Gibberellins (GAs) are phytohormones (植物激素) that regulate many aspects of plant growth and development, including germination (萌发), elongation, flowering, and floral development. Negative feedback regulation (负反馈调节) contributes to homeostasis (动态平衡) of the GA level. DELLAs are negative regulators of GA signaling and are rapidly degraded in the presence of GAs. DELLAs regulate many target genes, including AtGA20ox2, encoding the GA-biosynthetic enzyme GA 20-oxidase (氧化酶). As DELLAs do not have an apparent DNA-binding motif, transcription factors that act in association with DELLA are necessary for regulating the target genes. Previous studies have identified GAI-ASSOCIATED FACTOR 1 (GAF1) as such a DELLA interactor, with which DELLAs act as coactivators (共激活因子), and AtGA20ox2 was identified as a target gene of the DELLA-GAF1 complex. In this study, electrophoretic mobility shift (电泳迁移率改变) and chromatin immunoprecipitation assays (染色质免疫沉淀) showed that four GAF1-binding sites exist in the AtGA20ox2 promoter. Using transgenic plants, we further evaluated the contribution of the DELLA-GAF1 complex to GA feedback regulation. Mutations in four GAF1-binding sites abolished the negative feedback of AtGA20ox2 in transgenic plants. Our results showed that GAF1-binding sites are necessary for GA feedback regulation of AtGA20ox2, suggesting that the DELLA-GAF1 complex is a main component of the GA feedback regulation of AtGA20ox2.

First Published data: September 15, 2017.