a predominant role in plant stress responses, as well as growth and development. Although WRKY genes have been extensively studied in model plants, little is known about them in Brassica rapa. In this study, the BrWRKY22 gene was isolated and characterized. BrWRKY22 is nuclear localized and has self-activation and dimerization activity. BrWRKY22 was highly expressed in young leaves, roots, and stems. The overexpressed BrWRKY22 :Arabidopsis and Brassica rapa lines exhibited a dwarfish, delayed flowering and leaf senescence phenotype compared to the wild-type (WT). Molecular evidence showed that the transcript levels of BrCHLP are increased, whereas those of BrLFY, BrSOC1, BrGA20OX2, BrGA3OX1, and BrGASA6 are significantly decreased in BrWRKY22 overexpressing plants compared to the WT. BrWRKY22 can bind directly to the promoters of BrCHLP and BrGA20OX2, activating BrCHLP and repressing BrGA20OX2 gene transcription. The chlorophyll b and tocopherol levels are increased, whereas the GA and ABA levels are significantly decreased, in three-week-old BrWRKY22 overexpressing Brassica 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 Brassica rapa plant development.
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